Abstract
Present research is a preliminary report on the novel pH-responsive micelles based on an amphiphilic brush copolymer P(PEGMA)-b-P(DMAEMA-co-CPLAMA) used as the promising drug carrier. The copolymer was synthesized using cholesteryl poly(l-lactic acid) methacrylate (CPLAMA), poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) with appropriate hydrophobic/hydrophilic ratios via atom transfer radical polymerization. The copolymer compositions were determined by 1H NMR. The synthesized copolymer self-assembled into nano-scale micelles capable of encapsulating hydrophobic model drug naproxen in their hydrophobic cores in aqueous solutions. pH sensitivity and self-assembly behaviors of copolymer were studied by UV–vis transmittance, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering. The results showed that the copolymer had high pH responsivity with a phase transition pH around pH 6.2. The critical micelle concentrations at pH 6.5 were found about 2.4 mg L−1. The stable and small micelles were obtained at pH 5.5–6.5. Upon increasing pH higher than 7, the single micelles further assembled into the micellar aggregates. TEM images of copolymer micelles showed that the micelles are spherical in shape with the mean diameter of 152 nm at pH 6.2. In vitro release study of naproxen-loaded micelles with about 44 % loading efficiency and 8 % loading capacity was performed using dialysis method in phosphate-buffered solution at 37 °C. Release study implied that the proposed brush copolymer could produce stable nano-carriers with controllable drug release at the target sites (pH 5.5–7).
Highlights
In recent decades, there has been increased awareness of the necessity for the development of drug delivery systems to improve the properties of therapeutic compounds, increasing its effectiveness, and decreasing its harmful side effects (Allen and Cullis 2004)
Present research is a preliminary report on the novel pH-responsive micelles based on an amphiphilic brush copolymer P(PEGMA)-b-P(DMAEMA-co-cholesteryl poly(L-lactic acid) methacrylate (CPLAMA)) used as the promising drug carrier
The synthesized copolymer self-assembled into nano-scale micelles capable of encapsulating hydrophobic model drug naproxen in their hydrophobic cores in aqueous solutions. pH sensitivity and self-assembly behaviors of copolymer were studied by UV–vis transmittance, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering
Summary
There has been increased awareness of the necessity for the development of drug delivery systems to improve the properties of therapeutic compounds, increasing its effectiveness, and decreasing its harmful side effects (Allen and Cullis 2004). Amphiphilic polymers are self-assembled in aqueous solution to minimize contact between water and hydrophobic blocks, and can contain hydrophobic drugs in the inner hydrophobic core (Geun-woo et al 2009). Drug delivery systems capable of releasing their payload in response to stimuli have drowned much attention in recent years, whether to target tissues, to reach specific intracellular locations, or to promote drug release. Polymeric micelles are nano-scopic constructs that possess core/shell architecture. They are obtained from the self-assembly of amphiphilic block copolymers in an
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