Publications by authors named "May P Xiong"

27 Publications

  • Page 1 of 1

Synthesis and evaluation of an amphiphilic deferoxamine:gallium-conjugated cationic random copolymer against a murine wound healing infection model of Pseudomonas aeruginosa.

Acta Biomater 2021 05 8;126:384-393. Epub 2021 Mar 8.

Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602-2352, United States. Electronic address:

Multidrug resistant (MDR) Gram-negative bacteria are an urgent global health threat. We report on the design and evaluation of a xenosiderophore-conjugated cationic random copolymer (pGQ-DG) which exhibits selective antibacterial activity against Pseudomonas aeruginosa (P. aeruginosa) by targeting select outer membrane (OM) receptors for scavenging xenosiderophores such as deferoxamine (DFO), while possessing favorable cytocompatibility and exhibiting low hemolysis, to enhance and safely damage the bacterial OM. pGQ-DG demonstrated synergistic properties in combination with vancomycin (VAN) when evaluated in vitro against P. aeruginosa. In addition, pGQ-DG plus VAN cleared the P. aeruginosa infection and efficiently accelerated healing in a murine wound healing model as effectively as colistin, suggesting that this strategy could serve as an alternative to colistin against MDR bacteria. STATEMENT OF SIGNIFICANCE: P. aeruginosa exhibits intrinsic antibiotic resistance due to limited permeability of its outer membrane (OM). A triple combination antipseudomonal approach was investigated by 1) selectively targeting P. aeruginosa through the complex DFO:gallium, 2) disrupting the OM through a cationic random copolymer, and 3) enhancing bacteria sensitivity to VAN as a result of the OM disruption. Synthesis and characterization of the lead polymer pGQ-DG, mechanism of action, antimicrobial activity, and biocompatibility were investigated in vitro and in vivo. Overall pGQ-DG plus VAN cleared the P. aeruginosa infection and accelerated wound healing in mice as effectively as colistin, suggesting that this strategy could serve as an alternative to colistin against multidrug resistant P. aeruginosa.
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http://dx.doi.org/10.1016/j.actbio.2021.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8096703PMC
May 2021

Reactive Oxygen Species-Triggered Dissociation of a Polyrotaxane-Based Nanochelator for Enhanced Clearance of Systemic and Hepatic Iron.

ACS Nano 2021 01 30;15(1):419-433. Epub 2020 Dec 30.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, Georgia 30602, United States.

Chronic blood transfusions are used to alleviate anemic symptoms in thalassemia and sickle cell anemia patients but can eventually result in iron overload (IO) and subsequently lead to severe oxidative stress in cells and tissues. Deferoxamine (DFO) is clinically approved to treat transfusional IO, but the use of the iron chelator is hindered by nonspecific toxicity and poor pharmacokinetic (PK) properties in humans, resulting in the need to administer the drug long-term infusion regimens that can often lead to poor patient compliance. Herein, a nanochelator system that uses the characteristic IO physiological environment to dissociate was prepared through the incorporation of DFO and reactive oxygen species (ROS)-sensitive thioketal groups into an α-cyclodextrin-based polyrotaxane platform (rPR-DFO). ROS-induced dissociation of this nanochelator (. 10 nm) into constructs averaging 2 nm in diameter significantly increased urine and fecal elimination of excess iron . In addition to significantly improved PK properties, rPR-DFO was well-tolerated in mice and no adverse side effects were noted in single high dose or multiple dose acute toxicity studies. The overall features of rPR-DFO as a promising system for iron chelation therapy can be attributed to a combination of the nanochelator's improved PK, favorable distribution to the liver, and ROS-induced dissociation properties into constructs <6 nm for faster renal elimination. This ROS-responsive nanochelator design may serve as a promising alternative for safely prolonging the circulation of DFO and more rapidly eliminating iron chelates from the body in iron chelation therapy regimens requiring repeated dosing of nanochelators.
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http://dx.doi.org/10.1021/acsnano.0c01083DOI Listing
January 2021

Effects of Polyethyelene Glycol-Desferrioxamine:Gallium Conjugates on Outer Membrane Permeability and Vancomycin Potentiation.

Mol Pharm 2021 02 4;18(2):735-742. Epub 2020 Nov 4.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, Georgia 30602, United States.

exhibits a broad spectrum of intrinsic antibiotic resistance because of the limited permeability of its outer membrane. Given this situation, molecules that could make Gram-negative bacteria more permeable and more susceptible to large-scaffold Gram-positive antibiotics may be advantageous. Herein, we evaluate the antimicrobial activity of a series of targeted poly(ethylene glycol)-desferrioxamine/gallium (PEG-DG) conjugates that can improve the sensitivity of to the glycopeptide vancomycin (VAN). We observed that single-ended mPEG-DG and double-ended PEG-DG conjugates characterized by PEG MW ≥2000 synergistically enhanced the sensitivity of VAN against reference strains PAO1 and ATCC 27853 and three clinically isolated carbapenem-resistant strains, but not strain ATCC 25922. Although the exact mechanism of this phenomenon is currently under investigation, PEG-DG conjugates enhanced nitrocefin (NCF), hexidium iodide (HI), and VAN permeability only when PEG and DG were directly conjugated. The two most important physicochemical factors contributing to the synergistic activity observed with VAN relate to (1) the final concentration of DG ligands conjugated to the polymer and (2) the polymer length, wherein MW ≥2000 yielded a similar fractional inhibitory concentration.
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http://dx.doi.org/10.1021/acs.molpharmaceut.0c00820DOI Listing
February 2021

Challenges and Opportunities of Deferoxamine Delivery for Treatment of Alzheimer's Disease, Parkinson's Disease, and Intracerebral Hemorrhage.

