Publications by authors named "Mehdi Razavi"

116 Publications

An initial ex vivo evaluation of temperature profile and thermal injury formation on the epiesophageal surface during radiofrequency ablation.

J Cardiovasc Electrophysiol 2021 Jan 21. Epub 2021 Jan 21.

Electrophysiology Clinical Research and Innovations, Texas Heart Institute, Houston, Texas, USA.

Introduction: Few studies have examined heat transfer and thermal injury on the epiesophageal surface during radiofrequency application, or compared the risk of esophageal thermal injury between standard and high-power, short-duration (HPSD) ablation. We studied the thermodynamics of HPSD and standard ablation at different tissue interfaces between the left atrium and esophagus, focusing on epiesophageal temperature changes and thermal injury.

Methods And Results: Fresh porcine heart and esophageal sections were secured to a custom holder and submerged in a temperature-controlled, circulating water bath. During ablation, thermistors recorded temperatures at the catheter tip-atrial interface, epiesophageal-atrial interface, and esophageal lumen. Samples were ablated in triplicate with the following parameters: contact force (15/25g), power (10/20/30 W standard; 40/45/50 W HPSD), and duration (10/20/30 s standard; 5/10/15 s HPSD). Epiesophageal and endoluminal temperature rises were greater in HPSD than in standard ablation (epiesophageal: 5.9 ± 5.6 vs. 2.2 ± 2.0°C, p < .01; endoluminal: 0.7 ± 0.5 vs. 0.4 ± 0.2°C, p < .01). Six of 30 HPSD ablations and 1 of 26 standard ablations caused esophageal injury. The delay between the peak epiesophageal and endoluminal temperatures was greater in HPSD than in standard ablation (24.2 ± 22.1 vs. 13.0 ± 11.0 s, p = .023). Likewise, the peak epiesophageal surface temperature differed more from the concurrent endoluminal temperature in HPSD ablation (5.1 ± 5.3 vs. 1.7 ± 2.0°C, p < .01).

Conclusion: Endoluminal temperature underestimates epiesophageal surface temperature substantially during HPSD ablation. Visible epiesophageal injury was associated with a 2.2 ± 2.1°C rise in endoluminal temperature, corresponding to a 10.2 ± 6.5°C rise in epiesophageal temperature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jce.14911DOI Listing
January 2021

Platypnea-Orthodeoxia Syndrome Caused by an Intracardiac Shunt.

Tex Heart Inst J 2020 Aug;47(4):298-301

Department of Medicine, Texas Heart Institute and Baylor-St. Luke's Medical Center; Houston, Texas 77030.

Platypnea-orthodeoxia syndrome, a rare condition characterized by posture-related dyspnea, is usually caused by an intracardiac shunt, hepatopulmonary syndrome, or shunting resulting from severe pulmonary disease. We report the case of a 33-year-old woman who presented with increasing dyspnea and oxygen desaturation when she sat up or arose. Our diagnosis was platypnea-orthodeoxia syndrome. A lead of a previously implanted pacemaker exacerbated a severe tricuspid regurgitant jet that was directed toward the patient's intra-atrial septum. Percutaneous closure of a small secundum atrial septal defect eliminated right-to-left shunting and substantially improved the patient's functional status. In addition to this case, we discuss this unusual condition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.14503/THIJ-16-6094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7819445PMC
August 2020

Alcohol Ablation of Cardiac Tissues Quantified and Evaluated Using CIELAB Euclidean Distances.

Tex Heart Inst J 2020 Aug;47(4):265-270

Electrophysiology Clinical Research and Innovations, Texas Heart Institute, Houston, Texas 77030.

Ethanol solubilizes cell membranes, making it useful for various ablation applications. We examined the effect of time and alcohol type on the extent of ablation, quantified as Euclidean distances between color coordinates. We obtained biopsy punch samples (diameter, 6 mm) of left atrial appendage, atrial, ventricular, and septal tissue from porcine hearts and placed them in transwell plates filled with ethanol or methanol for 10, 20, 30, 40, 50, or 60 min. Control samples were taken for each time point. At each time point, samples were collected, cut transversely, and photographed. With use of a custom MATLAB program, all images were analyzed in the CIELAB color space, which is more perceptually uniform than the red-green-blue color space. Euclidean distances were calculated from CIELAB coordinates. The mean and standard error of these distances were analyzed. Two-way analysis of variance was used to test for differences among time points, and 2-tailed t tests, for differences between the alcohol datasets at each time point. Generally, Euclidean distances differed significantly between all time points, except for those immediately adjacent, and methanol produced larger Euclidean distances than ethanol did. Some tissue showed a plateauing effect, potentially indicating transmurality. Mean Euclidean distances effectively indexed alcohol ablation in cardiac tissue. Furthermore, we found that methanol ablated tissue more effectively than ethanol did. With ethanol, the extent of ablation for atrial tissue was largest at 60 min. We conclude that to achieve full transmurality in clinical applications, ethanol must remain in contact with atrial tissue for at least one hour.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.14503/THIJ-19-7140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7819450PMC
August 2020

Enhancing islet transplantation using a biocompatible collagen-PDMS bioscaffold enriched with dexamethasone-microplates.

Biofabrication 2021 Jan 18. Epub 2021 Jan 18.

Radiology, Stanford University School of Medicine, 3155 Porter Drive, Stanford, California, 94304, UNITED STATES.

