1. New Publication: Computational modeling of water uptake for degradable materials in medical devices

Degradable materials are very important in fabricating biomedical devices. After implantation, they do not need to be removed; rather, under ideal conditions, the implant site repairs itself while the device is resorbed. In comparison, nondegradable materials often need to be surgically removed after their purpose has been achieved, thus subjecting the patient to a second surgery that potentially exposes them to more complications. Degradable devices can be used in a broad range of applications such as vascular stents, vascular bypass grafts, bone fixation devices, and soft tissue replacement scaffolds. Degradable biomaterials have a wide range of requirements depending on the particular clinical application. Parameters such as chemical structure, composition, porosity, and device geometry determine surface and bulk properties of an implant, and thus, they are critical to the selection of the material. One important characteristic of degradable biomaterials is their water uptake versus time, as it is crucial for the determination of how long a polymeric device will reside in the body before erosion leads to the ultimate removal of the device from the implant site. Water uptake affects degradation, swelling, mechanical, and adhesive properties; also it determines drug stability, drug release profile, and biological response. Current methods used to measure water uptake versus time are labor intensive and time consuming. Depending on the polymer, water uptake can take days to weeks to equilibrate. There are potentially very large libraries of polymeric biomaterials, which make it impractical to measure these parameters experimentally for each polymer.  Computational modeling is a useful tool to minimize the number of experiments needed to characterize a polymer library. Our research has two objectives: (i) the development of computational models for water uptake versus time based upon experimental data from a small subset of polymers in a library and (ii) the application of these models to predict water uptake for an entire library of polymers. The main challenge of this research is to model and predict properties that change over time with particular kinetics using a small set of experimental data. As a model system, a library of L-tyrosine-derived polyarylates was used. Kohn and collaborators used this library to discover promising lead polymers for several medical applications, such as bone pins, hernia repair devices, and an antibacterial sleeve that protects recipients of implanted cardiac assist devices from potentially life-threatening infections. Changes in polymer backbone or pendent chain length affect polymer properties such as and hydrophobicity. In this study we investigate the effect of polymer backbone and pendent chain on the water uptake profiles of polymer films.

Click here to read the full publication.

2. Video: Self-Assembly of Polymer Micelle

This video represents collaborative work between the New Jersey Center for Biomaterials and the Dutt Research Laboratory, both located at Rutgers University.

3. Recently published article on modeling CAC and experimental validation

Dr. Joachim Kohn and the NJCBM research group have recently published the results of their collaboration with Meenakshi Dutt’s lab in the Rutgers Biomedical Engineering Department on a promising new nanoparticle construction for drug delivery. The study was accepted by The Journal of Physical Chemistry (an ACS publication) and recently made available online at http://pubsdc3.acs.org/doi/full/10.1021/acs.jpcb.5b12594 Nanotechnology enables the manipulation of materials on atomic, molecular, and supramolecular scales. In the field of medicine, this often involves the application of various bio-compatible materials in nanoparticle form, which can be used to deliver drugs more efficiently. The drug loading efficiency of nanoparticles is determined by several factors, particularly the chemical affinity of the loaded drug for the nanoparticle core. Amphiphilic copolymers can be designed to self-assemble with low critical aggregation concentration (CAC), thus providing stable aqueous dispersions of lipophilic drugs by maintaining structural integrity. Computational methods have been adopted to measure the CAC of block copolymers. A unique advantage of computational methods is the ability to determine CAC values of drug delivery systems based on a virtual library of numerous ABA block polymers.The corresponding author of this paper, Meenakshi Dutt, has developed a computational model that can predict the CAC without having to make the nanoparticles first. In our publication, these predictions were immediately validated experimentally.

4. Development of new inks for 3D printers

Professor Murat Guvendiren at the New Jersey Center for Biomaterials leads a team of researchers working on the development of new inks for 3D printers. 3D printing is an increasingly common technique to fabricate scaffolds and devices for tissue engineering applications. But, one of the major bottlenecks that limits the widespread acceptance of 3D printing in biomanufacturing is the lack of diversity in “biomaterial inks”. Prof. Guvendiren’s team is currently submitting a comprehensive review that highlights recent advances in biomaterial ink development and design considerations moving forward. The review will also include a brief overview of 3D printing technologies focusing on ink design parameters.

5. NJCBM Director Dr. Joachim Kohn and Co-Authors Publish in Nature Communications on 3D Scaffolds for Neuron Regrowth

Neurodegenerative diseases and central nervous system injuries cause life-changing motor and sensory deficits as a result of severe loss of neurons in the central nervous system.  Cell replacement therapies using patient-derived cells reprogrammed into neurons have the potential to restore normal function, however, typical cell transplantation involves forcefully detaching cells from growth surfaces and result in limited transplanted cell survival, functionality, and engraftment.  In this collaboration between Professor Moghe’s lab and the NJCBM, an optimized molecular composite of a tyrosine-derived polycarbonate was used to create three-dimensional polymeric scaffolds with tunable microscale topography.  The maturation of reprogrammed neuronal populations was enhanced on some scaffold geometries, and these cell populations were observed to have significantly fewer dividing and potentially tumorigenic cells.  Scaffold-supported reprogrammed neuronal cell population successfully engrafted into hippocampal brain slices, with a 3.5-fold improvement in neurite outgrowth and increased action potential firing relative to dissociated single cells.  Scaffolds also improved the survival rate of neurons transplanted into mouse brain 38-fold.  Overall, these studies demonstrate that the development of optimized polymeric scaffolds was a critical component of the successful cell transplantation reported here. Cell-scaffold interactions should be a major consideration guiding the design of scaffolds in transplanting neuronal cell populations.

6. Seminal Study Comparing Four Sterilization Techniques for Biomaterials To Be Published

A team of scientists from the New Jersey Center for Biomaterials and the Johnson & Johnson Sterility Assurance Group are finalizing a seminal publication, describing a comparison of 4 industrially relevant sterilization methods for medical implants.  As part of a successful commercialization strategy, the selection of a suitable method for the FDA-required terminal sterilization of the implant is a critical task.  All currently known sterilization methods can adversely affect the physicochemical properties of the polymers used as implant components. This study explores the effects of different sterilization modalities (ethylene oxide (EO), vaporized hydrogen peroxide (VHP), gamma (γ) radiation, and electron beam (E-beam)) on the chemical, structural and morphological properties of polymers with ether, carbonate, carboxylic acid, amide and ester functionalities using a family of poly(ethylene glycol) (PEG) containing tyrosine-derived polycarbonates (TyrPCs) as model compounds.  Test polymers were selected to include slow, medium, fast and ultra-fast degrading polymers, representing a series of materials with increasing sensitivity to moisture, temperature, a radiation. Each of the sterilization modalities affected the tested polymers differently and no single sterilization technique emerged as being universally applicable for all test samples.  This study illuminates the critical importance of considering the chemical composition of the polymer when selecting a sterilization method, and provides suggested conditions for each of the tested sterilization methods.

7. Rat Models Questioned in Nerve Regeneration