Publications by authors named "Jacob Schimelman"

11 Publications

  • Page 1 of 1

Bioprinting of dual ECM scaffolds encapsulating limbal stem/progenitor cells in active and quiescent statuses.

Biofabrication 2021 08 13;13(4). Epub 2021 Aug 13.

Department of NanoEngineering, University of California San Diego, La Jolla, CA 92093, United States of America.

Limbal stem cell deficiency and corneal disorders are among the top global threats for human vision. Emerging therapies that integrate stem cell transplantation with engineered hydrogel scaffolds for biological and mechanical support are becoming a rising trend in the field. However, methods for high-throughput fabrication of hydrogel scaffolds, as well as knowledge of the interaction between limbal stem/progenitor cells (LSCs) and the surrounding extracellular matrix (ECM) are still much needed. Here, we employed digital light processing (DLP)-based bioprinting to fabricate hydrogel scaffolds encapsulating primary LSCs and studied the ECM-dependent LSC phenotypes. The DLP-based bioprinting with gelatin methacrylate (GelMA) or hyaluronic acid glycidyl methacrylate (HAGM) generated microscale hydrogel scaffolds that could support the viability of the encapsulated primary rabbit LSCs (rbLSCs) in culture. Immunocytochemistry and transcriptional analysis showed that the encapsulated rbLSCs remained active in GelMA-based scaffolds while exhibited quiescence in the HAGM-based scaffolds. The primary human LSCs encapsulated within bioprinted scaffolds showed consistent ECM-dependent active/quiescent statuses. Based on these results, we have developed a novel bioprinted dual ECM 'Yin-Yang' model encapsulating LSCs to support both active and quiescent statues. Our findings provide valuable insights towards stem cell therapies and regenerative medicine for corneal reconstruction.
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http://dx.doi.org/10.1088/1758-5090/ac1992DOI Listing
August 2021

Rapid 3D Bioprinting of Glioblastoma Model Mimicking Native Biophysical Heterogeneity.

Small 2021 04 27;17(15):e2006050. Epub 2021 Jan 27.

Department of NanoEngineering, University of California San Diego, La Jolla, CA, 92093, USA.

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor characterized by high cellular and molecular heterogeneity, hypervascularization, and innate drug resistance. Cellular components and extracellular matrix (ECM) are the two primary sources of heterogeneity in GBM. Here, biomimetic tri-regional GBM models with tumor regions, acellular ECM regions, and an endothelial region with regional stiffnesses patterned corresponding to the GBM stroma, pathological or normal brain parenchyma, and brain capillaries, are developed. Patient-derived GBM cells, human endothelial cells, and hyaluronic acid derivatives are used to generate a species-matched and biochemically relevant microenvironment. This in vitro study demonstrates that biophysical cues are involved in various tumor cell behaviors and angiogenic potentials and promote different molecular subtypes of GBM. The stiff models are enriched in the mesenchymal subtype, exhibit diffuse invasion of tumor cells, and induce protruding angiogenesis and higher drug resistance to temozolomide. Meanwhile, the soft models demonstrate enrichment in the classical subtype and support expansive cell growth. The three-dimensional bioprinting technology utilized in this study enables rapid, flexible, and reproducible patient-specific GBM modeling with biophysical heterogeneity that can be employed by future studies as a tunable system to interrogate GBM disease mechanisms and screen drug compounds.
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http://dx.doi.org/10.1002/smll.202006050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8049977PMC
April 2021

Rapid bioprinting of conjunctival stem cell micro-constructs for subconjunctival ocular injection.

Biomaterials 2021 01 23;267:120462. Epub 2020 Oct 23.