Islet transplantation is a promising approach to enable type 1 diabetic patients to attain glycemic control independent of insulin injections. However, up to 60% of islets are lost immediately following transplantation. To improve this outcome, islets can be transplanted within bioscaffolds, however, synthetic bioscaffolds induce an intense inflammatory reaction which can have detrimental effects on islet function and survival. In the present study, we first improved the biocompatibility of polydimethylsiloxane (PDMS) bioscaffolds by coating them with collagen. To reduce the inflammatory response to PDMS bioscaffolds, we then enriched the bioscaffolds with dexamethasone-loaded microplates (DEX-µScaffolds). These DEX-microplates have the ability to release DEX in a sustained manner over 7 weeks within a therapeutic range that does not affect the glucose responsiveness of the islets but which minimizes inflammation in the surrounding microenvironment. The bioscaffold showed excellent mechanical properties that enabled it to resist pore collapse thereby helping to facilitate islet seeding and its handling for implantation, and subsequent engraftment, within the epididymal fat pad (EFP). Following the transplantation of islets into the EFP of diabetic mice using DEX-µScaffolds there was a return in basal blood glucose to normal values by day 4, with normoglycemia maintained for 30 days. Furthermore, these animals demonstrated a normal dynamic response to glucose challenges with histological evidence showing reduced pro-inflammatory cytokines and fibrotic tissue surrounding DEX-µScaffolds at the transplantation site. In contrast, diabetic animals transplanted with either islets alone or islets in bioscaffolds without DEX microplates were not able to regain glycemic control during basal conditions with overall poor islet function. Taken together, our data show that coating PDMS bioscaffolds with collagen, and enriching them with DEX-microplates, significantly prolongs and enhances islet function and survival.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1758-5090/abdcacDOI Listing
January 2021

Silicone-based bioscaffolds for cellular therapies.

Mater Sci Eng C Mater Biol Appl 2021 Feb 9;119:111615. Epub 2020 Oct 9.

Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, Department of Radiology, Palo Alto, CA 94304, USA. Electronic address:

Cellular therapy, whereby cells are transplanted to replace or repair damaged tissues and/or cells, is now becoming a viable therapeutic option to treat many human diseases. Silicones, such as polydimethylsiloxane (PDMS), consist of a biocompatible, inert, non-degradable synthetic polymer, characterized by the presence of a silicon‑oxygen‑silicon (Si-O-Si) linkage in the backbone. Silicones have been commonly used in several biomedical applications such as soft tissue implants, microfluidic devices, heart valves and 3D bioscaffolds. Silicone macroporous bioscaffolds can be made with open, interconnected pores which can house cells and facilitate the formation of a dense vascular network inside the bioscaffold to aid in its engraftment and integration into the host tissue. In this review, we will present various synthesis/fabrication techniques for silicone-based bioscaffolds and will discuss their assets and potential drawbacks. Furthermore, since cell attachment onto the surface of silicones can be limited due to their intrinsic high hydrophobicity, we will also discuss different techniques of surface modification. Finally, we will examine the physical (i.e. density, porosity, pore interconnectivity, wettability, elasticity, roughness); mechanical (tension, compression, hardness); and chemical (elemental composition-properties) properties of silicone bioscaffolds and how these can be modulated to suit the needs for specific applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.msec.2020.111615DOI Listing
February 2021

Multifunctional Conductive Biomaterials as Promising Platforms for Cardiac Tissue Engineering.

ACS Biomater Sci Eng 2021 Jan 14;7(1):55-82. Epub 2020 Dec 14.

Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, 1665659911 Tehran, Iran.

Adult cardiomyocytes are terminally differentiated cells that result in minimal intrinsic potential for the heart to self-regenerate. The introduction of novel approaches in cardiac tissue engineering aims to repair damages from cardiovascular diseases. Recently, conductive biomaterials such as carbon- and gold-based nanomaterials, conductive polymers, and ceramics that have outstanding electrical conductivity, acceptable mechanical properties, and promoted cell-cell signaling transduction have attracted attention for use in cardiac tissue engineering. Nevertheless, comprehensive classification of conductive biomaterials from the perspective of cardiac cell function is a subject for discussion. In the present review, we classify and summarize the unique properties of conductive biomaterials considered beneficial for cardiac tissue engineering. We attempt to cover recent advances in conductive biomaterials with a particular focus on their effects on cardiac cell functions and proposed mechanisms of action. Finally, current problems, limitations, challenges, and suggested solutions for applications of these biomaterials are presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsbiomaterials.0c01422DOI Listing
January 2021

A Collagen Based Cryogel Bioscaffold that Generates Oxygen for Islet Transplantation.

Adv Funct Mater 2020 Apr 20;30(15). Epub 2020 Feb 20.

Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, Department of Radiology, Palo Alto, California 94304, USA.

The aim of this work was to develop, characterize and test a novel 3D bioscaffold matrix which can accommodate pancreatic islets and provide them with a continuous, controlled and steady source of oxygen to prevent hypoxia-induced damage following transplantation. Hence, we made a collagen based cryogel bioscaffold which incorporated calcium peroxide (CPO) into its matrix. The optimal concentration of CPO integrated into bioscaffolds was 0.25wt.% and this generated oxygen at 0.21±0.02mM/day (day 1), 0.19±0.01mM/day (day 6), 0.13±0.03mM/day (day 14), and 0.14±0.02mM/day (day 21). Accordingly, islets seeded into cryogel-CPO bioscaffolds had a significantly higher viability and function compared to islets seeded into cryogel alone bioscaffolds or islets cultured alone on traditional cell culture plates; these findings were supported by data from quantitative computational modelling. When syngeneic islets were transplanted into the epididymal fat pad (EFP) of diabetic mice, our cryogel-0.25wt.%CPO bioscaffold improved islet function with diabetic animals re-establishing glycemic control. Mice transplanted with cryogel-0.25wt.%CPO bioscaffolds showed faster responses to intraperitoneal glucose injections and had a higher level of insulin content in their EFP compared to those transplanted with islets alone (P<0.05). Biodegradability studies predicted that our cryogel-CPO bioscaffolds will have long-lasting biostability for approximately 5 years (biodegradation rate: 16.00±0.65%/year). Long term implantation studies (i.e. 6 months) showed that our cryogel-CPO bioscaffold is biocompatible and integrated into the surrounding fat tissue with minimal adverse tissue reaction; this was further supported by no change in blood parameters (i.e. electrolyte, metabolic, chemistry and liver panels). Our novel oxygen-generating bioscaffold (i.e. cryogel-0.25wt.%CPO) therefore provides a biostable and biocompatible 3D microenvironment for islets which can facilitate islet survival and function at extra-hepatic sites of transplantation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adfm.201902463DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7567341PMC
April 2020

The Paracrine Function of Mesenchymal Stem Cells in Response to Pulsed Focused Ultrasound.

