Preparation, Characterization of Cellulose Acetate from Cotton Linter andEvaluation as a Sustained Release Excipient in Tablet Formulations
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Date
2021-11
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Addis Ababa University
Abstract
Cotton linter (CL) is a by-product of the garment industry that is good raw material for
cellulose preparation. The aim of this study was to extract and characterize native cellulose
and cellulose acetate (CA) from CL and evaluates CA as a sustained release excipient in
tablet formulation. In this study, cellulose was extracted by steam explosion method and CA
was prepared from the extracted cellulose by using acetic anhydride as acetylating agent and
sulphuric acid as a catalyst. Physico-chemical properties of cellulose and CA were
characterized. Mechanical properties of plain CA tablets and release profile of theophylline
as a model drug were investigated from CA matrix. The cellulose yield from CL on dry
weight basis was found to be 78.06%+1.70, while CA yield from cotton linter cellulose
(CLC) was 112.4%+1.28. The degree of polymerization (DP) of CLC was 472.52+3.64,
while DP of cotton linter cellulose acetate (CLCA) preparations ranged from 148.24+1.80 -
234.09+4.12 based on their degree of substitution (DS). The identification of CLCA was
confirmed by Fourier transform infrared (FTIR) spectra, while CLC was identified by using
chemical test in addition to FTIR. The degree of crystallinity of CLC was 81.59% and those
of CLCA with DS 0.83 and DS 2.46 were 57.92% and 33.78%, respectively. Scanning
electron microscopy (SEM) of CLC showed fibrous morphology while SEM of CLCA
revealed aggregated particles. The CLCA with DS 2.46 exhibited better heat stability than
CLC and comparable result with commercial cellulose acetate (CCA). However, CLC
exhibited better thermal stability than CLCA having DS 0.83. The CLCA with DS 2.46
exhibited good flow properties making it suitable for direct compression. The release study
showed that, matrix tablets of CLCA with DS 2.46 preparations exhibited prolonged
disintegration times and retarded in-vitro dissolution than tablets prepared with CLCA DS
0.83 and comparable result with CCA. However, CLCA had higher % release of drug as
compared to ethyl cellulose (EC) containing formulation. The drug release rate was also
prolonged as the percentage of CLCA DS 2.46 increased from 59.5% to 79.5% (w/w). The
kinetic study showed that, the formulations are best fitted to the Higuchiās square root kinetic
model (R
2
= 0.9862 to 0.9976) indicating the release of drug from the matrix was diffusion
based. Therefore, CL could be a potential local source of cellulose while CLCA could be a
potential candidate as a sustained release excipient.
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Keywords
Cellulose, Cellulose acetate, Cotton linter, Degree of substitution, Sustained release