Department of NanoEngineering, University of California San Diego, La Jolla, CA, 92093, USA; Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093, USA; Department of Bioengineering, University of California San Diego, La Jolla, CA, 92093, USA. Electronic address:

Ocular surface diseases including conjunctival disorders are multifactorial progressive conditions that can severely affect vision and quality of life. In recent years, stem cell therapies based on conjunctival stem cells (CjSCs) have become a potential solution for treating ocular surface diseases. However, neither an efficient culture of CjSCs nor the development of a minimally invasive ocular surface CjSC transplantation therapy has been reported. Here, we developed a robust in vitro expansion method for primary rabbit-derived CjSCs and applied digital light processing (DLP)-based bioprinting to produce CjSC-loaded hydrogel micro-constructs for injectable delivery. Expansion medium containing small molecule cocktail generated fast dividing and highly homogenous CjSCs for more than 10 passages in feeder-free culture. Bioprinted hydrogel micro-constructs with tunable mechanical properties enabled the 3D culture of CjSCs while supporting viability, stem cell phenotype, and differentiation potency into conjunctival goblet cells. These hydrogel micro-constructs were well-suited for scalable dynamic suspension culture of CjSCs and were successfully delivered to the bulbar conjunctival epithelium via minimally invasive subconjunctival injection. This work integrates novel cell culture strategies with bioprinting to develop a clinically relevant injectable-delivery approach for CjSCs towards the stem cell therapies for the treatment of ocular surface diseases.
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http://dx.doi.org/10.1016/j.biomaterials.2020.120462DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7719077PMC
January 2021

3D printing of a biocompatible double network elastomer with digital control of mechanical properties.

Adv Funct Mater 2020 Apr 19;30(14). Epub 2020 Feb 19.

Department of NanoEngineering, Chemical Engineering Program, Materials Science and Engineering Program, Department of Bioengineering, University of California San Diego, La Jolla, CA 92093.

The majority of 3D-printed biodegradable biomaterials are brittle, limiting their potential application to compliant tissues. Poly (glycerol sebacate) acrylate (PGSA) is a synthetic biodegradable and biocompatible elastomer, compatible with light-based 3D printing. In this work we employed digital-light-processing (DLP)-based 3D printing to create a complex PGSA network structure. Nature-inspired double network (DN) structures with two geometrically interconnected segments with different mechanical properties were printed from the same material in a single shot. Such capability has not been demonstrated by any other fabrication technique. The biocompatibility of PGSA after 3D printing was confirmed via cell-viability analysis. We used a finite element analysis (FEA) model to predict the failure of the DN structure under uniaxial tension. FEA confirmed the soft segments act as sacrificial elements while the hard segments retain structural integrity. The simulation demonstrated that the DN design absorbs 100% more energy before rupture than the network structure made by single exposure condition (SN), doubling the toughness of the overall structure. Using the FEA-informed design, a new DN structure was printed and the FEA predicted tensile test results agreed with tensile testing of the printed structure. This work demonstrated how geometrically-optimized material design can be easily and rapidly achieved by using DLP-based 3D printing, where well-defined patterns of different stiffnesses can be simultaneously formed using the same elastic biomaterial, and overall mechanical properties can be specifically optimized for different biomedical applications.
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http://dx.doi.org/10.1002/adfm.201910391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7566974PMC
April 2020

High-fidelity 3D Printing using Flashing Photopolymerization.

Addit Manuf 2019 Dec 19;30. Epub 2019 Aug 19.

Department of NanoEngineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California, 92093, USA.

Photopolymerization-based 3D printing has emerged as a promising technique to fabricate 3D structures. However, during the printing process, polymerized materials such as hydrogels often become highly light-scattering, thus perturbing incident light distribution and thereby deteriorating the final print resolution. To overcome this scattering-induced resolution deterioration, we developed a novel method termed flashing photopolymerization (FPP). Our FPP approach is informed by the fundamental kinetics of photopolymerization reactions, where light exposure is delivered in millisecond-scale 'flashes', as opposed to continuous light exposure. During the period of flash exposure, the prepolymer material negligibly scatters light. The material then polymerizes and opacifies in absence of light, therefore the exposure pattern is not perturbed by scattering. Compared to the conventional use of a continuous wave (CW) light source, the FPP fabrication resolution is improved. FPP also shows little dependency on the exposure, thus minimizing trial-and-error type optimization. Using FPP, we demonstrate its use in generating high-fidelity 3D printed constructs.
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http://dx.doi.org/10.1016/j.addma.2019.100834DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442265PMC
December 2019

A sequential 3D bioprinting and orthogonal bioconjugation approach for precision tissue engineering.

