Chemistry Reference
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material because of its annual availability from many plants, its rather excessive pro-
duction with regard to current needs and its low cost. It is known to be completely
degradable in soil and water and can promote the biodegradability of a non-biodegrad-
able plastic when blended. Starch is commonly pretreated with a plasticizer to make it
thermoplastic thus enabling melt-processing. However, TPS alone often cannot meet
all the requirements of a packaging material and an environmentally acceptable filler
is called for to improve theproperties of TPS in such applications. Clay is a potential
filler; itself a naturally abundant mineral that is toxin-free and can be used as one of
the components for food, medical, cosmetic, and healthcare recipients. TPS reinforced
by clay has recently been investigated. To the authors' knowledge, there are just four
publications describing this new class of materials, that is TPS-clay nanocomposites.
Starch is hydrophilic and forms nanocomposites with natural smectite clays and con-
ventional composites with kaolinite. It has been shown that the tensile strength of TPS
was increased from 2.6 to 3.3 MPa with the presence of 5 wt% sodium montmoril-
lonite, while the elongation at break was increased from 47 to 57%. Also the relative
water vapor diffusion coefficient of TPS was decreased to 65% and the temperature at
which the composite lost 50% mass was increased from 305 to 336°C.
Synthesis and Characterization of Chitosan-carboxymethyl Starch Hydrogels
as Nano Carriers for Colon-specific Drug Delivery
Although, colon delivery has become a widely accepted route of administration of
therapeutic drugs, the gastrointestinal tract presents several formidable barriers to drug
delivery. Colonic drug delivery has gained increased importance not just for the de-
livery of the drugs for the treatment of local diseases associated with the colon but
also for its potential for the delivery of proteins and therapeutic peptides. To achieve
successful colonic delivery, a drug needs to be protected from absorption and/or the
environment of the upper gastrointestinal tract (GIT) and then be abruptly released
into the proximal colon, which is considered the optimum site for colon targeted deliv-
ery of drugs. Colon targeting is naturally of value for the topical treatment of diseases
of colon such as Chron's diseases, ulcerative colitis, colorectal cancer, and amebiasis.
Peptides, proteins, oligonucleotides, and vaccines pose potential candidature for colon
targeted drug delivery. The novel intestinal specific drug delivery system with pH-sen-
sitive swelling and drug release properties was developed. The pH-sensitive hydrogel
containing ibuprofen pendents was used as colon-specific drug delivery. The carboxyl
group of ibuprofen was converted to a vinyl ester group by reacting ibuprofen and vi-
nyl acetate as an acylating agent in the presence of catalyst. The glucose-6-acrylate-1,
2, 3, 4-tetraacetate (GATA) monomer was prepared under mild conditions. Cubane-1,
4-dicarboxylic acid (CDA) linked to two 2-hydroxyethyl methacrylate (HEMA) group
was used as the cross-linking agent (CA). The goal of oral insulin delivery devices
is to protect the sensitive drug from proteolytic degradation in the stomach and up-
per portion of the small intestine. pH-responsive, poly(methacrylic
g
-ethylene glycol)
hydrogels are as oral delivery vehicles for insulin. Insulin was loaded into polymeric
microspheres and administered orally to healthy and diabetic Wistar rats.
In the acidic environment of the stomach, the gels were unswollen due to the for-
mation of intermolecular polymer complexes. The insulin remained in the gel and
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