The colon is an area where both the local and systemic delivery
of drugs can take place. Colon-targeted drug delivery aims to limit
the release and absorption of an orally administered drug to the
colon to locally treat associated diseases, including irritable bowel
syndrome or Crohn’s disease. For successfully delivering the drug
to the colonic area (the targeted site), the drug has to be masked to
protect from microbial and pH gradient degradations and release of
the drug while passing through the stomach and intestine before
reaching the colon [3].
Drug delivery approaches using biodegradable polysaccharide
hydrogel beads as drug carriers have shown a prospective to potentiate the therapeutic efficiency of orally administered drugs by
allowing a decreased dose to achieve desired therapeutic effects
[4]. This advantage ultimately addresses the challenges related to
systemic side effects that are currently faced through conventionally
oral drug administration. Hydrogels possess several desirable properties that make them an excellent drug delivery vehicle. They
provide a three-dimensional network with a high water content
that can encapsulate hydrophilic drugs (water-soluble) and prevent
premature enzymatic degradation by obstructing the diffusion of
enzymes into the inner space of the spherical hydrogel bead
[5]. Additionally, the adjustable physical and degradation elements
of hydrogel beads enable control over the drug-releasing properties
under physiological conditions [6].
These potential drug carriers allow an improvement of drug
stability as well as efficacy and reduction of adverse drug effects by
enabling a sustained and controlled drug release locally within the
colon. The drug-releasing properties are subjected to the bead’s
polysaccharide formulation and drug loading efficiency. Therefore,
the release kinetics of the drugs from the polysaccharide beads are
limited to the conditions found in the colonic environment externally acting on the beads [7].
It is crucial that pH-sensitive polymers are used to fabricate the
beads so they can withstand different levels of pH at varying transit
times to only initiate their swelling dissolution in colon site-specific
pH. As shown in Fig. 1, considering that the orally administered
bead needs to travel through pH-varying environments in the
gastrointestinal tract, including an acidic stomach of pH 1–2, an
almost neutral small intestine with a pH ranging from pH 6.5–7.5,
and ultimately to a colon with a pH of 5.7–7.0 [4].
In fabricating polymer-based beads as drug delivery vehicles,
the choice of pH-sensitive polymer is the first important aspect. The
most cost-efficient, structurally degradable polymer for the
intended application should be considered. Some biodegradable
polymers require functionalization in order to adjust their hydrophilicity and resulting swelling properties to a maximum under the
conditions of the targeted site of drug delivery.
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Janarthanan Pushpamalar et al.
of drugs can take place. Colon-targeted drug delivery aims to limit
the release and absorption of an orally administered drug to the
colon to locally treat associated diseases, including irritable bowel
syndrome or Crohn’s disease. For successfully delivering the drug
to the colonic area (the targeted site), the drug has to be masked to
protect from microbial and pH gradient degradations and release of
the drug while passing through the stomach and intestine before
reaching the colon [3].
Drug delivery approaches using biodegradable polysaccharide
hydrogel beads as drug carriers have shown a prospective to potentiate the therapeutic efficiency of orally administered drugs by
allowing a decreased dose to achieve desired therapeutic effects
[4]. This advantage ultimately addresses the challenges related to
systemic side effects that are currently faced through conventionally
oral drug administration. Hydrogels possess several desirable properties that make them an excellent drug delivery vehicle. They
provide a three-dimensional network with a high water content
that can encapsulate hydrophilic drugs (water-soluble) and prevent
premature enzymatic degradation by obstructing the diffusion of
enzymes into the inner space of the spherical hydrogel bead
[5]. Additionally, the adjustable physical and degradation elements
of hydrogel beads enable control over the drug-releasing properties
under physiological conditions [6].
These potential drug carriers allow an improvement of drug
stability as well as efficacy and reduction of adverse drug effects by
enabling a sustained and controlled drug release locally within the
colon. The drug-releasing properties are subjected to the bead’s
polysaccharide formulation and drug loading efficiency. Therefore,
the release kinetics of the drugs from the polysaccharide beads are
limited to the conditions found in the colonic environment externally acting on the beads [7].
It is crucial that pH-sensitive polymers are used to fabricate the
beads so they can withstand different levels of pH at varying transit
times to only initiate their swelling dissolution in colon site-specific
pH. As shown in Fig. 1, considering that the orally administered
bead needs to travel through pH-varying environments in the
gastrointestinal tract, including an acidic stomach of pH 1–2, an
almost neutral small intestine with a pH ranging from pH 6.5–7.5,
and ultimately to a colon with a pH of 5.7–7.0 [4].
In fabricating polymer-based beads as drug delivery vehicles,
the choice of pH-sensitive polymer is the first important aspect. The
most cost-efficient, structurally degradable polymer for the
intended application should be considered. Some biodegradable
polymers require functionalization in order to adjust their hydrophilicity and resulting swelling properties to a maximum under the
conditions of the targeted site of drug delivery.
172
Janarthanan Pushpamalar et al.