Biomaterials 2020 11 9;258:120294. Epub 2020 Aug 9.

Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA; Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA; Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA; Chemical Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. Electronic address:

Recent advances in 3D bioprinting have transformed the tissue engineering landscape by enabling the controlled placement of cells, biomaterials, and bioactive agents for the biofabrication of living tissues and organs. However, the application of 3D bioprinting is limited by the availability of cytocompatible and printable biomaterials that recapitulate properties of native tissues. Here, we developed an integrated 3D projection bioprinting and orthogonal photoconjugation platform for precision tissue engineering of tailored microenvironments. By using a photoreactive thiol-ene gelatin bioink, soft hydrogels can be bioprinted into complex geometries and photopatterned with bioactive moieties in a rapid and scalable manner via digital light projection (DLP) technology. This enables localized modulation of biophysical properties such as stiffness and microarchitecture as well as precise control over spatial distribution and concentration of immobilized functional groups. As such, well-defined properties can be directly incorporated using a single platform to produce desired tissue-specific functions within bioprinted constructs. We demonstrated high viability of encapsulated endothelial cells and human cardiomyocytes using our dual process and fabricated tissue constructs functionalized with VEGF peptide mimics to induce guided endothelial cell growth for programmable vascularization. This work represents a pivotal step in engineering multifunctional constructs with unprecedented control, precision, and versatility for the rational design of biomimetic tissues.
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http://dx.doi.org/10.1016/j.biomaterials.2020.120294DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7489302PMC
November 2020

Three-dimensional bioprinted glioblastoma microenvironments model cellular dependencies and immune interactions.

Cell Res 2020 10 4;30(10):833-853. Epub 2020 Jun 4.

Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA, 92037, USA.

Brain tumors are dynamic complex ecosystems with multiple cell types. To model the brain tumor microenvironment in a reproducible and scalable system, we developed a rapid three-dimensional (3D) bioprinting method to construct clinically relevant biomimetic tissue models. In recurrent glioblastoma, macrophages/microglia prominently contribute to the tumor mass. To parse the function of macrophages in 3D, we compared the growth of glioblastoma stem cells (GSCs) alone or with astrocytes and neural precursor cells in a hyaluronic acid-rich hydrogel, with or without macrophage. Bioprinted constructs integrating macrophage recapitulate patient-derived transcriptional profiles predictive of patient survival, maintenance of stemness, invasion, and drug resistance. Whole-genome CRISPR screening with bioprinted complex systems identified unique molecular dependencies in GSCs, relative to sphere culture. Multicellular bioprinted models serve as a scalable and physiologic platform to interrogate drug sensitivity, cellular crosstalk, invasion, context-specific functional dependencies, as well as immunologic interactions in a species-matched neural environment.
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http://dx.doi.org/10.1038/s41422-020-0338-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608409PMC
October 2020

Photopolymerizable Biomaterials and Light-Based 3D Printing Strategies for Biomedical Applications.

Chem Rev 2020 10 23;120(19):10695-10743. Epub 2020 Apr 23.

Department of NanoEngineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States.

Since the advent of additive manufacturing, known commonly as 3D printing, this technology has revolutionized the biofabrication landscape and driven numerous pivotal advancements in tissue engineering and regenerative medicine. Many 3D printing methods were developed in short course after Charles Hull first introduced the power of stereolithography to the world. However, materials development was not met with the same enthusiasm and remained the bottleneck in the field for some time. Only in the past decade has there been deliberate development to expand the materials toolbox for 3D printing applications to meet the true potential of 3D printing technologies. Herein, we review the development of biomaterials suited for light-based 3D printing modalities with an emphasis on bioprinting applications. We discuss the chemical mechanisms that govern photopolymerization and highlight the application of natural, synthetic, and composite biomaterials as 3D printed hydrogels. Because the quality of a 3D printed construct is highly dependent on both the material properties and processing technique, we included a final section on the theoretical and practical aspects behind light-based 3D printing as well as ways to employ that knowledge to troubleshoot and standardize the optimization of printing parameters.
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http://dx.doi.org/10.1021/acs.chemrev.9b00810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7572843PMC
October 2020

Rapid continuous 3D printing of customizable peripheral nerve guidance conduits.