Cell Transplant 2020 Jan-Dec;29:963689720965478

Interventional Regenerative Medicine and Imaging Laboratory, Department of Radiology, 6429Stanford University, Palo Alto, CA, USA.

We studied the paracrine function of mesenchymal stem cells (MSCs) derived from various sources in response to pulsed focused ultrasound (pFUS). Human adipose tissue (AD), bone marrow (BM), and umbilical cord (UC) derived MSCs were exposed to pFUS at two intensities: 0.45 W/cm I (310 kPa PNP) and 1.3 W/cm I (540 kPa PNP). Following pFUS, the viability and proliferation of MSCs were assessed using a hemocytometer and confocal microscopy, and their secreted cytokine profile determined using a multiplex ELISA. Our findings showed that pFUS can stimulate the production of immunomodulatory, anti-inflammatory, and angiogenic cytokines from MSCs which was dependent on both the source of MSC being studied and the acoustic intensity employed. These important findings set the foundation for additional mechanistic and validation studies using this novel noninvasive and clinically translatable technology for modulating MSC biology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0963689720965478DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7784560PMC
October 2020

3D construct of hydroxyapatite/zinc oxide/palladium nanocomposite scaffold for bone tissue engineering.

J Mater Sci Mater Med 2020 Sep 30;31(10):85. Epub 2020 Sep 30.

Marquette University School of Dentistry, Milwaukee, WI, 53233, USA.

The purpose of this study was to produce and characterize Hydroxyapatite/Zinc Oxide/Palladium (HA/0.05 wt% ZnO/0.1 wt% Pd) nanocomposite scaffolds and study their mechanical and antibacterial properties, biocompatibility and bioactivity. The initial materials were developed using sol-gel and precipitation methods. Scaffolds were characterized using atomic absorption analysis (AA), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM), atomic force microscopy (AFM) and Brunauer-EmmeS-Teller (BET) method. Furthermore, the bioactivity of scaffolds in simulated body fluid (SBF) and the interaction of dental pulp stem cells (DPSCs) with the nanocomposite scaffolds were assessed. Our results showed that the HA/ZnO/Pd (H1), HA/ZnO/Pd coated by 0.125 g chitosan (H2) and HA/ZnO/Pd coated by 0.25 g chitosan (H3) scaffolds possess higher compressive strength and toughness and lower microhardness and density compared to the pure HA (H0) scaffolds. Immersion of samples in SBF showed the deposition of apatite on the surface of the scaffolds. The biocompatibility assay indicated lower cell proliferation on the H1, H2 and H3 in comparison to the H0. The antibacterial results obtained show a significant impact by loading Pd/ZnO on HA in the deactivation of microorganisms in vitro.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10856-020-06409-2DOI Listing
September 2020

Facilitating islet transplantation using a three-step approach with mesenchymal stem cells, encapsulation, and pulsed focused ultrasound.

Stem Cell Res Ther 2020 09 18;11(1):405. Epub 2020 Sep 18.

Department of Radiology, Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, 3155 Porter Drive, Palo Alto, CA, 94304, USA.

Background: The aim of this study was to examine the effect of a three-step approach that utilizes the application of adipose tissue-derived mesenchymal stem cells (AD-MSCs), encapsulation, and pulsed focused ultrasound (pFUS) to help the engraftment and function of transplanted islets.

Methods: In step 1, islets were co-cultured with AD-MSCs to form a coating of AD-MSCs on islets: here, AD-MSCs had a cytoprotective effect on islets; in step 2, islets coated with AD-MSCs were conformally encapsulated in a thin layer of alginate using a co-axial air-flow method: here, the capsule enabled AD-MSCs to be in close proximity to islets; in step 3, encapsulated islets coated with AD-MSCs were treated with pFUS: here, pFUS enhanced the secretion of insulin from islets as well as stimulated the cytoprotective effect of AD-MSCs.

Results: Our approach was shown to prevent islet death and preserve islet functionality in vitro. When 175 syngeneic encapsulated islets coated with AD-MSCs were transplanted beneath the kidney capsule of diabetic mice, and then followed every 3 days with pFUS treatment until day 12 post-transplantation, we saw a significant improvement in islet function with diabetic animals re-establishing glycemic control over the course of our study (i.e., 30 days). In addition, our approach was able to enhance islet engraftment by facilitating their revascularization and reducing inflammation.

Conclusions: This study demonstrates that our clinically translatable three-step approach is able to improve the function and viability of transplanted islets.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13287-020-01897-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7501701PMC
September 2020

Pulsed focused ultrasound enhances the therapeutic effect of mesenchymal stromal cell-derived extracellular vesicles in acute kidney injury.

Stem Cell Res Ther 2020 09 14;11(1):398. Epub 2020 Sep 14.

Interventional Regenerative Medicine and Imaging Laboratory, Department of Radiology, Stanford University, Palo Alto, CA, 94304, USA.

Background: Acute kidney injury (AKI) is characterized by rapid failure of renal function and has no curative therapies. Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) are known to carry therapeutic factors, which have shown promise in regenerative medicine applications, including AKI. However, there remains an unmet need to optimize their therapeutic effect. One potential avenue of optimization lies in pulsed focused ultrasound (pFUS), where tissues-of-interest are treated with sound waves. pFUS has been shown to enhance MSC therapy via increased cell homing, but its effects on cell-free EV therapy remain largely unexplored.

Methods: We combine pFUS pretreatment of the kidney with MSC-derived EV therapy in a mouse model of cisplatin-induced AKI.

