hydrolysis of its ester linkages at physiological conditions. PCL has been considered for long-term drug or vaccine delivery devices. A contraceptive device known
as Capronor, composed of PCL, has been used for the controlled release of
levonorgestrel [139]. Due to the excellent biocompatibility of both pure PCL and
its composites, it has widely been used as scaffolds for tissue engineering [140].
The copolymer of E-caprolactone and glycolide results in less rigidity than
polymers of polyglycolide and has been developed as a drug delivery device
(SynBiosys). Poly(ethylene oxide) (PEO)-modified PCL nanoparticles prepared
by a solvent displacement method were used to embed tamoxifen in polymeric
nanoparticles, which gave significantly increased levels of accumulation of tamoxifen within the tumor [141]. Taxol-loaded PEG-PCL nanospheres have been
reported as having promising anticancer activity [142]. Nanoparticles prepared by
blending PCL and a polycationic nonbiodegradable acrylic polymer have been used
as a drug delivery carrier for oral administration of insulin, with entrapment
efficiency of around 96% [143], confirming the mucoadhesive properties of
polycationic polymers that allow the intestinal uptake of insulin [143]. Poly
(n-isopropylacrylamide)-b-poly(3-caprolactone) (PNPCL) block copolymers have
been used to encapsulate 70–90% of the hydrophobic drug clonezepam to enhance
the effect of GABA in brain [144]. Further, PCL nanoparticles have been developed
in order to study their ability to improve the anti-leishmanial action of
Amphotericin B (AmB), with concomitant reduction in the toxicity associated
with it [145].
6.5 Poly(alkyl cyanoacrylate)
Poly(alkyl cyanoacrylates) (PACs) are prepared through anionic polymerization of
alkyl cyanoacrylic monomers with a trace amount of moisture as the initiator. PAC
has been used to prepare excellent synthetic surgical glue, skin adhesive, and an
embolic material. PAC is one of the fastest degrading polymers, having degradation
times from a few hours to a few days depending on the length of the alkyl side
groups. The lower alkyl derivatives degrade within hours in an aqueous environment and release toxic degradation products such as cyanoacetic acid and formaldehyde. Most of the research in this area has therefore been concentrated on higher
alkyl derivatives such as octyl and isobutyl cyanoacrylates. PAC nanoparticles have
several advantages over other polymeric nanoparticles with their easy preparation,
high utility size ranges, absence of solvent residues, ability to form appropriate
nanoparticles, and ability to absorb or encapsulate a wide range of drug or protein
molecules. Nanoprecipitation has been adopted to prepare pure and drug-loaded
PAC nanoparticles for the entrapment of highly sensitive reactive drugs [146, 147].
Ampicillin-loaded poly(isohexyl cyanoacrylate) (PIHCA) nanoparticles have been
found to increase the antibiotic efficacy by 120-fold in experimental salmonellosis
[148]. Other antibiotics have also been incorporated into various PAC-based
nanocarriers [146, 149]. Ciprofloxacin-loaded PAC nanoparticles have been
188
S.K. Pandey et al.
as Capronor, composed of PCL, has been used for the controlled release of
levonorgestrel [139]. Due to the excellent biocompatibility of both pure PCL and
its composites, it has widely been used as scaffolds for tissue engineering [140].
The copolymer of E-caprolactone and glycolide results in less rigidity than
polymers of polyglycolide and has been developed as a drug delivery device
(SynBiosys). Poly(ethylene oxide) (PEO)-modified PCL nanoparticles prepared
by a solvent displacement method were used to embed tamoxifen in polymeric
nanoparticles, which gave significantly increased levels of accumulation of tamoxifen within the tumor [141]. Taxol-loaded PEG-PCL nanospheres have been
reported as having promising anticancer activity [142]. Nanoparticles prepared by
blending PCL and a polycationic nonbiodegradable acrylic polymer have been used
as a drug delivery carrier for oral administration of insulin, with entrapment
efficiency of around 96% [143], confirming the mucoadhesive properties of
polycationic polymers that allow the intestinal uptake of insulin [143]. Poly
(n-isopropylacrylamide)-b-poly(3-caprolactone) (PNPCL) block copolymers have
been used to encapsulate 70–90% of the hydrophobic drug clonezepam to enhance
the effect of GABA in brain [144]. Further, PCL nanoparticles have been developed
in order to study their ability to improve the anti-leishmanial action of
Amphotericin B (AmB), with concomitant reduction in the toxicity associated
with it [145].
6.5 Poly(alkyl cyanoacrylate)
Poly(alkyl cyanoacrylates) (PACs) are prepared through anionic polymerization of
alkyl cyanoacrylic monomers with a trace amount of moisture as the initiator. PAC
has been used to prepare excellent synthetic surgical glue, skin adhesive, and an
embolic material. PAC is one of the fastest degrading polymers, having degradation
times from a few hours to a few days depending on the length of the alkyl side
groups. The lower alkyl derivatives degrade within hours in an aqueous environment and release toxic degradation products such as cyanoacetic acid and formaldehyde. Most of the research in this area has therefore been concentrated on higher
alkyl derivatives such as octyl and isobutyl cyanoacrylates. PAC nanoparticles have
several advantages over other polymeric nanoparticles with their easy preparation,
high utility size ranges, absence of solvent residues, ability to form appropriate
nanoparticles, and ability to absorb or encapsulate a wide range of drug or protein
molecules. Nanoprecipitation has been adopted to prepare pure and drug-loaded
PAC nanoparticles for the entrapment of highly sensitive reactive drugs [146, 147].
Ampicillin-loaded poly(isohexyl cyanoacrylate) (PIHCA) nanoparticles have been
found to increase the antibiotic efficacy by 120-fold in experimental salmonellosis
[148]. Other antibiotics have also been incorporated into various PAC-based
nanocarriers [146, 149]. Ciprofloxacin-loaded PAC nanoparticles have been
188
S.K. Pandey et al.