Mol Pharm 2021 02 9;18(2):593-609. Epub 2020 Oct 9.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, Georgia 30602, United States.

Deferoxamine mesylate (DFO) is an FDA-approved, hexadentate iron chelator routinely used to alleviate systemic iron burden in thalassemia major and sickle cell patients. Iron accumulation in these disease states results from the repeated blood transfusions required to manage these conditions. Iron accumulation has also been implicated in the pathogenesis of Alzheimer's disease (AD), Parkinson's disease (PD), and secondary injury following intracerebral hemorrhage (ICH). Chelation of brain iron is thus a promising therapeutic strategy for improving behavioral outcomes and slowing neurodegeneration in the aforementioned disease states, though the effectiveness of DFO treatment is limited on several accounts. Systemically administered DFO results in nonspecific toxicity at high doses, and the drug's short half-life leads to low patient compliance. Mixed reports of DFO's ability to cross the blood-brain barrier (BBB) also appear in literature. These limitations necessitate novel DFO formulations prior to the drug's widespread use in managing neurodegeneration. Herein, we discuss the various dosing regimens and formulations employed in intranasal (IN) or systemic DFO treatment, as well as the physiological and behavioral outcomes observed in animal models of AD, PD, and ICH. The clinical progress of chelation therapy with DFO in managing neurodegeneration is also evaluated. Finally, the elimination of intranasally administered particles via the glymphatic system and efflux transporters is discussed. Abundant preclinical evidence suggests that intranasal DFO treatment improves memory retention and behavioral outcome in rodent models of AD, PD, and ICH. Several other biochemical and physiological metrics, such as tau phosphorylation, the survival of tyrosine hydroxylase-positive neurons, and infarct volume, are also positively affected by intranasal DFO treatment. However, dosing regimens are inconsistent across studies, and little is known about brain DFO concentration following treatment. Systemic DFO treatment yields similar results, and some complex formulations have been developed to improve permeability across the BBB. However, despite the success in preclinical models, clinical translation is limited with most clinical evidence investigating DFO treatment in ICH patients, where high-dose treatment has proven dangerous and dosing regimens are not consistent across studies. DFO is a strong drug candidate for managing neurodegeneration in the aging population, but before it can be routinely implemented as a therapeutic agent, dosing regimens must be standardized, and brain DFO content following drug administration must be understood and controlled via novel formulations.
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http://dx.doi.org/10.1021/acs.molpharmaceut.0c00474DOI Listing
February 2021

Desferrioxamine:gallium-pluronic micelles increase outer membrane permeability and potentiate antibiotic activity against Pseudomonas aeruginosa.

Chem Commun (Camb) 2018 Dec;54(99):13929-13932

Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA, USA.

The outer membrane of Pseudomonas aeruginosa functions primarily as a permeability barrier and imparts a broad spectrum of intrinsic antibiotic resistance. Herein, we describe the synthesis, characterization, and antimicrobial evaluation of a targeted polymeric micelle that specifically permeabilizes the outer membrane and potentiates antibiotic activity against P. aeruginosa.
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http://dx.doi.org/10.1039/c8cc08134dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345168PMC
December 2018

Antibacterial and Potentiation Properties of Charge-Optimized Polyrotaxanes for Combating Opportunistic Bacteria.

J Mater Chem B 2018 Sep 31;6(33):5353-5361. Epub 2018 Jul 31.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602-2352, USA.

Bacteria are now becoming more resistant to most conventional antibiotics. Approaches for the treatment of multidrug-resistant bacterial infections are urgently required. Cationic polymers have broad-spectrum antibacterial activity but can also induce non-specific damage to mammalian cells. Herein, we report on the design of cationic polyrotaxanes (cPRs) with variable charge densities. cPRs were prepared by conjugating neutral ethanolamine and cationic ethylenediamine at various ratios onto threaded alpha-cyclodextrins and their antimicrobial and cytocompatible properties were investigated in vitro. In contact with Gram-negative bacteria, cPRs can disrupt the bacterial outer membrane integrity via electrostatic interactions and penetrate into the cytosol. The ability of cPRs to serve as potentiators at sub-MIC concentrations, to enhance the permeability and activity of poorly permeable antibiotics such as vancomycin, erythromycin and rifampicin, was also investigated against Gram-negative PAO1 and ATCC 25922.
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http://dx.doi.org/10.1039/C8TB01610KDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6205756PMC
September 2018

Terpyridine-Micelles for Inhibiting Bacterial Biofilm Development.

ACS Infect Dis 2018 09 31;4(9):1346-1354. Epub 2018 Jul 31.

Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy , University of Georgia , 250 W. Green Street , Athens , Georgia 30602-2352 , United States.

Iron plays a critical role in bacterial infections and is especially critical for supporting biofilm formation. Until recently, Fe(III) was assumed to be the most relevant form of iron to chelate in therapeutic antimicrobial strategies due to its natural abundance under normal oxygen and physiologic conditions. Recent clinical data obtained from cystic fibrosis (CF) patients found that there is actually quite an abundance of Fe(II) present in sputum and that there exists a significant relationship between sputum Fe(II) concentration and severity of the disease. A biocompatible mixed micelle formed from the self-assembly of poly(lactic- co-glycolic acid)- block-methoxy poly(ethylene glycol) (PLGA- b-mPEG) and poly(lactic- co-glycolic acid)- block-poly(terpyridine) [PLGA- b-p(Tpy)] polymers was prepared to chelate Fe(II) (Tpy-micelle). Tpy-micelles showed high selectivity for Fe(II) over Fe(III), decreased biofilm mass more effectively under anaerobic conditions at >4 μM Tpy-micelles, reduced bacteria growth in biofilms by >99.9% at 128 μM Tpy-micelles, effectively penetrated throughout a 1-day old biofilm, and inhibited biofilm development in a concentration-dependent manner. This study reveals that Fe(II) chelating Tpy-micelles are a promising addition to Fe(III) chelating strategies to inhibit biofilm formation in CF lung infections.
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http://dx.doi.org/10.1021/acsinfecdis.8b00091DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6138535PMC
September 2018

ROS-triggered degradable iron-chelating nanogels: Safely improving iron elimination in vivo.

J Control Release 2018 08 22;283:84-93. Epub 2018 May 22.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602-2352, USA. Electronic address:

Iron-mediated generation of highly toxic Reactive Oxygen Species (ROS) plays a major role in the process leading to iron overload-related diseases. The long-term subcutaneous administration of Deferoxamine (DFO) is currently clinically-approved to improve patient symptoms and survival. However, non-specific toxicity and short circulation times of the drug in humans often leads to poor patient compliance. Herein, thioketal-based ROS-responsive polymeric nanogels containing DFO moieties (rNG-DFO) were designed to chelate iron and to degrade under oxidative stimuli into fragments <10 nm to enhance excretion of iron-bound chelates. Serum ferritin levels and iron concentrations in major organs of IO mice decreased following treatment with rNG-DFO, and fecal elimination of iron-bound chelates increased compared to free DFO. Furthermore, rNG-DFO decreased iron mediated oxidative stress levels in vitro and reduced iron-mediated inflammation in the liver of IO mice. The study confirms that ROS-responsive nanogels may serve as a promising alternative to DFO for safer and more efficient iron chelation therapy.
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http://dx.doi.org/10.1016/j.jconrel.2018.05.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035766PMC
August 2018

A bioorthogonal turn-on fluorescent strategy for the detection of lysine acetyltransferase activity.

Chem Commun (Camb) 2018 May;54(44):5594-5597

Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, Georgia 30602, USA.

Lysine acetylation plays vital roles in the regulation of fundamental cellular processes, which is mediated by lysine acetyltransferases (KATs). Developing chemical biology probes for KAT activity detection is of important value in providing improved understanding of their biological functions. We reported a panel of "turn-on" fluorescent probes for sensitive and selective detection of KAT enzymatic activity through a simple mix-and-read format. Combined with bioorthogonal substrate labelling and click chemistry, these probes produced strong "turn-on" fluorescent signals in response to KAT-mediated acylation process. This chemical biology strategy diversifies the assay toolboxes to investigate functions and mechanisms of acetyltransferase enzymes.
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http://dx.doi.org/10.1039/c8cc02987cDOI Listing
May 2018

Nanogel-DFO conjugates as a model to investigate pharmacokinetics, biodistribution, and iron chelation in vivo.

Int J Pharm 2018 Mar 16;538(1-2):79-86. Epub 2018 Jan 16.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, USA. Electronic address:

Deferoxamine (DFO) to treat iron overload (IO) has been limited by toxicity issues and short circulation times and it would be desirable to prolong circulation to improve non-transferrin bound iron (NTBI) chelation. In addition, DFO is currently unable to efficiently target the large pool of iron in the liver and spleen. Nanogel-Deferoxamine conjugates (NG-DFO) can prove useful as a model to investigate the pharmacokinetic (PK) properties and biodistribution (BD) behavior of iron-chelating macromolecules and their overall effect on serum ferritin levels. NG-DFO reduced the cytotoxicity of DFO and significantly reduced cellular ferritin levels in IO macrophages in vitro. PK/BD studies in normal rats revealed that NG-DFO displayed prolonged circulation and preferential accumulation into the liver and spleen. IO mice treated with NG1-DFO presented significantly lower levels of serum ferritin compared to DFO. Total renal and fecal elimination data point to the need to balance prolonged circulation with controlled degradation to accelerate clearance of iron-chelating macromolecules.
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http://dx.doi.org/10.1016/j.ijpharm.2018.01.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5845769PMC
March 2018

Multifunctional Polymeric Micelles for Combining Chelation and Detection of Iron in Living Cells.

