Cellulose phosphates as biomaterials. I. Synthesis and characterization of highly phosphorylated cellulose gels

Abstract

ABSTRACT:The present study concerns the investigation of a material expected to be biocompatible and able to promote bone regeneration. For this purpose, cellulose was chemically modified by phosphorylation. Once implanted, phosphorylated cellulose could promote the formation of calcium phosphates, thus having closer resemblance to bone functionality. In a previous investigation, the obtention and the preliminary characterization of cellulose phosphate gels were reported. In the present study, the synthesis by the H 3 PO 4 /P 2 O 5 /Et 3 PO 4 /hexanol method was optimized in terms of reaction parameters. The structure of materials was investigated by FTIR, Raman, and solid-state 31 P-and 13 C-NMR spectroscopic studies, and X-ray diffraction. Water swelling and stability to sterilization by gamma-radiation were also assessed. It was demonstrated that the present method allows highly phosphorylated cellulose derivatives to be obtained. Cellulose triphosphates gels are described here for the first time. Products obtained were poorly crystallized monoesters, apparently not significantly affected by gamma sterilization and showed a high water swelling capability. Chemical bonding was confirmed by FTIR, Raman, and both 31 P-and 13 C-NMR spectroscopies. It was also shown that the H 3 PO 4 / P 2 O 5 /Et 3 PO 4 /hexanol method provides a versatile and interesting alternative route to some of the more widely used techniques for the phosphorylation of cellulose.

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

“…58 It is worth to note that concerning the previous reactions, only quite low degrees of phosphorylation were obtained (less than 1.2). Granja et al 17 78,79 or in butanol by Amaral et al. 80 High substitution degrees up to 1.9 were obtained with chitin, which increased the solubility properties in aqueous media and in organic solvents.…”

“…The combined use of P 2 O 5 and H 3 PO 4 , allows obtaining highly phosphorylated sugar derivatives. 17 Phosphorus oxychloride, dialkyl chlorophosphonates or diphenylphosphinic chloride are the most employed phosphorylating agents for OH-containing organic compounds, this reaction is a derivate of Williamson reaction (Scheme 1C). The use of POCl 3 was first proposed in 1857.…”

Phosphated Cellulose as an Efficient Biomaterial for Aqueous Drug Ranitidine Removal

“…The increase intensity in the 1125–985 cm −1 region in the spectra for both chemically modified celluloses is a clear indication of the presence of phosphate group in the new synthesized biopolymers. The IR spectroscopy is not an equivocal technique for this investigation to conclude about the chemical modification of cellulose structure since the typical bands of phosphates are usually most pronounced in the area of the spectrum where the pulp already has several intense bands in the 900–1200 cm −1 interval [17,18,19,20,21]. …”

Esterification of Polysaccharides

“…Phosphorylation of cellulose can be achieved by heat treatment of a mixture of cellulose/urea/H 3 PO 4 at 150 • C [353]. A mixture of H 3 PO 4 , P 2 O 5 and (C 2 H 5 O) 3 PO in hexanol yields a cellulose phosphate gel (maximum DS 2.5) that is expected to promote calcium phosphate formation during bone regeneration [354].…”