Preparation, Characterization and Evaluation of Cross-Linked Sweet Potato [Ipomoea batatas (L.) Lam.] Starch for Sustained Release Tablet Formulation
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Date
2023
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Addis Ababa University
Abstract
Along with cellulose and chitin, starch is one of the most prevalent biopolymers on earth and serves
as a significant reserve polysaccharide in higher plants. Starch is an important ingredient in many
products used in the food, pharmaceutical, and other industries. Despite its importance, starch is
rarely regarded as an ideal raw material because of its uncomplimentary properties. Thus,
modifications such as physical, chemical and enzymatically modifications are necessary to produce
starch derivatives with improved pharmaceutical properties. The aim of this study was to
chemically cross-link sweet potato (Ipomoea batatas (L.) Lam) starch using sodium
hexametaphosphate and evaluate its potential for sustained release applications.
Sweet potatoes (Ipomoea batatas (L. Lam)) starch was extracted, and then it was subjected to three
different concentrations (10%, 15% and 20%) of SHMP treatment to create cross-linked sweet
potato starches (CLSPSs): 10%-CLSPS, 15%-CLSPS, and 20%-CLSPS, at a temperature of 55°C,
and the cross-linking process took place for 8 hours. The degree of cross-linking for 10%-CLSPS,
15%-CLSPS, and 20%-CLSPS were 67.73% +1.86, 75.35% + 2.99, and 77.45% ± 0.34,
respectively. Increasing the concentration of sodium hexametaphosphate used for cross-linking
starch leads to higher degree of cross-linking, which in turn reduces the solubility and swelling
power of the starch. This is because the cross-linking process produces a more rigid and compact
structure, making it more difficult for water molecules to penetrate and interact with the starch
molecules. Moreover, in the moisture sorption study, it was observed that the water uptake capacity
of the starch decreased with an increase in cross-linking. Furthermore, the cross-linked starch
exhibited improved physical properties such as enhanced compressibility, powder density,
flowability, and heat stability as compared to its native starch. X-ray crystallography showed that
the CLSPSs had a crystal structure with a diffraction angle of 15.33°, 17.22°, and 22.96°, and nearly
the same crystallinity as the native starch. SEM photographs showed minor morphological
differences as it is observed on the powder surfaces of both native and CLSPS. The Fourier
Transform Infrared Spectroscopy and Differential scanning calorimetry investigations supported
the conclusion that there was no incompatibility between the model drug glibenclamide and CLSPS
polymer.
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Tablets were prepared using various amount of cross-linked starch by direct compression method
the prepared tablets were evaluated for the physical properties such as weight variation, thickness,
hardness, friability, disintegration time and in vitro drug release studies.
Preliminary studies result suggested the drug release characteristics from matrix tablets could be
influenced by the concentration of cross-linking agent, and the ratio of cross-linked starch.
Additionally, the suitability of methods used for determining these characteristics was also
assessed. According to the study's results, the prepared tablets had satisfactory physical properties
and met the standards. The tablets prepared with 10%-CLSPS showed a glibenclamide release
percentage of 88% at 6 hours, while the tablets made with 15%-CLSPS released 85% of the drug
at the same time. The tablets prepared with 20%-CLSPS released 81.2% of the drug close to 12
hours. The tablet matrix gelling capabilities of CLSPS, which created a gel-like network around the
drug particles and slowed the rate of drug release, were thought to be responsible for the sustained-
release properties of the tablets. The Higuchi's model and the Kors meyer Peppa's models were
determined to best fit in-vitro dissolution data after being subjected to numerous drug release
kinetics models. It was identified that the "n" value for the diffusional release exponent, which
indicates that drug release processes involved both polymer erosion and diffusion, ranged between
0.6303 and 0.7367. The drug release pathways were consequently categorized as anomalous or non-
Fickian diffusion. In conclusion, the study findings suggest that cross-linked sweet potato starch is
a more favorable option for utilization in pharmaceutical formulations due to its superior sustained-
release properties. Therefore, it can be considered as a viable substitute polymer for achieving
sustained-release effects.
Description
Keywords
Cross-linked Starch, Glibenclamide, Matrix tablet, Sodium hexametaphosphate, Starch, Sweet potato (ipomoea batatas (L). Lam), Sustained release.