Adv Healthc Mater 2017 Sep 29;6(17). Epub 2017 Jun 29.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA, 30602-2352, USA.

Multifunctional self-assembled micelles composed of Pluronics F127 polymer chains are developed and investigated for chelation and selective detection of iron(III) in vitro and in iron-overloaded cells. Tetraphenylethene (TPE) is encapsulated into the micelle core and the iron chelate drug deferoxamine (DFO) is conjugated to micelles to generate a fluorescence quenching detection system termed DFO-TFM for short, where T stands for TPE, F for F127, and M for micelle. The key to the successful formation of this fluorescence quenching system is due to the near-ideal overlap between the absorption spectrum of the DFO:iron(III) complex and fluorescence spectrum of TPE. DFO-TFM can retain the iron-chelation properties of DFO and exhibits negligible cytotoxicity compared to free DFO. Furthermore, this fluorescence "turn-off" system can be utilized to detect the presence of iron and to monitor the chelation process in an iron overload cell model. This study serves as an effective proof-of-concept model for designing future in vivo systems capable of combining the features of iron chelation with iron detection and efforts toward the development of such detection systems are currently underway.
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http://dx.doi.org/10.1002/adhm.201700162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5587393PMC
September 2017

Enzymatically Biodegradable Polyrotaxane-Deferoxamine Conjugates for Iron Chelation.

ACS Appl Mater Interfaces 2016 Oct 26;8(39):25788-25797. Epub 2016 Sep 26.

Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, University of Georgia , Athens, Georgia 30602-2352, United States.

Chelation therapy is frequently used to help reduce excess iron in the body, but current chelators such as deferoxamine (DFO) are plagued by short blood circulation times, which necessitates infusions and can cause undesirable toxic side effects in patients. To address these issues, polyrotaxanes (PR) were synthesized by threading α-cyclodextrin (α-CD) onto poly(ethylene glycol) bis(amine) (PEG-BA, MW 3400 g/mol) capped with enzymatically cleavable bulky Z-L phenylalanine (Z-L Phe) moieties. The resulting PR was conjugated to DFO and hydroxypropylated to generate the final polyrotaxane-DFO (hPR-DFO). The iron chelating capability of hPR-DFO was verified by UV-vis absorption spectroscopy and the ability of materials to degrade into smaller CD-conjugated DFO fragments (hCD-DFO) in the presence of the protease was confirmed via gel permeation chromatography. In vitro studies in iron-overloaded macrophages reveal that hPR-DFO can significantly reduce the cytotoxicity of the drug while maintaining its chelation efficacy, and that it is more rapidly endocytosed and trafficked to lysosomes of iron-overloaded cells in comparison to non-iron-overloaded macrophages. In vivo studies indicate that iron-overloaded mice treated with hPR-DFO displayed lower serum ferritin levels (a measure of iron burden in the body) and could eliminate excess iron by both the renal and fecal routes. Moreover, there was no gross evidence of acute toxicological damage to the liver or spleen.
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http://dx.doi.org/10.1021/acsami.6b09077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5560162PMC
October 2016

Modulation of oxidative stress and subsequent induction of apoptosis and endoplasmic reticulum stress allows citral to decrease cancer cell proliferation.

Sci Rep 2016 06 8;6:27530. Epub 2016 Jun 8.

Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI-53792-6188, USA.

The monoterpenoid, citral, when delivered through PEG-b-PCL nanoparticles inhibits in vivo growth of 4T1 breast tumors. Here, we show that citral inhibits proliferation of multiple human cancer cell lines. In p53 expressing ECC-1 and OVCAR-3 but not in p53-deficient SKOV-3 cells, citral induces G1/S cell cycle arrest and apoptosis as determined by Annexin V staining and increased cleaved caspase3 and Bax and decreased Bcl-2. In SKOV-3 cells, citral induces the ER stress markers CHOP, GADD45, EDEM, ATF4, Hsp90, ATG5, and phospho-eIF2α. The molecular chaperone 4-phenylbutyric acid attenuates citral activity in SKOV-3 but not in ECC-1 and OVCAR-3 cells. In p53-expressing cells, citral increases phosphorylation of serine-15 of p53. Activation of p53 increases Bax, PUMA, and NOXA expression. Inhibition of p53 by pifithrin-α, attenuates citral-mediated apoptosis. Citral increases intracellular oxygen radicals and this leads to activation of p53. Inhibition of glutathione synthesis by L-buthionine sulfoxamine increases potency of citral. Pretreatment with N-acetylcysteine decreases phosphorylation of p53 in citral-treated ECC-1 and OVCAR-3. These results define a p53-dependent, and in the absence of p53, ER stress-dependent mode of action of citral. This study indicates that citral in PEG-b-PCL nanoparticle formulation should be considered for treatment of breast and other tumors.
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http://dx.doi.org/10.1038/srep27530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4897611PMC
June 2016

Oxidation-Induced Degradable Nanogels for Iron Chelation.

Sci Rep 2016 Feb 12;6:20923. Epub 2016 Feb 12.

Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison 777 Highland Avenue, Madison, WI 53705-2222, USA.

