K. P. Chennazhi

Injectable Chitin-Poly(ε-caprolactone)/Nanohydroxyapatite Composite Microgels Prepared by Simple Regeneration Technique for Bone Tissue Engineering

Injectable gel systems, for the purpose of bone defect reconstruction, have many advantages, such as controlled flowability, adaptability to the defect site, and increased handling properties when compared to the conventionally used autologous graft, scaffolds, hydroxyapatite blocks, etc. In this work, nanohydroxyapatite (nHAp) incorporated chitin-poly(ε-caprolactone) (PCL) based injectable composite microgels has been developed by a simple regeneration technique for bone defect repair. The prepared microgel systems were characterized using scanning electron microscope (SEM), Fourier transformed infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The composite microgel, with the incorporation of nHAp, showed an increased elastic modulus and thermal stability and had shear-thinning behavior proving the injectability of the system. The protein adsorption, cytocompatibility, and migration of rabbit adipose derived mesenchymal stem cells (rASCs) were also studied. Chitin-PCL-nHAp microgel elicited an early osteogenic differentiation compared to control gel. The immunofluorescence studies confirmed the elevated expression of osteogenic-specific markers such as alkaline phosphatase, osteopontin, and osteocalcin in chitin-PCL-nHAp microgels. Thus, chitin-PCL-nHAp microgel could be a promising injectable system for regeneration of bone defects which are, even in deeper planes, irregularly shaped and complex in nature.

In vitro hemocompatibility and vascular endothelial cell functionality on titania nanostructures under static and dynamic conditions for improved coronary stenting applications

The usefulness of nanoscale topography in improving vascular response in vitro was established previously on hydrothermally modified titanium surfaces. To propose this strategy of surface modification for translation onto clinically used metallic stents, it is imperative that the surface should be also hemocompatible: an essential attribute for any blood-contacting device. The present in vitro study focuses on a detailed hemocompatibility evaluation of titania nanostructures created through an alkaline hydrothermal route on metallic Ti stent prototypes. Direct interactions of TiO2 nanocues of various morphologies with whole blood were studied under static conditions as well as using an in vitro circulation model mimicking arterial flow, with respect to a polished Ti control. Nanomodified stent surfaces upon contact with human blood showed negligible hemolysis under constant shear and static conditions. Coagulation profile testing indicated that surface roughness of nanomodified stents induced no alterations in the normal clotting times, with insignificant thrombus formation and minimal inflammatory reaction. Endothelialized nanomodified Ti surfaces were found to inhibit both activation as well as aggregation of platelets compared with the control surface, with the endothelium formed on the nanosurfaces having an increased expression of anti-thrombogenic genes. Such a nanotextured Ti surface, which is anti-thrombogenic and promotes endothelialization, would be a cost-effective alternative to drug-eluting stents or polymer-coated stents for overcoming in-stent restenosis.

Influence of titania nanotopography on human vascular cell functionality and its proliferation in vitro

Surface modification of metallic implants has been suggested as a viable means to alleviate the problems related to late stent restenosis. This work aims to develop an antithrombotic stent surface by appropriate nanosurface modification of biocompatible metallic titanium (Ti) to address these issues. An array of unique, integrated TiO2 nanostructures were developed on a metallic Ti surface using a simple aqueous chemistry technique. The influence of surface nanotopography on the proliferation and functionality of vascular endothelial and smooth muscles cells was investigated in vitro. All nanostructured samples showed significantly enhanced cellular viability and proliferation of endothelial cells, with raised levels of nitric oxide and substantially decreased smooth muscle cell proliferation and platelet adhesion in comparison to unmodified Ti. These beneficial effects suggest the potential use of such nanomodifications on metallic Ti as a suitable solution to reduce the probability of late stent thrombosis associated with bare metallic stents.

Biomedical Applications of Polymer/Silver Composite Nanofibers

Electrospinning is a very attractive method for preparing polymer or composite nanofibers. Electrospun nanofibers with a high surface area-to-volume ratio have received much attention because of their biomedical applications. Recently, the incorporation of metal nanoparticles into polymer nanofibers has drawn a great deal of attention because these metal nanoparticles can endow the polymer nanofibers with distinctive properties, such as optical, electronic, catalytic, and antimicrobial properties. These properties enable nanofibers to be used in variety of novel applications such as biosensors, catalysts, nanoelectronic devices, etc. Nanofibers containing silver nanoparticles have a wide range of application potential such as for filtration, wound dressings, tissue engineering, biosensors, and catalysts. This review summarizes the preparation and applications of silver nanoparticles incorporated into polymeric nanofibers.

In vitro and in vivo evaluation of osteoporosis therapeutic peptide PTH 1-34 loaded pegylated chitosan nanoparticles.

Oral formulation of human parathyroid hormone 1-34 (PTH 1-34) is an alternative patient compliant route in treating osteoporosis. PTH 1-34 loaded chitosan nanoparticles were PEGylated (PEG-CS-PTH NPs) and characterized by DLS, SEM, TEM and FTIR. PEG-CS-PTH NP aggregates of 200-250 nm which in turn comprised 20 nm individual nanoparticles were observed in SEM and TEM images respectively. The PEG-CS-PTH NP with 40% encapsulation efficiency was subjected to an in vitro release in simulated rat body fluids. PEG-CS-PTH NP treated human primary osteoblast cells, upon PTH 1-34 receptor activation, produced second messenger-cAMP, which downstream stimulated intracellular calcium uptake, production of bone specific alkaline phosphatase, osteocalcin etc., which substantiates the anabolic effect of the peptide. PEG-CS-PTH NPs showed an oral bioavailability of 100-160 pg/mL PTH 1-34 throughout 48 h, which is remarkable compared to the bare PTH 1-34 and CS-PTH NPs. The NIR image of gastrointestinal transit of ICG conjugated PEG-CS-PTH NPs supports this significant finding.