PEG-Immobilized Keratin for Protein Drug Sequestration and pH-Mediated Delivery

Abstract

Protein drugs like growth factors are promising therapeutics for damaged-tissue repair. Their local delivery often requires biomaterial carriers for achieving the therapeutic dose range while extending efficacy. In this study, polyethylene glycol (PEG) and keratin were crosslinked and used as sponge-like scaffolds (KTN-PEG) to absorb test proteins with different isoelectric points (pI): albumin (~5), hemoglobin (~7), and lysozyme (~11). The protein release kinetics was influenced by charge at physiological pH 7.4. The keratin network, with pI 5.3, electrostatically attracted lysozyme and repulsed albumin generating the release rate profile: albumin > hemoglobin > lysozyme. However, under acidic conditions (pH 4), all proteins including keratins were positively charged and consequently intermolecular repulsion altered the release hierarchy, now determined by size (MW) diffusion: lysozyme (14 kDa) > hemoglobin (64 kDa) > albumin (66 kDa). Vascular endothelial growth factor C (VEGF-C), with properties comparable to lysozyme, was absorbed into the KTN-PEG scaffold. Endothelial cells cultured on this substrate had significantly larger numbers than on scaffolds without VEGF-C suggesting that the ionically bound and retained growth factor at neutral pH indirectly increased acute cell attachment and viability. PEG and keratin based sequestrations of proteins with basic pIs are therefore a feasible strategy with potential applications for selective biologics delivery.

Self-assembly behavior of the keratose proteins extracted from oxidized Ovis aries wool fibers

“…Different from the other proteins, it contains quite high cysteine content (5-10 mol%) that promotes its mechanical, chemical and thermal stability features due to the disulfide bonds present in their structures [19][20][21]. Like the other biopolymers from biological origins such as collagen, elastin and chitosan, keratin alone and mixed with other polymers have been also tested in various biomedical applications such as delivery of bioactive agents [22][23][24], wound healing [17,[25][26][27], and bone tissue engineering [28][29][30]. It has been almost genuinely proven that keratins are promising candidates as sustainable biomaterials due to their abundance, low cost and biocompatibility.…”

Study on Keratin/PEGDA Composite Hydrogel with the Addition of Varied Hair Protein Fractions

“…Moreover, previous studies have observed that cell viability can be maintained when PEGDA or keratin biomaterials (e.g., a mixture of KAPs and KIFs) are used . Similar results were obtained in the present study, where a proliferation of cells was observed following a treatment with KAPs-PEGDA and KIFs-PEGDA gel extracts.…”

“…Reduced keratin proteins with free thiols can be gelled by reforming disulfide bonds. The photopolymerization of the thiolene reaction also links keratin with PEGDA . In this manner, the keratin and PEGDA networks are combined simultaneously to form the composite hydrogel.…”

“…For example, keratins have been combined with PEGDA to improve the hydrogels’ mechanical properties, biological activity, and printing abilities. Moreover, the photo-cross-linking mechanism of keratin-PEGDA composite renders it ideal for fabricating tissues with various architectural designs, which can be applied to oral tissue regeneration, wound dressings, drug delivery, or hemostatic materials. − …”

Synthesis of Hydrogel Films Based on PVA, PVP, Starch and Keratin Extracted From Chicken Feathers Wastes for the Potential Biomedical Applications

“…The hydrogel samples have been cut to small sizes (2cm x 2cm) and then placed in a dialysis bag and closed tightly by both sides using plastic clips then placed into a 50 ml tube and filled with 40 ml of PBS and pH 7.4 at 37°C. At regular time intervals (1, 2, 4, 6, 12, 24, 48, 72, and 96 h) was the measured quantity of released keratin from the hydrogels, 2 ml of the medium was withdrawn, replaced with the equivalent volume of fresh PBS and examined for the released keratin by the UV-VIS spectrophotometer (Shimadzu 1800, Japan) [24]. The keratin absorbance was read at λ 246 nm.…”