Results: EVs significantly improved kidney function, reduced injury markers, mediated increased proliferation, and reduced inflammation and apoptosis. While pFUS did not enhance EV homing to the kidney, the combined treatment resulted in a superior therapeutic effect compared to either treatment alone. We identified several molecular mechanisms underlying this synergistic therapeutic effect, including upregulation of proliferative signaling (MAPK/ERK, PI3K/Akt) and regenerative pathways (eNOS, SIRT3), as well as suppression of inflammation.

Conclusion: Taken together, pFUS may be a strategy for enhancing the therapeutic efficacy of MSC-derived EV treatment for the treatment of AKI.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13287-020-01922-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7490886PMC
September 2020

Controlled Nutrient Delivery to Pancreatic Islets Using Polydopamine-Coated Mesoporous Silica Nanoparticles.

Nano Lett 2020 10 21;20(10):7220-7229. Epub 2020 Sep 21.

Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, Department of Radiology, Palo Alto, California 94304, United States.

In the present study, we created a nanoscale platform that can deliver nutrients to pancreatic islets in a controlled manner. Our platform consists of a mesoporous silica nanoparticle (MSNP), which can be loaded with glutamine (G: an essential amino acid required for islet survival and function). To control the release of G, MSNPs were coated with a polydopamine (PD) layer. With the optimal parameters (0.5 mg/mL and 0.5 h), MSNPs were coated with a layer of PD, which resulted in a delay of G release from MSNPs over 14 d (57.4 ± 4.7% release). Following syngeneic renal subcapsule islet transplantation in diabetic mice, PDG-MSNPs improved the engraftment of islets (i.e., enhanced revascularization and reduced inflammation) as well as their function, resulting in re-establishment of glycemic control. Collectively, our data show that PDG-MSNPs can support transplanted islets by providing them with a controlled and sustained supply of nutrients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.0c02576DOI Listing
October 2020

Meta-Analysis Comparing Watchman and Amplatzer Devices for Stroke Prevention in Atrial Fibrillation.

Front Cardiovasc Med 2020 22;7:89. Epub 2020 Jun 22.

Baylor College of Medicine, Houston, TX, United States.

For patients with atrial fibrillation who are at high risk for bleeding or who cannot tolerate oral anticoagulation, left atrial appendage (LAA) closure represents an alternative therapy for reducing risk for thromboembolic events. To compare the efficacy and safety of the Amplatzer and Watchman LAA closure devices. A meta-analysis was performed of studies comparing the safety and efficacy outcomes of the two devices. The Newcastle-Ottawa Scale was used to appraise study quality. Six studies encompassing 614 patients were included in the meta-analysis. Overall event rates were low for both devices. No significant differences between the devices were found in safety outcomes (i.e., pericardial effusion, cardiac tamponade, device embolization, air embolism, and vascular complications) or in the rates of all-cause mortality, cardiac death, stroke/transient ischemic attack, or device-related thrombosis. The total bleeding rate was significantly lower in the Watchman group (Log OR = -0.90; 95% CI = -1.76 to -0.04; = 0.04), yet no significant differences was found when the bleeding rate was categorized into major and minor bleeding. Total peridevice leakage rate and insignificant peridevice leakage rate were significantly higher in the Watchman group (Log OR = 1.32; 95% CI = 0.76 to 1.87; < 0.01 and Log OR = 1.11; 95% CI = 0.50 to 1.72; < 0.01, respectively). However, significant peridevice leakages were similar in both the devices. The LAA closure devices had low complication rates and low event rates. Efficacy and safety were similar between the systems, except for a higher percentage of insignificant peridevice leakages in the Watchman group. A randomized controlled trial comparing both devices is underway, which may provide more insight on the safety and efficacy outcomes comparison of the devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcvm.2020.00089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322993PMC
June 2020

Contact-force recovery predicts the absence of cardiac perforation during steam pops.

J Interv Card Electrophysiol 2020 Jun 13. Epub 2020 Jun 13.

Center for Cardiac Arrhythmias and Electrophysiology, Texas Heart Institute, 6624 Fannin St, Suite 2470, Houston, TX, 77030, USA.

Purpose: Cardiac perforation (CP) is an uncommon but clinically important complication of radiofrequency ablation (RFA). We previously showed that contact-force recovery after a steam pop predicts the absence of CP in an open-chest animal model after pericardial dissection. We attempted to determine whether this also applies when pericardium is present.

Methods: In 5 open-chest sheep, left atrial RFA was performed under direct observation with a 7.5F ThermoCool SmartTouch force-sensing catheter (Biosense Webster Inc., Irvine, CA, USA). The catheter's contact force was measured every 50 ms during RFA. After each steam pop, the presence (+) or absence (-) of CP was noted, as well as whether pericardium was present over the ablation site. Contact-force signals were analyzed to detect contact-force recovery. Perforation rates were compared between sites with or without pericardium.

Results: Ninety-six steam pops occurred: 77 with pericardium and 19 without. For the pericardial steam pops, contact-force recovery occurred in 31/60 CP- events (52%) and 1/17 CP+ events (6%; P = 0.0006). For nonpericardial steam pops, contact-force recovery occurred in 4/9 CP- events (44%) and 1/10 CP+ events (P = 0.14). The rate of CP was 22% with pericardium and 52% without (P = 0.02). Pericardial tissue charred extensively during steam pop induction, even in the absence of CP.

Conclusions: Contact-force recovery predicts the absence of CP during RFA independently of whether the pericardium is present. The presence of the pericardium may decrease the likelihood of perforation, perhaps by acting as a thermal sink. Additional studies are needed to correlate these results with clinical experience.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10840-020-00794-yDOI Listing
June 2020

Safety and Accuracy of a Novel Bioimpedance System for Real-Time Detection and Monitoring of Endovascular Procedure-Related Bleeding in a Porcine Model.

J Invasive Cardiol 2020 Jul 8;32(7):249-254. Epub 2020 Jun 8.