Iron overload can increase cellular oxidative stress levels due to formation of reactive oxygen species (ROS); untreated, it can be extremely destructive to organs and fatal to patients. Since elevated oxidative stress levels are inherent to the condition in such patients, oxidation-induced degradable nanogels for iron chelation were rationally designed by simultaneously polymerizing oxidation-sensitive host-guest crosslinkers between β-cyclodextrin (β-CD) and ferrocene (Fc) and iron chelating moieties composed of deferoxamine (DFO) into the final gel scaffold in reverse emulsion reaction chambers. UV-Vis absorption and atomic absorption spectroscopy (AAS) was used to verify iron chelating capability of nanogels. These materials can degrade into smaller chelating fragments at rates proportional to the level of oxidative stress present. Conjugating DFO reduces the cytotoxicity of the chelator in the macrophage cells. Importantly, the nanogel can effectively reduce cellular ferritin expression in iron overloaded cells and regulate intracellular iron levels at the same time, which is important for maintaining a homeostatic level of this critical metal in cells.
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http://dx.doi.org/10.1038/srep20923DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4751432PMC
February 2016

Formulation, Characterization, and Antitumor Properties of Trans- and Cis-Citral in the 4T1 Breast Cancer Xenograft Mouse Model.

Pharm Res 2015 Aug 12;32(8):2548-58. Epub 2015 Feb 12.

School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, 53705-2222, USA.

Purpose: Citral is composed of a random mixture of two geometric stereoisomers geranial (trans-citral) and neral (cis-citral) yet few studies have directly compared their in vivo antitumor properties. A micelle formulation was therefore developed.

Methods: Geranial and neral were synthesized. Commercially-purchased citral, geranial, and neral were formulated in PEG-b-PCL (block sizes of 5000:10,000, Mw/Mn 1.26) micelles. In vitro degradation, drug release, cytotoxicity, flow cytometry, and western blot studies were conducted. The antitumor properties of drug formulations (40 and 80 mg/kg based on MTD studies) were evaluated on the 4T1 xenograft mouse model and tumor tissues were analyzed by western blot.

Results: Micelles encapsulated drugs with >50% LE at 5-40% drug to polymer (w/w), displayed sustained release (t1/2 of 8-9 h), and improved drug stability at pH 5.0. The IC50 of drug formulations against 4T1 cells ranged from 1.4 to 9.9 μM. Western blot revealed that autophagy was the main cause of cytotoxicity. Geranial at 80 mg/kg was most effective at inhibiting tumor growth.

Conclusions: Geranial is significantly more potent than neral and citral at 80 mg/kg (p < 0.001) and western blot of tumor tissues confirms that autophagy and not apoptosis is the major mechanism of tumor growth inhibition in p53-null 4T1 cells.
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http://dx.doi.org/10.1007/s11095-015-1643-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4490114PMC
August 2015

Evaluating the anticancer properties of liposomal copper in a nude xenograft mouse model of human prostate cancer: formulation, in vitro, in vivo, histology and tissue distribution studies.

Pharm Res 2014 Nov 22;31(11):3106-19. Epub 2014 May 22.

School of Pharmacy, University of Wisconsin - Madison, Madison, WI, 53705-2222, United State of America.

Purpose: Although Cu complexes have been investigated as anticancer agents, there has been no description of Cu itself as a cancer killing agent. A stealth liposomal Cu formulation (LpCu) was studied in vitro and in vivo.

Methods: LpCu was evaluated in prostate cancer origin PC-3 cells by a metabolic cytotoxicity assay, by monitoring ROS, and by flow cytometry. LpCu efficacy was evaluated in vivo using intratumoral and intravenous injections into mice bearing PC-3 xenograft tumors. Toxicology was assessed by performing hematological and blood biochemistry assays, and tissue histology and Cu distribution was investigated by elemental analysis.

Results: LpCu and free Cu salts displayed similar levels of cell metabolic toxicity and ROS. Flow cytometry indicated that the mechanisms of cell death were both apoptosis and necrosis. Animals injected i.t. with 3.5 mg/kg or i.v. with 3.5 and 7.0 mg/kg LpCu exhibited significant tumor growth inhibition. Kidney and eye were the main organs affected by Cu-mediated toxicities, but spleen and liver were the major organs of Cu deposition.

Conclusions: LpCu was effective at reducing tumor burden in the xenograft prostate cancer model. There was histological evidence of Cu toxicity in kidneys and eyes of animals treated at the maximum tolerated dose of LpCu 7.0 mg/kg.
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http://dx.doi.org/10.1007/s11095-014-1403-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4214917PMC
November 2014

Active drug encapsulation and release kinetics from hydrogel-in-liposome nanoparticles.

J Colloid Interface Sci 2013 Sep 13;406:247-55. Epub 2013 Jun 13.

Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705-2222, USA.

