Collagen–synthetic polymer interactions in solution and in thin films

doi:10.1016/j.molliq.2008.06.005

Journal of Molecular Liquids

Volume 145, Issue 3, 15 May 2009, Pages 135-138

https://doi.org/10.1016/j.molliq.2008.06.005 Get rights and content

Abstract

The miscibility of four different systems: collagen/poly(vinyl pyrrolidone) PVP, collagen/poly(ethylene oxide) PEO, collagen/poly(ethylene glycol) PEG and collagen/poly(vinyl alcohol) PVA has been studied by viscosimetry and by Fourier transform infrared spectroscopy (FTIR). It was found that collagen and PVP are miscible due to the strong interactions between the synthetic and biological component, mainly by hydrogen bonds. Moreover, it was found that collagen and PEO are immiscible as there is a lack of strong interactions between the synthetic and biological component. PEG and PVA were partially miscible with collagen. Blending of collagen with synthetic polymers gives the possibility of producing new materials for potential biomedical applications. However, biocompatibility of the new materials is worse than that for collagen.

Introduction

During the past two decades there has been great scientific and commercial progress in the area of polymer blends. According to the theory of Flory–Huggins the miscibility and compatibility of two polymers depend on their ability to form specific interaction between them, which contributes to diminish or make negative the mixing enthalpy. Blends of synthetic and natural polymers represent a new class of materials with better mechanical properties and biocompatibility than those of the single components [1]. Collagen is the most abundant biopolymer in animals where it provides the principal structural and mechanical support [2]. Collagen is readily available, non-toxic and provides an excellent basis for biomaterials [3], [4]. The main amino acids in collagen are: glycine, proline, hydroxyproline and alanine. The ordered triple helical structure of collagen is stabilized by both intrachain hydrogen bonds and by structural water molecules. Collagen is readily available, non-toxic and has the fibril architecture inherent in natural tissues.

The aim of this work was to study the interactions between collagen and selected synthetic polymers. As synthetic polymers poly(vinyl pyrrolidone) PVP, poly(ethylene oxide) PEO poly(ethylene glycol) PEG and poly(vinyl alcohol) PVA have been used. The chemical structure of synthetic polymers used in the investigations is presented in Scheme 1. PVP, PVA, PEO and PEG are water soluble polymers with a broad range of applications. Mainly they are used for biomedical applications. PVP is used for preparation of synthetic plasmas (substitute of plasma blood) and for preparation of thromboresistant hydrophilic gels in pharmacy and medicine. PVA is used as a sizing agent or stabilizer of dispersion systems. Due to solubility and biodegradability, PVA films are increasingly used also as packaging materials. PEO and PEG are simple chain polymers with etheric linkages. The above mentioned polymers are water soluble hydrophilic compounds. Blends of collagen and synthetic polymer have been prepared mainly in the form of films using the solution casting method. The interactions between two polymers and biological properties of the blends were investigated by FTIR, fluorescence and viscosimetry measurements. Biocompatibility of collagen and collagen/polymer blends has been compared.

Section snippets

Materials and methods

Collagen was obtained in our laboratory from tail tendons of young albino rats. Poly(vinyl pyrrolidone) PVP, poly(ethylene oxide) PEO, poly(ethylene glycol) PEG and poly(vinyl alcohol) PVA were purchased from Fluka. Polymeric blends were prepared by mixing of suitable volumes of collagen and other polymer aqueous solution. Polymer films were obtained by casting solution onto glass plate or CaF₂ specrophotometric windows. After solvent evaporation, the samples were dried in air at room

Results and discussion

According to the classical Huggins Eq. (1), from the intercept and slope of the plots of η_sp/c vs c, [η] and b_m (for solutions of individual polymers) are obtained. The values of b₂₃ are obtained by substituting all the terms in Eq. (4). Viscometric data for binary blends containing collagen and PVP shows that collagen and PVP are miscible. Similar results have been obtained for collagen/PVA blend [7]. The parameter Δb > 0 signifies the miscibility. Intrinsic viscosity for the blends is different

Conclusions

The FTIR and viscosimetry results show that collagen macromolecule could form different types of hydrogen bonds with synthetic polymer macromolecule. Hydrogen bonds can be formed between two hydroxyl groups (OH---OH) and/or between the amide group and oxygen of the hydroxyl group (NH---OH). Moreover, hydrogen bonds can be formed between the hydrogen of heteroatoms and the carbonyl group of the amide (C 6-point double bond O----HO, CO----HN). Interactions between two macromolecules depends on the presence of

Acknowledgments

Financial support from the Ministry of Science and Information Society Technologies (MNII, Poland) grant number 3T08E 3829, is gratefully acknowledged.

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