Gagnon Cardiovascular Institute, Morristown Medical Center, 100 Madison Avenue, Morristown, NJ 07960 USA.

Objectives: The aim of this study was to determine the safety and accuracy of a novel bleed detection system, the Early Bird Bleed Monitoring System (EBBMS; Saranas) for the detection of simulated internal bleeding and the monitoring of bleed progression associated with endovascular procedures.

Background: Periprocedural bleeding events during endovascular procedures are frequent and are associated with increased morbidity, mortality, and healthcare costs.

Methods: This study was a prospective, self-controlled, acute animal study including 20 Yorkshire cross swine undergoing endovascular procedures involving cannulation of both femoral artery and vein. Extravascular bleeding was simulated by a continuous and controlled subcutaneous injection of a blood solution proximal to the access site. The capacity of the EBBMS to detect bleed occurrence and to characterize its progression in three levels of severity (level 1, level 2, level 3) was assessed. Sensitivity and specificity in bleed detection were determined.

Results: Forty EBBMS devices were inserted in 20 animals. During these 40 procedures, bleeding was appropriately detected in all of them. The EBBMS achieved a sensitivity of 100% and specificity of 100% in detection of bleeding. Detection of bleeding progression at level 1 severity occurred at 31.5 ± 12.7 mL, level 2 severity at 77.8 ± 53.5 mL, and level 3 severity at 145.5 ± 100.5 mL, with a significant difference in blood volume (P<.001). No significant difference in bleed detection was seen when the EBBMS was inserted in the femoral vein or artery. CONCLUSION The EBBMS accurately detected access-related bleeding onset and progression during a simulated endovascular procedure.
View Article and Find Full Text PDF

Download full-text PDF

Source
July 2020

First-in-Human Study of the Saranas Early Bird Bleed Monitoring System for the Detection of Endovascular Procedure-Related Bleeding Events.

J Invasive Cardiol 2020 Jul 8;32(7):255-261. Epub 2020 Jun 8.

Gagnon Cardiovascular Institute, Morristown Medical Center, 100 Madison Avenue, Morristown, NJ 07960 USA.

Objectives: To evaluate the safety and accuracy of the Early Bird Bleed Monitoring System (EBBMS; Saranas) for the detection of access-site related bleeds in humans undergoing endovascular procedures.

Background: Bleeding complications after endovascular procedures are frequent and associated with poor prognosis. The EBBMS is a novel technology designed to detect in real time the onset, progression, and severity of internal bleeds.

Methods: The EBBMS was used during and after endovascular procedures, either as a venous or arterial access sheath. The primary endpoint was the level of agreement in bleed detection between the Saranas EBBMS and postprocedural computed tomography.

Results: From August 2018 to December 2018, a total of 60 patients from five United States sites were enrolled and underwent elective endovascular procedures (transcatheter aortic valve replacement [67%], percutaneous coronary intervention [13%], percutaneous ventricular assist device [8%], balloon aortic valvuloplasty [7%], transcatheter mitral valve repair/replacement [4%], and endovascular aneurysmal repair [2%]). The EBBMS detected the absence of bleeds in 21 patients (35%) and bleeds in 39 patients (65%), with bleeding severity level 1 in 20 patients (33%), level 2 in 15 patients (25%), and level 3 in 4 patients (7%). Bleeding detection occurred during the procedure in 31% of patients and post procedure in 69% of patients. The level of agreement between the EBBMS and computed tomography scan was high (Cohen's kappa=0.84). No device-related complications were reported.

Conclusions: The EBBMS was safe across a variety of endovascular procedures and detected bleeding events with a high level of agreement with postprocedural computed tomography scan.
View Article and Find Full Text PDF

Download full-text PDF

Source
July 2020

Confirming pericardial access by using impedance measurements from a micropuncture needle.

Pacing Clin Electrophysiol 2020 06 7;43(6):593-601. Epub 2020 May 7.

Electrophysiology Clinical Research and Innovations, Texas Heart Institute, Houston, Texas.

Background: Pericardial access is complicated by two difficulties: confirming when the needle tip is in the pericardial space, and avoiding complications during access, such as inadvertently puncturing other organs. Conventional imaging tools are inadequate for addressing these difficulties, as they lack soft-tissue markers that could be used as guidance during access. A system that can both confirm access and avoid inadvertent organ injury is needed.

Methods: A 21G micropuncture needle was modified to include two small electrodes at the needle tip. With continuous bioimpedance monitoring from the electrodes, the needle was used to access the pericardium in porcine models (n  =  4). The needle was also visualized in vivo by using an electroanatomical map (n  =  2). Bioimpedance data from different tissues were analyzed retrospectively.

Results: Bioimpedance data collected from the subcutaneous space (992.8 ± 13.1 Ω), anterior mediastinum (972.2 ± 14.2 Ω), pericardial space (323.2 ± 17.1 Ω), mid-myocardium (349.7 ± 87.6 Ω), right ventricular cavity (235.0 ± 9.7 Ω), lung (1142.0 ± 172.0 Ω), liver (575.0 ± 52.6 Ω), and blood (177.5 ± 1.9 Ω) differed significantly by tissue type (P < .01). Phase data in the frequency domain correlated well with the needle being in the pericardial space. A simple threshold analysis effectively separated lung (threshold  =  1120.0 Ω) and blood (threshold  =  305.9 Ω) tissues from the other tissue types.

Conclusions: Continuous bioimpedance monitoring from a modified micropuncture needle during pericardial access can be used to clearly differentiate tissues. Combined with traditional imaging modalities, this system allows for confirming access to the pericardial space while avoiding inadvertent puncture of other organs, creating a safer and more efficient needle-access procedure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pace.13927DOI Listing
June 2020

A Novel Approach to Deliver Therapeutic Extracellular Vesicles Directly into the Mouse Kidney via Its Arterial Blood Supply.

