Reverse engineering of an anatomically equivalent nerve conduit

Reconstruction of peripheral nervous tissue remains challenging in critical-sized defects due to the lack of Büngner bands from the proximal to the distal nerve ends. Conventional nerve guides fail to bridge the large-sized defect owing to the formation of a thin fibrin cable. Hence, in the present study, an attempt was made to reverse engineer the intricate epi-, peri- and endo-neurial tissues using Fused Deposition Modeling based 3D printing. Bovine serum albumin protein nanoflowers (NF) exhibiting Viburnum opulus 'Roseum' morphology were ingrained into 3D printed constructs without affecting its secondary structure to enhance the axonal guidance from proximal to distal ends of denuded nerve ends. Scanning electron micrographs confirmed the uniform distribution of protein NF in 3D printed constructs. The PC-12 cells cultured on protein ingrained 3D printed scaffolds demonstrated cytocompatibility, improved cell adhesion and extended neuronal projections with significantly higher intensities of NF-200 and tubulin expressions. Further suture-free fixation designed in the current 3D printed construct aids facile implantation of printed conduits to the transected nerve ends. Hence the protein ingrained 3D printed construct would be a promising substitute to treat longer peripheral nerve defects as its structural equivalence of endo- and perineurial organization along with the ingrained protein NF promote the neuronal extension towards the distal ends by minimizing axonal dispersion.

pH-Responsive Polypeptide-Based Smart Nano-Carriers for Theranostic Applications

Smart nano-carriers have attained great significance in the biomedical field due to their versatile and interesting designs with different functionalities. The initial stages of the development of nanocarriers mainly focused on the guest loading efficiency, biocompatibility of the host and the circulation time. Later the requirements of less side effects with more efficacy arose by attributing targetability and stimuli-responsive characteristics to nano-carriers along with their bio- compatibility. Researchers are utilizing many stimuli-responsive polymers for the better release of the guest molecules at the targeted sites. Among these, pH-triggered release achieves increasing importance because of the pH variation in different organ and cancer cells of acidic pH. This specific feature is utilized to release the guest molecules more precisely in the targeted site by designing polymers having specific functionality with the pH dependent morphology change characteristics. In this review, we mainly concert on the pH-responsive polypeptides and some interesting nano-carrier designs for the effective theranostic applications. Also, emphasis is made on pharmaceutical application of the different nano-carriers with respect to the organ, tissue and cellular level pH environment.

pH-Responsive Polyethylene Glycol Monomethyl Ether-ε-Polylysine-G-Poly (Lactic Acid)-Based Nanoparticles as Protein Delivery Systems

The application of poly(lactic acid) for sustained protein delivery is restricted by the harsh pH inside carriers. In this study, we synthesized a pH-responsive comb-shaped block copolymer, polyethylene glycol monomethyl ether-ε-polylysine-g-poly (lactic acid) (PEP)to deliver protein (bovine serum albumin (BSA)). The PEP nanoparticles could automatically adjust the internal pH to a milder level, as shown by the quantitative ratio metric results. The circular dichroism spectra showed that proteins from the PEP nanoparticles were more stable than those from poly(lactic acid) nanoparticles. PEP nanoparticles could achieve sustained BSA release in both in vitro and in vivo experiments. Cytotoxicity results in HL-7702 cells suggested good cell compatibility of PEP carriers. Acute toxicity results showed that the PEP nanoparticles induced no toxic response in Kunming mice. Thus, PEP nanoparticles hold potential as efficient carriers for sustained protein release.