Herein, we demonstrate for the first time the use of hydrogel-in-liposome nanoparticles (lipogels) as a promising drug delivery vehicle for the active encapsulation of the anticancer drug 17-DMAPG, a geldanamycin (GA) derivative. This model drug was chosen due to its improved aqueous solubility (4.6 mg/ml) compared to the parent GA (<0.01 mg/ml), and presence of a tertiary amine which readily protonates at low pH. For the design of lipogels, a PAA hydrogel core was formed inside liposomes through UV-initiated DEAP activation and polymerization of AA and BA. We have demonstrated here that electrostatic interactions between drug and gel are critical for active encapsulation and sustained release of 17-DMAPG. We found that optimal loading conditions could be obtained (88% loading efficiency) through control of pH, temperature and incubation time. Dramatic sustained drug release from lipogels was achieved independent of the external solution pH (ca. 54 h to 50% drug release) and confirmed that the lipid bilayer was intact in the presence of the gel core. In vitro cell culture studies revealed that at the highest concentration tested, which corresponded to approximately 0.4 mg/ml of material, lipogels did not exert cytotoxicity to cells.
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http://dx.doi.org/10.1016/j.jcis.2013.05.081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3717358PMC
September 2013

Trilayer micelles for combination delivery of rapamycin and siRNA targeting Y-box binding protein-1 (siYB-1).

Biomaterials 2013 Sep 12;34(28):6882-92. Epub 2013 Jun 12.

Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705-2222, USA.

A three layer (trilayer) polymeric micelle system based on the self-association of the triblock polymer poly(ethylene glycol)-b-poly{N-[N-(2-aminoethyl)-2-aminoethyl] aspartamide}-b-poly(ε-caprolactone) (PEG-b-PAsp(DET)-b-PCL) has been synthesized and investigated for combination delivery of rapamycin (RAP) and siRNA targeting Y-box binding protein-1 (siYB-1). The trilayer micelle is composed of (a) a hydrophilic poly(ethylene glycol) (PEG) block constituting the outer layer to improve pharmacokinetics, (b) an intermediate compartment composed of the cationic poly{2-[(2-aminoethyl)amino] ethyl aspartamide} (PAsp(DET)) segment for interacting with siYB-1, and (c) an inner hydrophobic poly(ε-caprolactone) (PCL) compartment for encapsulation of RAP. A major advantage of this system is biocompatibility since PEG and PCL are both approved by the FDA, and PAsp(DET) is a non-toxic pH responsive cationic poly(amino acid)-based polymer. In this study, it has been shown that PCL can encapsulate RAP with high loading efficiencies, and PAsp(DET) can successfully interact with siRNA for efficient transfection/knockdown with negligible cytotoxicity. The enhanced therapeutic efficacy of RAP/siYB-1 micelles was demonstrated in cell cultures and in a PC3 xenograft nude mouse model of human prostate cancer. Herein, we demonstrate that trilayer micelles are a promising approach to improve the simultaneous delivery of combination siRNA/drug therapies.
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http://dx.doi.org/10.1016/j.biomaterials.2013.05.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3816790PMC
September 2013

Non-cell-autonomous RNA interference in mammalian cells: Implications for in vivo cell-based RNAi delivery.

J RNAi Gene Silencing 2011 1;7:456-63. Epub 2011 Dec 1.

Pharmaceutical Sciences Division, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA.

RNA interference (RNAi) is a post-transcriptional pathway in which double-stranded RNA (dsRNA) triggers the degradation of complementary mRNA in the cytoplasm of eukaryotic cells. In plants and in some animals, including Caenorhabditis elegans, initiation of RNAi in one cell can lead to sequence-specific RNA silencing in another cell, a phenomenon referred to as non-cell-autonomous RNAi. Until recently, this phenomenon had not been observed in mammalian cells. Here, we review emerging data demonstrating that non-cell-autonomous RNAi occurs in cultured mammalian cells. We discuss possible mechanisms for the transfer of RNAi between mammalian cells and highlight the implications of this phenomenon for the development of in vivo cell-based RNAi delivery.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3244743PMC
October 2012

First natural analogs of the cytotoxic thiodepsipeptide thiocoraline A from a marine Verrucosispora sp.

J Org Chem 2011 Aug 20;76(16):6542-7. Epub 2011 Jul 20.

Division of Pharmaceutical Sciences, University of Wisconsin-Madison, 777 Highland Avenue, Madison, Wisconsin 53705, USA.

A marine Verrucosispora sp. isolated from the sponge Chondrilla caribensis f. caribensis was found to produce thiocoraline, a potent cytotoxic compound. Five new analogs of thiocoraline were isolated and represent the first analogs of thiocoraline. 22'-Deoxythiocoraline (2), thiochondrilline C (5), and 12'-sulfoxythiocoraline (6) demonstrated significant cytotoxicity against the A549 human cancer cell line with EC(50) values of 0.13, 2.86, and 1.26 μM, respectively. The analogs provide insight into the SAR and biosynthesis of thiocoraline. The DP4 probability method was used to analyze ab initio NMR calculations to confirm stereochemical assignments.
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http://dx.doi.org/10.1021/jo200661nDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155634PMC
August 2011

A cremophor-free formulation for tanespimycin (17-AAG) using PEO-b-PDLLA micelles: characterization and pharmacokinetics in rats.

J Pharm Sci 2009 Apr;98(4):1577-86

Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, Kansas 66047-3729, USA.