Cells 2020 04 10;9(4). Epub 2020 Apr 10.

Interventional Regenerative Medicine and Imaging Laboratory, Department of Radiology, Stanford University School of Medicine, Palo Alto, CA 94304, USA.

Diseases of the kidney contribute a significant morbidity and mortality burden on society. Localized delivery of therapeutics directly into the kidney, via its arterial blood supply, has the potential to enhance their therapeutic efficacy while limiting side effects associated with conventional systemic delivery. Targeted delivery in humans is feasible given that we can access the renal arterial blood supply using minimally invasive endovascular techniques and imaging guidance. However, there is currently no described way to reproduce or mimic this approach in a small animal model. Here, we develop in mice a reproducible microsurgical technique for the delivery of therapeutics directly into each kidney, via its arterial blood supply. Using our technique, intra-arterially (IA) injected tattoo dye homogenously stained both kidneys, without staining any other organ. Survival studies showed no resulting mortality or iatrogenic kidney injury. We demonstrate the therapeutic potential of our technique in a mouse model of cisplatin-induced acute kidney injury (AKI). IA injection of mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) successfully reversed AKI, with reduced physiological and molecular markers of kidney injury, attenuated inflammation, and restoration of proliferation and regeneration markers. This reproducible delivery technique will allow for further pre-clinical translational studies investigating other therapies for the treatment of renal pathologies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/cells9040937DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7226986PMC
April 2020

Slow-pathway visualization by using voltage-time relationship: A novel technique for identification and fluoroless ablation of atrioventricular nodal reentrant tachycardia.

J Cardiovasc Electrophysiol 2020 06 15;31(6):1430-1435. Epub 2020 Apr 15.

Department of Internal Medicine, Section of Cardiology, Baylor College of Medicine, Houston, Texas.

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) is treatable by catheter ablation. Advances in mapping-system technology permit fluoroless workflow during ablations. As national practice trends toward fluoroless approaches, easily obtained, reproducible methods of slow-pathway identification, and ablation become increasingly important. We present a novel method of slow-pathway identification and initial ablation results from this method.

Methods And Results: We examined AVNRT ablations performed at our institution over a 12-month period. In these cases, the site of the slow pathway was predicted by latest activation in the inferior triangle of Koch during sinus rhythm. Ablation was performed in this region. Proximity of the predicted site to the successful ablation location, complication rates, and patient outcomes were recorded. Junctional rhythm was seen in 40/41 ablations (98%) at the predicted site (mean, 1.3 lesions and median, 1 lesion per case). One lesion was defined as 5 mm of ablation. The initial ablation was successful in 39/41 cases (95%); in two cases, greater or equal to 2 echo beats were detected after the initial ablation, necessitating further lesion expansion. In 8/41 cases (20%), greater than one lesion was placed during initial ablation before attempted reinduction. Complications included one transient heart block and one transient PR prolongation. During follow-up (median, day 51), one patient had lower-extremity deep-vein thrombosis and pulmonary embolus, and one had a lower-extremity superficial venous thrombosis. There was one tachycardia recurrence, which prompted a redo ablation.

Conclusions: Mapping-system detection of late-activation, low-amplitude voltage during sinus rhythm provides an objective, and fluoroless means of identifying the slow pathway in typical AVNRT.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jce.14481DOI Listing
June 2020

Author Correction: Synchronized Biventricular Heart Pacing in a Closed-chest Porcine Model based on Wirelessly Powered Leadless Pacemakers.

Sci Rep 2020 Apr 7;10(1):6252. Epub 2020 Apr 7.

Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-63288-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136257PMC
April 2020

Biodegradable Magnesium Bone Implants Coated with a Novel Bioceramic Nanocomposite.

Materials (Basel) 2020 Mar 13;13(6). Epub 2020 Mar 13.

Electrical and Computer Engineering Department, North Carolina State University, Raleigh, NC 27606, USA.

Magnesium (Mg) alloys are being investigated as a biodegradable metallic biomaterial because of their mechanical property profile, which is similar to the human bone. However, implants based on Mg alloys are corroded quickly in the body before the bone fracture is fully healed. Therefore, we aimed to reduce the corrosion rate of Mg using a double protective layer. We used a magnesium-aluminum-zinc alloy (AZ91) and treated its surface with micro-arc oxidation (MAO) technique to first form an intermediate layer. Next, a bioceramic nanocomposite composed of diopside, bredigite, and fluoridated hydroxyapatite (FHA) was coated on the surface of MAO treated AZ91 using the electrophoretic deposition (EPD) technique. Our in vivo results showed a significant enhancement in the bioactivity of the nanocomposite coated AZ91 implant compared to the uncoated control implant. Implantation of the uncoated AZ91 caused a significant release of hydrogen bubbles around the implant, which was reduced when the nanocomposite coated implants were used. Using histology, this reduction in the corrosion rate of the coated implants resulted in an improved new bone formation and reduced inflammation in the interface of the implants and the surrounding tissue. Hence, our strategy using a MAO/EPD of a bioceramic nanocomposite coating (i.e., diopside-bredigite-FHA) can significantly reduce the corrosion rate and improve the bioactivity of the biodegradable AZ91 Mg implant.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma13061315DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7143302PMC
March 2020

Synchronized Biventricular Heart Pacing in a Closed-chest Porcine Model based on Wirelessly Powered Leadless Pacemakers.

Sci Rep 2020 02 7;10(1):2067. Epub 2020 Feb 7.

Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA.

