Application of Nanotechnology in Diagnosis and Therapeutics
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antimicrobial drugs such as rifampicin, amphotericin B, and amoxicillin have been
extensively utilized for controlled and sustained release of drug to the targeted site
and increasing the patient compliance in infectious diseases (Dube et al. 2014; Jain
et al. 2014; Lin et al. 2013). Chitosan, nontoxic, low eye irritation, sustained release,
mucoadhesive, in situ gelling, transfection, and permeation enhancing properties aid
its application in ocular delivery of drugs such as indomethacin and pilocarpine. It
was observed that the drug level significantly increased in the anterior segment of
the eye and vitreous in relative to indomethacin eye drops. Pilocarpine formulations
showed increased sustained release and therapeutic efficacy (Calvo et al. 1996, 1997;
Kao et al. 2006; Lin et al. 2007).
3.2 Poly (Lactic-co-Glycolic Acid)
PLGA is a copolymer of lactic acid and glycolic acid, which is currently considered
as the best biomaterial for drug delivery. The poly-lactic acid and poly-glycolic acid
are basically synthesized in a fixed ratio (Makadia and Siegel 2011). It is synthesized
by ring-opening copolymerization of monomers, lactic acid, and glycolic acid via
ester linkages. PLGA are present in various forms, depending on the ratio of lactide and glycolide (PLGA (50:50) and PLGA (75:25)). Consequently, the ratio of
monomers affects the properties of the polymer. Low molecular weight of the polymer with high-glycolide content display more hydrophilicity, amorphous nature, and
less deterioration time. This can be attributed to the hydrophic nature of glycolide.
In contrast, polymer with high-lactide content shows more hydrophocity and higher
deterioration rate due to less water absorption (Danhier et al. 2012; Prokop and
Davidson 2008; Schliecker et al. 2003). Further, physical properties such as molecular weight, polydispersity index, T g, and degree of crystallinity have a profound effect
on swelling behavior, biodegradation rate, and mechanical strength of the polymer
(Siegel et al. 2006). The unique properties have allowed the polymer application
in drug delivery owing to its controlled drug release from weeks to months. The
hydrolysed products: lactic acid and glycolic acid are further metabolized into CO 2
and H 2 O via Krebs cycle. Thus, PLGA is a widely explored polymer for the purpose
of drug delivery (Acharya and Sahoo 2011).
In order to serve as a drug delivery vehicle, the polymeric NPs are required to
persist in systemic circulation for a prolonged duration. However, clearance of NPs
through reticuloendothelial system (RES) remains to be one of the most challenging
problems in the development of drug delivery system (Danhier et al. 2012; Kumari
et al. 2010). The clearance of NPs is mainly mediated by binding of opsonin proteins in the blood serum, where the particles are engulfed by phagocytosis. Thus,
despite all the beneficial properties, PLGA NPs are prone to renal clearance (Jain
et al. 2011). To overcome this trouble, the NPs are subjected to surface modification
using hydrophilic molecules to prevent rapid clearance from the body (Jeong et al.
2001). Hydrophilic polymeric nanoparticles have longer retention time in comparison to hydrophobic molecules. Therefore, PLGA were derivatized using hydrophilic
421
antimicrobial drugs such as rifampicin, amphotericin B, and amoxicillin have been
extensively utilized for controlled and sustained release of drug to the targeted site
and increasing the patient compliance in infectious diseases (Dube et al. 2014; Jain
et al. 2014; Lin et al. 2013). Chitosan, nontoxic, low eye irritation, sustained release,
mucoadhesive, in situ gelling, transfection, and permeation enhancing properties aid
its application in ocular delivery of drugs such as indomethacin and pilocarpine. It
was observed that the drug level significantly increased in the anterior segment of
the eye and vitreous in relative to indomethacin eye drops. Pilocarpine formulations
showed increased sustained release and therapeutic efficacy (Calvo et al. 1996, 1997;
Kao et al. 2006; Lin et al. 2007).
3.2 Poly (Lactic-co-Glycolic Acid)
PLGA is a copolymer of lactic acid and glycolic acid, which is currently considered
as the best biomaterial for drug delivery. The poly-lactic acid and poly-glycolic acid
are basically synthesized in a fixed ratio (Makadia and Siegel 2011). It is synthesized
by ring-opening copolymerization of monomers, lactic acid, and glycolic acid via
ester linkages. PLGA are present in various forms, depending on the ratio of lactide and glycolide (PLGA (50:50) and PLGA (75:25)). Consequently, the ratio of
monomers affects the properties of the polymer. Low molecular weight of the polymer with high-glycolide content display more hydrophilicity, amorphous nature, and
less deterioration time. This can be attributed to the hydrophic nature of glycolide.
In contrast, polymer with high-lactide content shows more hydrophocity and higher
deterioration rate due to less water absorption (Danhier et al. 2012; Prokop and
Davidson 2008; Schliecker et al. 2003). Further, physical properties such as molecular weight, polydispersity index, T g, and degree of crystallinity have a profound effect
on swelling behavior, biodegradation rate, and mechanical strength of the polymer
(Siegel et al. 2006). The unique properties have allowed the polymer application
in drug delivery owing to its controlled drug release from weeks to months. The
hydrolysed products: lactic acid and glycolic acid are further metabolized into CO 2
and H 2 O via Krebs cycle. Thus, PLGA is a widely explored polymer for the purpose
of drug delivery (Acharya and Sahoo 2011).
In order to serve as a drug delivery vehicle, the polymeric NPs are required to
persist in systemic circulation for a prolonged duration. However, clearance of NPs
through reticuloendothelial system (RES) remains to be one of the most challenging
problems in the development of drug delivery system (Danhier et al. 2012; Kumari
et al. 2010). The clearance of NPs is mainly mediated by binding of opsonin proteins in the blood serum, where the particles are engulfed by phagocytosis. Thus,
despite all the beneficial properties, PLGA NPs are prone to renal clearance (Jain
et al. 2011). To overcome this trouble, the NPs are subjected to surface modification
using hydrophilic molecules to prevent rapid clearance from the body (Jeong et al.
2001). Hydrophilic polymeric nanoparticles have longer retention time in comparison to hydrophobic molecules. Therefore, PLGA were derivatized using hydrophilic