Tanespimycin (17-allylamino-17-demethoxygeldanamycin or 17-AAG) is a promising heat shock protein 90 inhibitor currently undergoing clinical trials for the treatment of cancer. Despite its selective mechanism of action on cancer cells, 17-AAG faces challenging issues due to its poor aqueous solubility, requiring formulation with Cremophor EL (CrEL) or ethanol (EtOH). Therefore, a CrEL-free formulation of 17-AAG was prepared using amphiphilic diblock micelles of poly(ethylene oxide)-b-poly(D,L-lactide) (PEO-b-PDLLA). Dynamic light scattering revealed PEO-b-PDLLA (12:6 kDa) micelles with average sizes of 257 nm and critical micelle concentrations of 350 nM, solubilizing up to 1.5 mg/mL of 17-AAG. The area under the curve (AUC) of PEO-b-PDLLA micelles was 1.3-fold that of the standard formulation. The renal clearance (CL(renal)) increased and the hepatic clearance (CL(hepatic)) decreased with the micelle formulation, as compared to the standard vehicle. The micellar formulation showed a 1.3-fold increase in the half-life (t(1/2)) of the drug in serum and 1.2-fold increase in t(1/2) of urine. As expected, because it circulated longer in the blood, we also observed a 1.7-fold increase in the volume of distribution (V(d)) with this micelle formulation compared to the standard formulation. Overall, the new formulation of 17-AAG in PEO-b-PDLLA (12:6 kDa) micelles resulted in a favorable 150-fold increase in solubility over 17-AAG alone, while retaining similar properties to the standard formulation. Our data indicates that the nanocarrier system can retain the pharmacokinetic disposition of 17-AAG without the need for toxic agents such as CrEL and EtOH.
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http://dx.doi.org/10.1002/jps.21509DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2649998PMC
April 2009

Formulation of a geldanamycin prodrug in mPEG-b-PCL micelles greatly enhances tolerability and pharmacokinetics in rats.

J Control Release 2008 Jul 25;129(1):33-40. Epub 2008 Mar 25.

Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047-3729, USA.

Geldanamycin (GA) and its analogues inhibit heat shock protein 90 (Hsp90) and have shown significant antitumor activity in vivo; however, clinical development of GA has been hampered by its poor solubility and severe hepatotoxicity. More soluble analogues, such as 17-DMAG and 17-AAG, are easier to formulate, and have progressed through early clinical trials. However the large volume of distribution and systemic toxicity associated with these analogues may limit their distribution into tumors, thereby severely reducing efficacy and increasing non-specific toxicities. We have evaluated a formulation of a lipophilic GA prodrug, 17'GAC(16)Br encapsulated in methoxy-capped poly(ethylene glycol)-block-poly(epsilon-caprolactone) (mPEG-b-PCL) micelles, by comparing it to free 17-DMAG at 10 mg/kg in rats. mPEG-b-PCL micelles reported herein demonstrated substantial sustained release and conversion of 17'GAC(16)Br into 17'GAOH at significantly greater levels in all tissues analyzed compared to the free drug, allowing for a 72-fold enhancement in the AUC, a 21-fold decrease in V(d), an 11-fold decrease in CL(tot), and a 2-fold and 7-fold enhancement in the overall MRT of 17'GAC(16)Br and 17'GAOH, respectively. Importantly, the micellar formulation exhibited lower systemic toxicity than 17-DMAG, with a MTD >200 mg/kg and a 2000-fold enhancement in the AUC. 17'GAC(16)Br in micelles were poorly cleared renally, in contrast to 17-DMAG and 17'GAOH, but showed preferential accumulation and prodrug conversion in reticuloendothelial organs of normal animals. Overall, the data indicate that this nanocarrier system is a promising alternative to the current 17-DMAG formulation and offers excellent potential for further pre-clinical and clinical cancer studies.
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http://dx.doi.org/10.1016/j.jconrel.2008.03.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2492396PMC
July 2008

Poly(aspartate-g-PEI800), a polyethylenimine analogue of low toxicity and high transfection efficiency for gene delivery.

Biomaterials 2007 Nov 10;28(32):4889-900. Epub 2007 Aug 10.

Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705-2222, USA.

High-molecular-weight polyethylenimine (25 kDa, PEI25k) is one of the most common cationic polymers utilized in non-viral gene therapy. However, its methylene backbone (-CH(2)CH(2)N(x)-) and high charge density can result in poor biodegradability and high toxicity to cells. We hypothesize that optimizing the polymer length and charge density of PEI analogues may result in decreased toxicity and higher transfection efficiency, and improved biocompatibility in vivo. A series of PEI analogues with controlled molecular weight and charge density were synthesized by grafting low-molecular-weight PEI800 (800 Da) to a polyaspartate peptide backbone of varying degrees of polymerization. The optimum polymer had a degree of polymerization of 65 with an average of 16 PEI800 groups conjugated to it. All of the polycations investigated in the study caused inflammation and apoptosis/necrosis in the liver and spleen of rodents 24h post-injection; however, by day 5, the optimized poly(aspartate-g-PEI800) polymer and PEI800 did not show tissue damage or apoptosis, whereas PEI25k exhibited evidence of apoptosis/necrosis in the kidneys and spleen. Our study points to the need to optimize gene carriers to minimize toxicity, especially important for the safe delivery of therapeutic genes to explicit organs.
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http://dx.doi.org/10.1016/j.biomaterials.2007.07.043DOI Listing
November 2007

pH-responsive Multi-PEGylated dual cationic nanoparticles enable charge modulations for safe gene delivery.

