Modification of Collagen Derivatives with Water-Soluble Polymers for the Development of Cross-Linked Hydrogels for Controlled Release

Abstract

Novel cross-linked hydrogels were synthesized as potential materials for the development of smart biofertilizers. For this purpose, hydrogels were prepared using collagen hydrolysate recovered from tannery waste. The water-soluble polymer poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMAx)) was among others used for the cross-linking reaction that combined hydrophilic nature with epoxide groups. The synthetic procedure was thoroughly investigated in order to ensure high percentage of epoxide groups in combination with water-soluble behavior. The copolymer did not show cytotoxicity against normal lung, skin fibroblasts, or nasal polyps fibroblasts. Through the present work, we also present the ability to control the properties of cross-linked hydrogels by altering copolymer’s composition and cross-linking parameters (curing temperature and time). Hydrogels were then studied in terms of water-uptake capacity for a period up to six days. The techniques Proton Nuclear Magnetic Resonance (1H NMR), Thermogravimetric Analysis (TGA), Size Exclusion Chromatography (SEC), and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) were applied for the characterization of the synthesized copolymers and the cross-linked hydrogels. Three samples of biofertilizers based on collagen hydrolysate functionalized with P(SSNa-co-GMAx) and starch and having nutrients encapsulated (N, P, K) were prepared and characterized by physical–chemical analysis and Energy Dispersive X-ray analysis-Scanning Electron Microscope (EDAX-SEM) in terms of microstructure. Preliminary tests for application as fertilizers were performed including the release degree of oxidable organic compounds.

Collagen-Based Hydrogels Composites from Hide Waste to Produce Smart Fertilizers

“…As referring to the release mechanism one may suppose that in the first stage, the organic and inorganic compounds with high solubility are removed, such as: peptides with short chains, soluble polymers (starch), amino acids, glucides (mono- and di-saccharides), nitrate salts, acids, etc. In the second stage the rate of release of oxidable compounds decreases for all fertilizers; this can be assessed to organic compounds with low solubility, such as proteins, collagen, and degradable polymers [ 12 ].…”

“…Release of oxidable compounds (organic and inorganic) in water from the tested agro-hydrogels has been characterized by their stepwise decomposition in aqueous medium in dynamic conditions, monitored by determination of chemical oxygen demand (CODMn) [ 12 ].…”

“…Release degree of oxidable compounds in water. The release degree of oxidable compounds (organic and inorganic) in the presence of KMnO 4 (CODMn) of all bio-fertilizers tested reflects their stepwise decomposition in aqueous medium in dynamic conditions, according to the method described in a previous paper [ 12 ].…”

“…In order to optimize the collagen hydrolysate encapsulation, reactive copolymers with various epoxide groups content were also synthesized and tested. Thus a thorough research in terms of optimization of the synthesis of the water soluble copolymer poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMAx)) was previously conducted, where x = 2, 5, 20, 30, and 40% mole GMA [12]. Example 3.…”

“…The hydrolyzed collagen represents a high solubility product that could be used in the food industry as a food supplement or in the cosmetic industry for skin care products [ 10 , 11 ]. By functionalization of collagen hydrolysate with encapsulated nutrients a product with application as a biofertilizer could be obtained [ 12 ]. Collagen hydrolysate added to synthetic polymers could improve the biodegradability of plastic materials [ 13 ], and collagen-based matrices could also be successfully cross-linked in order to modify mechanical properties or biodegradation rates [ 14 ].…”