Cellulose phosphates as biomaterials. II. Surface chemical modification of regenerated cellulose hydrogels

Abstract

ABSTRACT:Cellulose regenerated by the viscose process was previously investigated as an implantable material in orthopedic surgery. It was envisaged to take advantage not only of its good matching with mechanical properties of bone but also of its hydroexpansivity, therefore allowing a satisfactory fixation to hard tissue. Both the osteoconduction and the lack of osteoinduction of this material were demonstrated. Grafting of phosphate groups was then envisaged as the means to render cellulose more suitable for orthopedic applications by enhancing its bioactivity. In the present work, the previously optimized phosphorylation reaction was successfully adapted to the surface modification of regenerated cellulose. Modified materials were characterized by XPS, FTIR, and 31 P MAS NMR spectroscopic studies, and contact angle measurements, revealing the chemical bond between phosphate groups and cellulose, as well as the hydrophilic nature of phosphorylated materials, which increases with increasing phosphate contents. Water swelling and resistance to gamma sterilization were assessed as well, showing that phosphorylated materials swell considerably in water and were not affected when sterilization was carried out under a nitrogen atmosphere. The increase in surface roughness attributed to chemical modification was demonstrated through laser rugosimetry measurements.

Phosphorylation of bio-based compounds: the state of the art

“…The phosphorylation enhanced the cellulose surface bioactivity, helped the biomineralization and promoted bone regeneration for future orthopedic applications. [203][204][205][206] Carboxymethyl cellulose with one phosphate group for each disaccharide unit was used to functionalize titanium oxide surfaces and improved their osteointegration. 120 Similarly, Hydroxypropyl cellulose phosphorylated with polyphosphoric acid (DS = 1.3) demonstrates excellent adhesion onto metallic substrate and efficient corrosion inhibition capabilities, whereas cellulose derivatives without any surface-reactive groups do not build stable layers onto metal surfaces.…”

Preparation of a bonelike apatite–polymer fiber composite using a simple biomimetic process

“…Among the various coating techniques6–20 that can be used to form an apatite layer on a polymer surface, the biomimetic process6–14 is intrinsically suitable for the production of bonelike apatite. A conventional and typical biomimetic process6–11 is carried out using the following procedure. First, the polymer surface is modified with functional groups that are effective in inducing apatite nucleation.…”

“…Second, the surface‐modified polymer is immersed in a simulated body fluid (SBF)21 that has ion concentrations similar to those of human blood plasma. SiOH,6, 7 TiOH,8 COOH,9 PO 4 H 2 ,10 and SO 3 H11 functional groups have been tested, but the apatite‐forming ability of these functional groups is so weak that they require a long period to induce apatite formation in an SBF. Therefore, they may need to be combined with calcium ions6, 7, 9–11 or arranged in a certain structure8 to accelerate apatite formation in an SBF.…”

Biomimetic approaches with smart interfaces for bone regeneration

“…Surface phosphorylated poly(vinyl alcohol), PVA exhibited enhanced cytocompatibility in vitro in addition to substantial apatite coating [121]. Instead of urea-phosphoric acid method, Li et al [117] employed sodium hydroxide-phosphoric acid for phosphorylating bamboo while Granja et al [122] phosphorylated regenerated cellulose with the aid of phosphoric acid and triethyl phosphate. In another study, the authors presented an alternative way for surface phosphorylation illustrated with poly (hydroxyl ethyl methacrylate-co methyl methacrylate) for biomimetic growth of calcium phosphate [119], and the functionalized material was demonstrated to direct bone bonding and elicited new bone formation [118].…”

“…(Biomimetic mineralization conditions are provided in the ‘Materials and Methods’ section).

Fig. 3Biomimetic apatite coating formed on surface functionalized polymeric substrates ( a ): poly(methyl methacrylate) (ref: 121, with permission from Elsevier); ( b ):chitosan (ref: 120; with permission from Elsevier); ( c ): poly(vinyl alcohol) with permission from Elsevier (ref: 122); ( d ): poly(hydroxy ethyl methacrylate-co-methyl methacrylate); ( e ): high magnification image of ( d )

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