Syed I. Ali

Polymer Encapsulated Gibbsite Nanoparticles: Efficient Preparation of Anisotropic Composite Latex Particles by RAFT-Based Starved Feed Emulsion Polymerization

Anisotropic polymer-inorganic composite latex particles were synthesized by using a RAFT-based encapsulation approach on cationic gibbsite platelets. By using the RAFT agent dibenzyl trithiocarbonate, a series of amphipatic living random RAFT copolymers with different combinations of acrylic acid and butyl acrylate units were synthesized. These RAFT copolymers were used as living stabilizers for the gibbsite platelets and chain extended to form a polymeric shell by starved feed emulsion polymerization. Cryo-TEM characterization of the resulting composite latexes demonstrates the formation of anisotropic composite latex particles with mostly one platelet per particle. Monomer feed composition, chain length, and hydrophilic-lipophilic balance of the RAFT copolymer were found to be important factors for the overall efficiency of the encapsulation. Good control over platelet orientation and high encapsulation efficiency were achieved via this route.

Polypeptide core-shell silica nanoparticles with high grafting density by N-carboxyanhydride (NCA) ring opening polymerization as responsive materials and for bioconjugation

Silica nanoparticles were furnished with a functional polypeptide shell to create a pH-responsive inorganic–organic hybrid material. Free amine groups present on silica nanoparticles initiated the N-carboxyanhydride (NCA) polymerization of particular amino acid NCAs directly onto the inorganic support, offering a convenient method to functionalize silica core nanoparticles with a uniformly dense polypeptide shell. Poly(γ-benzyl-L-glutamate) (PBLG), poly(e-carbobenzyoxy-L-lysine) (PZLL), and S-tert-butyl protected polycysteine (PtBLC) were grafted from the silica core both independently as homopolypeptides and simultaneously to form a copolypeptide shell, highlighting the versatility that the grafting mechanism possesses. The grafting of PBLG was investigated in detail at 0 °C and 20 °C to determine any differences in the size and uniformity of the polypeptide shell formed. Dynamic light scattering (DLS) analysis revealed a correlation between the thickness of the uniform organic shell and the amount of amino acid in the monomer feed, with higher linearity at the lower polymerization temperature. Size Exclusion Chromatography (SEC) analyses of degrafted PBLG confirmed the DLS results. A high grafting density of around 0.4 PBLG chains per nm2 was calculated highlighting the control afforded in this approach to polypeptide grafting. Subsequent deprotection of the PBLG homopolypeptide shell afforded pH-sensitive poly(glutamic acid) (PGA) coupled silica nanoparticles. The selective release of a model rhodamine B dye was demonstrated to emphasize the potential that these hybrid nanomaterials have for the on-demand release of payload molecules in response to a targeted pH trigger. Moreover, covalent bioconjugation was successfully shown by attachment of green fluorescent protein.

Vesicle-templated pH-responsive polymeric nanocapsules

We report the synthesis of pH responsive polymeric nanocapsules by templating unilamellar vesicles of dimethyldioctadecylammonium bromide (DODAB) using a RAFT-based templating approach. A short-chain living anionic copolymer containing randomly distributed acrylic acid and butyl acrylate units was first synthesized by RAFT in solution using dibenzyl trithiocarbonate (DBTTC) as the RAFT agent. The anionic copolymer chains were subsequently adsorbed onto the surface of cationic DODAB vesicles and were further chain extended to form a thick polymeric shell by feeding a monomer mixture comprising methyl methacrylate (MMA) and tertiary butyl acrylate (t-BA) in combination with the divinyl crosslinker ethylene glycol dimethacrylate (EGDMA) under starved feed conditions. CryoTEM characterization demonstrated successful formation of a thick crosslinked polymeric shell around the vesicles. Subsequent acid hydrolysis of the tertiary butyl ester groups of the crosslinked polymeric shell resulted in the formation of pH-responsive nanocapsules.

Controlled synthesis of polymeric nanocapsules by RAFT-based vesicle templating

Polymeric nanocapsules were synthesized by encapsulating extruded vesicles of dimethyldioctadecyl ammonium bromide (DODAB) using a reversible addition-fragmentation chain transfer (RAFT)-based encapsulation approach. Random copolymers containing acrylic acid and butyl acrylate units were first synthesized by RAFT in solution using dibenzyl trithiocarbonate (DBTTC) as the RAFT agent. These anionic copolymer chains were subsequently adsorbed onto the surface of cationic DODAB vesicles and then chain extended to form a polymeric shell by starved feed emulsion polymerization. Cryogenic transmission electron microscopy (cryo-TEM) characterizations demonstrate the successful formation of nanocapsules.

Исследование in vitro высвобождения капреомицина сульфата из полиэтилцианоакрилатных наночастиц

Показаны перспективы применения полиэтилцианоакрилата в качестве носителя противотуберкулезного препарата Капреомицина сульфата. Исследованы in vitro высвобождение Капреомицина сульфата из полиэтилцианоакрилатных наночастиц и деградация полимера.

Controlled release of Capreomycin sulphate from pH-responsive nanocapsules

Abstract The synthesis of polymeric nanocapsules loaded with the antituberculosis drug Capreomycin sulphate is presented in this work. The pHresponsive polymeric nanocapsules were successfully synthesized using the RAFT-based vesicle templating approach in the presence of Capreomycin sulphate. Anionic small polyelectrolytes comprising randomly distributed butyl acrylate and acrylic acid units were adsorbed on cationic vesicles of dimethyldioctadecyl ammonium bromide (DODAB). N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) or tertiary butyl methacrylate (tBMA) and MMA were used for the formation of the polymeric shells. Subsequently the tBMA was hydrolyzed to obtain negatively charged nanocapsules. The nanocapsule morphology for both approaches was characterized by DLS and TEM. The most stable hollow latex particles were obtained with the monomer composition of DMAEMA:MMA = 1:1. These nanocapsules were found to be colloidally stable and pH-responsive. The entrapment efficiency of drug determined by UV-Vis-spectroscopy was 70 %. The drug release rate from nanocapsules at pH 6.5 was found to be relatively fast (substantial release within one hour already), however we believe slower release can be achieved by using a thicker polymer shell.

Синтез и характеристика полиэтилцианоакрилатных наночастиц, иммобилизованных сульфатом капреомицина

Some aspects of the synthesis and characterization of polyethyl cyanoacrylate nanoparticles loaded with antituberculosis drug Capreomycin sulfate are considered in this work. Polyethyl cyanoacrylate nanoparticles containing Capreomycin sulfate have been synthesized using anionic polymerization in emulsion. Optimum conditions of immobilization of the drug into polymeric matrix have been found out. It was determined that to increase loading efficiency of the drug it has to be added into reaction medium after polymerization started.