DOI: 10.14457/tu.the.2019.1630
title: Effect of beta-tricalcium phosphate nanoparticles on properties of thermosensitive chitosan/collagen hydrogel and control release of natural flavonoids

description: Thermosensitive hydrogel was developed to enable minimal invasive surgery and to address high demands for bone augmentation and regeneration in dental implant patients, particularly in an elderly. A concept behind the study was to incorporate an inorganic material in an organic matrix to create a hybrid matrix composing of beta tricalcium phosphate nanoparticles-chitosan/collagen matrix (bTCP-chitosan/collagen), and also employ natural bioactive molecules such as quercetin, to enhance biological function of the matrix. After that regulated sol-gel transformation of the hydrogel through physical crosslinking functions of betaglycerophosphate (bGP) and temperature change at a physiologic temperature and pH level. As a result, a thermosensitive bTCP-bGP-chitosan/collagen-quercetin hydrogel was fabricated. The study aimed to investigate effects of beta-tricalcium phosphate nanoparticles (bTCP) on microstructure, physicochemical, mechanical, physical and control release properties of the bTCP-bGP-chitosan/collagen hydrogel. Materials & methods: Different concentrations of bTCP 1, 2 and 3% (w/v) were incorporated in the bGP-2:1 (w/w) chitosan/collagen hydrogel on ice and then sol-gel transition of the matrix was activated by 14% (w/v) bGP and temperature change at 37°C. After that microstructure, physicochemical, mechanical, and physical properties of the hydrogels were characterized and compared. Subsequently 3% (w/v) bTCP was selected as an experimental group to investigate effects of bTCP on release profiles of quercetin from the bTCP-bGP-chitosan/collagen-quercetin hydrogel (n=3-5, Mean±SD). Results: It was found that pH values and gelation time were not affected by 1-3% (w/v) bTCP in the bGP-chitosan/collagen matrix. Microstructure analysis demonstrated that bTCP did not alter well defined porous structure with interconnected pores of the bGPchitosan/collagen matrix. Homogenous distribution of bTCP nanoparticles in the chitosan/collagen matrix was demonstrated by micro-computed tomography analysis (micro-CT), Scanning electron microscope (SEM) images and the increasing of calcium element in an energy-dispersive (EDS) analysis. Median pore sizes of the bTCP-bGPchitosan/collagen hydrogels were ranging from 100–200 µm and the hydrogels exhibited high porosity and permeability that were comparable to those of human cancellous bone. A higher concentration of bTCP (3% w/v) was associated with a decreasing of pore size, porosity, and permeability of the hydrogel. Referring to Fourier transform infrared spectroscopy (FT-IR) analysis, a shifting of the N-H bending vibration band (1541 cm−1) in atelocollagen spectrum to a higher frequency (1560 cm−1) in bGPbTCP-chitosan/collagen hydrogel analysis suggested a formation of intermolecular electrostatic attractions among bGP-chitosan/collagen composite matrix. Regarding mechanical and physical properties, bTCP increased mechanical strength and decreased degree of the swelling and the degradation rates of the hydrogels, particularly in a 3%bTCP group. After that based on microstructure, mechanical and physical properties of the hydrogel, 3% bTCP group was selected for a quercetin release study. The investigation demonstrated that the hydrogel with and without bTCP exhibited a sustain release pattern of the quercetin over a period of 7 days, while 3% bTCP slightly but significantly decreased releasing rate of the quercetin. Conclusion: the bTCP-bGP-chitosan/collagen hydrogels were thermosensitive, porous, and degradable in physiologic environment, and could function as a sustained release carrier of quercetin. An incorporation of bTCP improved mechanical and physical properties of the hydrogel while did not interfere with the formation of chitosan/collagen composite matrix. The 3% (w/v) bTCP-bGP-chitosan/collagen hydrogels were favourable thermosensitive hydrogels to support bone regeneration. Further studies should be conducted to further improve mechanical strength and gelation time of the hydrogel and to investigate biological property of the hydrogel in aspects of biocompatibility, cell encapsulation and bone formation capacity of the hydrogel.