Genetically Encoded XTEN-based Hydrogels with Tunable Viscoelasticity and Biodegradability for Injectable Cell Therapies.

While direct cell transplantation holds great promise in treating many debilitating diseases, poor cell survival and engraftment following injection have limited effective clinical translation. Though injectable biomaterials offer protection against membrane-damaging extensional flow and supply a supportive 3D environment in vivo that ultimately improves cell retention and therapeutic costs, most are created from synthetic or naturally harvested polymers that are immunogenic and/or chemically ill-defined. This work presents a shear-thinning and self-healing telechelic recombinant protein-based hydrogel designed around XTEN - a well-expressible, non-immunogenic, and intrinsically disordered polypeptide previously evolved as a genetically encoded alternative to PEGylation to "eXTENd" the in vivo half-life of fused protein therapeutics. By flanking XTEN with self-associating coil domains derived from cartilage oligomeric matrix protein, single-component physically crosslinked hydrogels exhibiting rapid shear thinning and self-healing through homopentameric coiled-coil bundling are formed. Individual and combined point mutations that variably stabilize coil association enables a straightforward method to genetically program material viscoelasticity and biodegradability. Finally, these materials protect and sustain viability of encapsulated human fibroblasts, hepatocytes, embryonic kidney (HEK), and embryonic stem-cell-derived cardiomyocytes (hESC-CMs) through culture, injection, and transcutaneous implantation in mice. These injectable XTEN-based hydrogels show promise for both in vitro cell culture and in vivo cell transplantation applications.

Photoreactive Carboxybetaine Copolymers Impart Biocompatibility and Inhibit Plasticizer Leaching on Polyvinyl Chloride.

Protein and cell interactions on implanted, blood-contacting medical device surfaces can lead to adverse biological reactions. Medical-grade poly(vinyl chloride) (PVC) materials have been used for decades, particularly as blood-contacting tubes and containers. However, there are numerous concerns with their performance including platelet activation, complement activation, and thrombin generation and also leaching of plasticizers, particularly in clinical applications. Here, we report a surface modification method that can dramatically prevent blood protein adsorption, human platelet activation, and complement activation on commercial medical-grade PVC materials under various test conditions. The surface modification can be accomplished through simple dip-coating followed by light illumination utilizing biocompatible polymers comprising zwitterionic carboxybetaine (CB) moieties and photosensitive cross-linking moieties. This surface treatment can be manufactured routinely at small or large scales and can impart to commercial PVC materials superhydrophilicity and nonfouling capability. Furthermore, the polymer effectively prevented leaching of plasticizers out from commercial medical-grade PVC materials. This coating technique is readily applicable to many other polymers and medical devices requiring surfaces that will enhance performance in clinical settings.

Zwitterionic carboxybetaine polymers extend the shelf-life of human platelets.

The shelf-life of human platelets preserved in vitro for therapeutic transfusion is limited because of bacterial contamination and platelet storage lesion (PSL). The PSL is the predominant factor and limiting unfavorable interactions between the platelets and the non-biocompatible storage bag surfaces is the key to alleviate PSL. Here we describe a surface modification method for biocompatible platelet storage bags that dramatically extends platelet shelf-life beyond the current US Food and Drug Administration (FDA) standards of 5 days. The surface coating of the bags can be achieved through a simple yet effective dip-coating and light-irradiation method using a biocompatible polymer. The biocompatible polymers with tunable functional groups can be routinely fabricated at any scale and impart super-hydrophilicity and non-fouling capability on commercial hydrophobic platelet storage bags. As critical parameters reflecting the platelets quality, the activation level and binding affinity with von Willebrand factor (VWF) of the platelets stored in the biocompatible platelet bags at 8 days are comparable with those in the commercial bags at 5 days. This technique also demonstrates promise for a wide range of medical and engineering applications requiring biocompatible surfaces. STATEMENT OF SIGNIFICANCE: Current standard platelet preservation techniques agitate platelets at room temperature (20-24 °C) inside a hydrophobic (e.g., polyvinyl chloride (PVC)) storage bag, thereby allowing preservation of platelets only for 5 days. A key factor leading to quality loss is the unfavorable interaction between the platelets and the non-biocompatible storage bag surfaces. Here, a surface modification method for biocompatible platelet storage bags has been created to dramatically extend platelet shelf-life beyond the current FDA standards of 5 days. The surface coating of the bags can be achieved via a simple yet effective dip-coating and light-irradiation method using a carboxybetaine polymer. This technique is also applicable to many other applications requiring biocompatible surfaces.