About 30% of patients with impaired cardiac function have ventricular dyssynchrony and seek cardiac resynchronization therapy (CRT). In this study, we demonstrate synchronized biventricular (BiV) pacing in a leadless fashion by implementing miniaturized and wirelessly powered pacemakers. With their flexible form factors, two pacemakers were implanted epicardially on the right and left ventricles of a porcine model and were inductively powered at 13.56 MHz and 40.68 MHz industrial, scientific, and medical (ISM) bands, respectively. The power consumption of these pacemakers is reduced to µW-level by a novel integrated circuit design, which considerably extends the maximum operating distance. Leadless BiV pacing is demonstrated for the first time in both open-chest and closed-chest porcine settings. The clinical outcomes associated with different interventricular delays are verified through electrophysiologic and hemodynamic responses. The closed-chest pacing only requires the external source power of 0.3 W and 0.8 W at 13.56 MHz and 40.68 MHz, respectively, which leads to specific absorption rates (SARs) 2-3 orders of magnitude lower than the safety regulation limit. This work serves as a basis for future wirelessly powered leadless pacemakers that address various cardiac resynchronization challenges.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-59017-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7005712PMC
February 2020

Effect of Pulsed Focused Ultrasound on the Native Pancreas.

Ultrasound Med Biol 2020 Mar 24;46(3):630-638. Epub 2019 Dec 24.

Interventional Regenerative Medicine and Imaging Laboratory, Department of Radiology, Stanford University School of Medicine, Palo Alto, California 94304, USA. Electronic address:

Pulsed focused ultrasound (pFUS) utilizes short cycles of sound waves to mechanically shake cells within tissues which, in turn, causes transient local increases in cytokines, growth factors and cell adhesion molecules. Although the effect of pFUS has been investigated in several different organs including the kidney, muscle and heart, its effect on the pancreas has not been investigated. In the present work, we applied pFUS to the rodent pancreas with the following parameters: 1.1-MHz frequency, 5-Hz pulse repetition frequency, 5% duty cycle, 10-ms pulse length, 160-s duration. Low-intensity pFUS had a spatial average temporal average intensity of 11.5 W/cm and a negative peak pressure of 3 MPa; high-intensity pFUS had a spatial average temporal average intensity of 18.5 W/cm and negative peak pressure of 4 MPa. Here we found that pFUS changed the expression of several cytokines while having no effect on the underlying tissue histology or health of pancreatic cells (as reflected by no significant change in plasma levels of amylase and lipase). Furthermore, we found that this effect on cytokine expression in the pancreas was acoustic intensity dependent; while pFUS at low intensities turned off the expression of several cytokines, at high intensities it had the opposite effect and turned on the expression of these cytokines. The ability to non-invasively manipulate the microenvironment of the pancreas using sound waves could have profound implications for priming and modulating this organ for the application of cellular therapies in the context of both regenerative medicine (i.e., diabetes and pancreatitis) and oncology (i.e., pancreatic cancer).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ultrasmedbio.2019.11.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010559PMC
March 2020

A Study Comparing the Effects of Targeted Intra-Arterial and Systemic Chemotherapy in an Orthotopic Mouse Model of Pancreatic Cancer.

Sci Rep 2019 11 4;9(1):15929. Epub 2019 Nov 4.

Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, Department of Radiology, Palo Alto, California, 94304, USA.

Systemic chemotherapy is the first line treatment for patients with unresectable pancreatic cancer, however, insufficient drug delivery to the pancreas is a major problem resulting in poor outcomes. We evaluated the therapeutic effects of targeted intra-arterial (IA) delivery of gemcitabine directly into the pancreas in an orthotopic mouse model of pancreatic cancer. Nude mice with orthotopic pancreatic tumors were randomly assigned into 3 groups receiving gemcitabine: systemic intravenous (IV) injection (low: 0.3 mg/kg and high: 100 mg/kg) and direct IA injection (0.3 mg/kg). Treatments were administered weekly for 2 weeks. IA treatment resulted in a significantly greater reduction in tumor growth compared to low IV treatment. To achieve a comparable reduction in tumor growth as seen with IA treatment, gemcitabine had to be given IV at over 300x the dose (high IV treatment) which was associated with some toxicity. After 2 weeks, tumor samples from animals treated with IA gemcitabine had significantly lower residual cancer cells, higher cellular necrosis and evidence of increased apoptosis when compared to animals treated with low IV gemcitabine. Our study shows targeted IA injection of gemcitabine directly into the pancreas, via its arterial blood supply, has a superior therapeutic effect in reducing tumor growth compared to the same concentration administered by conventional systemic injection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-52490-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828954PMC
November 2019

Improving the Function and Engraftment of Transplanted Pancreatic Islets Using Pulsed Focused Ultrasound Therapy.

Sci Rep 2019 09 16;9(1):13416. Epub 2019 Sep 16.

Interventional Regenerative Medicine and Imaging Laboratory, Stanford University School of Medicine, Department of Radiology, Palo Alto, California, 94304, USA.

This study demonstrates that pulsed focused ultrasound (pFUS) therapy can non-invasively enhance the function and engraftment of pancreatic islets following transplantation. In vitro, we show that islets treated with pFUS at low (peak negative pressure (PNP): 106kPa, spatial peak temporal peak intensity (I): 0.71 W/cm), medium (PNP: 150kPa, I: 1.43 W/cm) or high (PNP: 212kPa, I: 2.86 W/cm) acoustic intensities were stimulated resulting in an increase in their function (i.e. insulin secretion at low-intensity: 1.15 ± 0.17, medium-intensity: 2.02 ± 0.25, and high-intensity: 2.54 ± 0.38 fold increase when compared to control untreated islets; P < 0.05). Furthermore, we have shown that this improvement in islet function is a result of pFUS increasing the intracellular concentration of calcium (Ca) within islets which was also linked to pFUS increasing the resting membrane potential (V) of islets. Following syngeneic renal sub-capsule islet transplantation in C57/B6 mice, pFUS (PNP: 2.9 MPa, I: 895 W/cm) improved the function of transplanted islets with diabetic animals rapidly re-establishing glycemic control. In addition, pFUS was able to enhance the engraftment by facilitating islet revascularization and reducing inflammation. Given a significant number of islets are lost immediately following transplantation, pFUS has the potential to be used in humans as a novel non-invasive therapy to facilitate islet function and engraftment, thereby improving the outcome of diabetic patients undergoing islet transplantation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-49933-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746980PMC
September 2019

Imaging Tumor Oxidative Stress with Surface Enhanced Raman Scattering Gold Nanoparticles.