Mater Today (Kidlington) 2018 Nov 27;21(9):951-959. Epub 2018 Apr 27.

Department of NanoEngineering, University of California San Diego, La Jolla, CA 92093, United States.

Engineered nerve guidance conduits (NGCs) have been demonstrated for repairing peripheral nerve injuries. However, there remains a need for an advanced biofabrication system to build NGCs with complex architectures, tunable material properties, and customizable geometrical control. Here, a rapid continuous 3D-printing platform was developed to print customizable NGCs with unprecedented resolution, speed, flexibility, and scalability. A variety of NGC designs varying in complexity and size were created including a life-size biomimetic branched human facial NGC. implantation of NGCs with microchannels into complete sciatic nerve transections of mouse models demonstrated the effective directional guidance of regenerating sciatic nerves via branching into the microchannels and extending toward the distal end of the injury site. Histological staining and immunostaining further confirmed the progressive directional nerve regeneration and branching behavior across the entire NGC length. Observational and functional tests, including the von Frey threshold test and thermal test, showed promising recovery of motor function and sensation in the ipsilateral limbs grafted with the 3D-printed NGCs.
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http://dx.doi.org/10.1016/j.mattod.2018.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538503PMC
November 2018

X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues.

Sci Rep 2016 06 2;6:27079. Epub 2016 Jun 2.

Department of Physics, University of Massachusetts, Amherst, MA 01003, United States.

Observed in the folds of guanine-rich oligonucleotides, non-canonical G-quadruplex structures are based on G-quartets formed by hydrogen bonding and cation-coordination of guanosines. In dilute 5'-guanosine monophosphate (GMP) solutions, G-quartets form by the self-assembly of four GMP nucleotides. We use x-ray diffraction to characterize the columnar liquid-crystalline mesophases in concentrated solutions of various model G-quadruplexes. We then probe the transitions between mesophases by varying the PEG solution osmotic pressure, thus mimicking in vivo molecular crowding conditions. Using the GMP-quadruplex, built by the stacking of G-quartets with no covalent linking between them, as the baseline, we report the liquid-crystalline phase behaviors of two other related G-quadruplexes: (i) the intramolecular parallel-stranded G-quadruplex formed by the 22-mer four-repeat human telomeric sequence AG3(TTAG3)3 and (ii) the intermolecular parallel-stranded G-quadruplex formed by the TG4T oligonucleotides. Finally, we compare the mesophases of the G-quadruplexes, under PEG-induced crowding conditions, with the corresponding mesophases of the canonical duplex and triplex DNA analogues.
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http://dx.doi.org/10.1038/srep27079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4890033PMC
June 2016

Optical properties and electronic transitions of DNA oligonucleotides as a function of composition and stacking sequence.

Phys Chem Chem Phys 2015 Feb;17(6):4589-99

Department of Biomedical Engineering, Case Western Reserve University, Schools of Medicine and Engineering, Cleveland, Ohio 44106, USA.

The role of base pair composition and stacking sequence in the optical properties and electronic transitions of DNA is of fundamental interest. We present and compare the optical properties of DNA oligonucleotides (AT)10, (AT)5(GC)5, and (AT-GC)5 using both ab initio methods and UV-vis molar absorbance measurements. Our data indicate a strong dependence of both the position and intensity of UV absorbance features on oligonucleotide composition and stacking sequence. The partial densities of states for each oligonucleotide indicate that the valence band edge arises from a feature associated with the PO4(3-) complex anion, and the conduction band edge arises from anti-bonding states in DNA base pairs. The results show a strong correspondence between the ab initio and experimentally determined optical properties. These results highlight the benefit of full spectral analysis of DNA, as opposed to reductive methods that consider only the 260 nm absorbance (A260) or simple purity ratios, such as A260/A230 or A260/A280, and suggest that the slope of the absorption edge onset may provide a useful metric for the degree of base pair stacking in DNA. These insights may prove useful for applications in biology, bioelectronics, and mesoscale self-assembly.
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http://dx.doi.org/10.1039/c4cp03395gDOI Listing
February 2015
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