ChemMedChem 2007 Sep;2(9):1321-7

Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705-2222, USA.

In gene therapy, the cytotoxicity of many polycations is undesirable and has been attributed to nonspecific membrane destabilizing effects and intracellular polyplex-mediated toxicity. To help prolong the pharmacokinetic profile of nonviral vehicles for gene delivery, the cationic surface charge of current systems is typically shielded through the conjugation of polyethylene glycol (PEG) chains to the particle surface. However, the design of an intelligent polycation with environment-sensing charge modulations is essential to minimize cytotoxicity and enhance gene expression. We have designed a novel di-cationic block copolymer, poly(aspartate-hydrazide)-block-poly(L-lysine), capable of pH-mediated endosomal membrane disruption based on charge interactions, which has negligible toxicity elsewhere to the cell. The poly(L-lysine) segment, with a high pK(a) value of approximately 9.4, preferentially forms a poly-ion complex with the negative phosphate groups of pDNA, whereas the pH-responsive poly(aspartate-hydrazide) segment, with the comparatively lower pK(a) approximately 5.0, is characterized by a substantial fraction of unprotonated amino groups at physiological pH. As a consequence, complexation between such a polymer and pDNA leads to the formation of a two-layered nanoparticle. In particular, the nanoparticle possesses an unprotonated pH-responsive segment to serve as both a scaffold for acid-labile linkages of various moieties such as aldehyde-PEG and to transition from neutral to charged for disrupting endosomal membranes, and safely enhancing gene expression. Our system supports an endosomal escape mechanism based on charge interactions rather than the proton-sponge effect, and may be an important step towards engineering new classes of intelligent nonviral vectors.
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http://dx.doi.org/10.1002/cmdc.200700093DOI Listing
September 2007

Biotin-triggered release of poly(ethylene glycol)-avidin from biotinylated polyethylenimine enhances in vitro gene expression.

Bioconjug Chem 2007 May-Jun;18(3):746-53. Epub 2007 Mar 22.

Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, Wisconsin 53705-2222, USA.

Covalently poly(ethylene glycol) (PEG)-ylated polyethylenimine (PEI)/pDNA complexes display prolonged blood circulation profiles compared with PEI/pDNA complexes, but such PEGylated particles may not be suitable for tumor targeting due to low interaction with cell membranes, low internalization, and low gene expression. Noncovalent PEGylation of cationic particles via PEG-avidin/biotin-PEI is an attempt to bridge the gap between the positive attributes of PEG (prolonged particle circulation) and the positive attributes of nontoxic cationic polymers (enhanced cell interactions) for greater gene expression. Our polymer, 2PEG-avidin/biotin-PEI8, forms salt-stable particles ( approximately 100 nm) under physiologic conditions with a minimum of two 2PEG-avidin molecules bound per polymer chain (biotin-PEI8, 8 biotins/PEI). Following 10 days of incubation with 3000-fold excess biotin, 2PEG-avidin completely dissociated from biotin-PEI8, and gene expression was increased 2.1-32-fold in various cell lines when the desirable transfection feature of the cationic polymer was retained. This new PEGylation approach has implications for generally improving the clinical aspect of gene delivery via a two-step therapeutic strategy: (1) intravenous injection of noncovalent PEG-avidin/biotin-polycation nanoparticles for prolonged circulation, followed by (2) temporal release of PEG-avidin from biotin-polycation through either endogenous biotin or intravenous injection of biotin.
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http://dx.doi.org/10.1021/bc0602883DOI Listing
August 2007

PEGylation of yeast cytosine deaminase for pretargeting.

J Pharm Sci 2005 Jun;94(6):1249-58

Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705-2222, USA.

Yeast cytosine deaminase (yCD) was cloned, expressed, and purified by affinity chromatography. We have characterized the products resulting from covalent attachment of 2-4 PEG chains on yCD and determined the major and minor isomers for each respective conjugate. The results show that for non-covalently associated homodimers, it is possible to characterize and deduce PEGylation levels on individual subunits through the concurrent use of size exclusion chromatography (SEC), MALDI-TOF MS, and SDS-PAGE gels. The results also show that contrary to what we expected, attaching more than two PEG chains to yCD decreased its stability. Enzymatic activity studies revealed that the fusion of an N-terminus purification tag on yCD has no significant effect on 5-fluorocytosine or cytosine affinity, with apparent turnover rates remaining within 10(5) M(-1) . s(-1). Stability studies at 37 degrees C revealed that t1/2 = 8-9 h for yCD and 2mPEG(5K)-yCD, whereas for 3-, 4mPEG(5K)-yCD and yCD/BSA, t(1/2) < 2 h. Incubation of BSA with yCD also decreased enzyme stability over prolonged incubation at 37 degrees C. This finding is important if yCD is to be used in a pretargeting strategy.
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http://dx.doi.org/10.1002/jps.20354DOI Listing
June 2005
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