J Biomed Nanotechnol 2019 Oct;15(10):2130-2141

We synthesized a new surface enhanced Raman scattering nanoparticle (SERS NP) which can detect reactive oxygen species (ROS) and thus changes in oxidative stress (OS). Our SERS NP was synthesized using a gold nanoparticle (AuNP) core which was then coated with a dihydrorhodamine (DHR123) Raman layer. In the presence of ROS, DHR123 is converted to rhodamine123 (Rd123) which has a distinct Raman fingerprint. Next, AuNP-DHR123 were encapsulated in a mesoporous-SiO₂ shell to help appose DHR123 to the AuNP core. Finally, the AuNP-DHR123-mesoporous-SiO₂ was functionalized with cystine knot peptides that target integrin . Our SERS NP was initially optimized using solutions containing reactive oxygen species as well as human cancer cell lines. Finally, in a xenograft animal model, we demonstrated the ability of our SERS NP to target a tumor, as well as provide a reading of the amount of OS within the tumor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1166/jbn.2019.2819DOI Listing
October 2019

Three-dimensional cryogels for biomedical applications.

J Biomed Mater Res A 2019 12 27;107(12):2736-2755. Epub 2019 Aug 27.

Interventional Regenerative Medicine and Imaging Laboratory, Department of Radiology, Stanford University, School of Medicine, Palo Alto, California.

Cryogels are a subset of hydrogels synthesized under sub-zero temperatures: initially solvents undergo active freezing, which causes crystal formation, which is then followed by active melting to create interconnected supermacropores. Cryogels possess several attributes suited for their use as bioscaffolds, including physical resilience, bio-adaptability, and a macroporous architecture. Furthermore, their structure facilitates cellular migration, tissue-ingrowth, and diffusion of solutes, including nano- and micro-particle trafficking, into its supermacropores. Currently, subsets of cryogels made from both natural biopolymers such as gelatin, collagen, laminin, chitosan, silk fibroin, and agarose and/or synthetic biopolymers such as hydroxyethyl methacrylate, poly-vinyl alcohol, and poly(ethylene glycol) have been employed as 3D bioscaffolds. These cryogels have been used for different applications such as cartilage, bone, muscle, nerve, cardiovascular, and lung regeneration. Cryogels have also been used in wound healing, stem cell therapy, and diabetes cellular therapy. In this review, we summarize the synthesis protocol and properties of cryogels, evaluation techniques as well as current in vitro and in vivo cryogel applications. A discussion of the potential benefit of cryogels for future research and their application are also presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jbm.a.36777DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7929089PMC
December 2019

In Vivo Restoration of Myocardial Conduction With Carbon Nanotube Fibers.

Circ Arrhythm Electrophysiol 2019 08 12;12(8):e007256. Epub 2019 Aug 12.

Departments of Chemical and Biomolecular Engineering, Chemistry, and Materials Science and NanoEngineering, The Smalley-Curl Institute, Rice University, Houston, TX (F.V., J.S.Y., C.C.Y., J.A.C., M.P.).

Background: Impaired myocardial conduction is the underlying mechanism for re-entrant arrhythmias. Carbon nanotube fibers (CNTfs) combine the mechanical properties of suture materials with the conductive properties of metals and may form a restorative solution to impaired myocardial conduction.

Methods: Acute open chest electrophysiology studies were performed in sheep (n=3). Radiofrequency ablation was used to create epicardial conduction delay after which CNTf and then silk suture controls were applied. CNTfs were surgically sewn across the right atrioventricular junction in rodents, and acute (n=3) and chronic (4-week, n=6) electrophysiology studies were performed. Rodent toxicity studies (n=10) were performed. Electrical analysis of the CNTf-myocardial interface was performed.

Results: In all cases, the large animal studies demonstrated improvement in conduction velocity using CNTf. The acute rodent model demonstrated ventricular preexcitation during sinus rhythm. All chronic cases demonstrated resumption of atrioventricular conduction, but these required atrial pacing. There was no gross or histopathologic evidence of toxicity. Ex vivo studies demonstrated contact impedance significantly lower than platinum iridium.

Conclusions: Here, we show that in sheep, CNTfs sewn across epicardial scar acutely improve conduction. In addition, CNTf maintain conduction for 1 month after atrioventricular nodal ablation in the absence of inflammatory or toxic responses in rats but only in the paced condition. The CNTf/myocardial interface has such low impedance that CNTf can facilitate local, downstream myocardial activation. CNTf are conductive, biocompatible materials that restore electrical conduction in diseased myocardium, offering potential long-term restorative solutions in pathologies interrupting efficient electrical transduction in electrically excitable tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCEP.119.007256DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6858663PMC
August 2019

Assessment of magnesium-based biomaterials: from bench to clinic.

Biomater Sci 2019 May;7(6):2241-2263

Brunel Center for Advanced Solidification Technology (BCAST), Institute of Materials and Manufacturing, Brunel University London, Uxbridge, London UB8 3PH, UK.

Despite the high potential of biodegradable magnesium (Mg) alloys as a new generation of biomaterials for orthopaedic and cardiovascular implantation, their high corrosion rate in body fluid limits their suitability for clinical applications. Extensive research has been performed to improve the corrosion resistance of Mg-based biomaterials. Researchers have also been working to develop new testing and assessment techniques to evaluate the corrosion performance and other in vitro and in vivo properties of their modified Mg alloys. The objective of this review is to present the principles and operation procedures of commonly used standard methods for assessment of Mg-based biomaterials from bench to clinic. The pros and cons of each of these methods are discussed, together with factors for consideration to choose the right methodology. This review also presents the current state and challenges in understanding the testing of Mg-based biomaterials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9bm00289hDOI Listing
May 2019