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Triggered Release (triggered + release)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Chitosan Hydrogel-Capped Porous SiO2 as a pH Responsive Nano-Valve for Triggered Release of Insulin

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2009
Jianmin Wu
Abstract A pH responsive, chitosan-based hydrogel film is used to cap the pores of a porous SiO2 layer. The porous SiO2 layer is prepared by thermal oxidation of an electrochemically etched Si wafer, and the hydrogel film is prepared by reaction of chitosan with glycidoxypropyltrimethoxysilane (GPTMS). Optical reflectivity spectroscopy and scanning electron microscopy (SEM) confirm that the bio-polymer only partially infiltrates the porous SiO2 film, generating a double layer structure. The optical reflectivity spectrum displays Fabry,Pérot interference fringes characteristic of a double layer, which is characterized using reflective interferometric Fourier transform spectroscopy (RIFTS). Monitoring the position of the RIFTS peak corresponding to the hydrogel layer allows direct, real-time observation of the reversible volume phase transition of the hydrogel upon cycling of pH in the range 6.0,7.4. The swelling ratio and response time are controlled by the relative amount of GPTMS in the hydrogel. The pH-dependent volume phase transition can be used to release insulin trapped in the porous SiO2 layer underneath the hydrogel film. At pH 7.4, the gel in the top layer effectively blocks insulin release, while at pH 6.0 insulin penetrates the swollen hydrogel layer, resulting in a steady release into solution. [source]

Reduction-Sensitive Reversibly Crosslinked Biodegradable Micelles for Triggered Release of Doxorubicin

MACROMOLECULAR BIOSCIENCE, Issue 12 2009
Yanmin Xu
Abstract Reduction-responsive reversibly crosslinked biodegradable micelles were developed and applied for triggered release of doxorubicin (DOX). An amphiphilic block copolymer of poly(ethylene glycol) (PEG) and poly(, -caprolactone) (PCL) that contains two lipoyl functional groups at their interface (PEG-L2 -PCL) has been synthesized. 1H NMR spectroscopy and gel permeation chromatography (GPC) measurements show that the PEG-L2 -PCL block copolymer had a controlled composition (PEG 5 kDa and PCL 5.4 kDa) and a polydispersity index (PDI) of 1.36. PEG-L2 -PCL formed micelles with sizes that ranged from 20 to 150,nm in aqueous solutions, wherein a critical micelle concentration (CMC) of 16,mg·L,1 was determined. The micelles were readily crosslinked by adding 7.6,mol % of dithiothreitol (DTT) relative to the lipoyl groups. Notably, micelles after crosslinking demonstrated a markedly enhanced stability against dilution, physiological salt concentration, and organic solvent. In the presence of 10,×,10,3,M DTT, however, micelles were subject to rapid de-crosslinking. In vitro release studies showed minimal release of DOX from crosslinked micelles at a concentration of 10,mg,L,1 (C,<,CMC, analogous to intravenous injection), wherein less than 15% of the DOX was released in 10,h. In contrast, rapid release of DOX was observed for DOX-loaded non-crosslinked micelles under otherwise the same conditions (,80% release in 0.5,h). In the presence of 10,×,10,3,M DTT mimicking an intracellular reductive environment, sustained release of DOX from crosslinked micelles was achieved, in which 75% of the DOX was released in 9,h. These novel reduction-sensitive reversibly crosslinked biodegradable micelles are highly promising for targeted intracellular delivery of anticancer drugs. [source]

Design of Multiresponsive Hydrogel Particles and Assemblies

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
Grant R. Hendrickson
Abstract In the realm of soft nanotechnology, hydrogel micro- and nanoparticles represent a versatile class of responsive materials. Over the last decade, our group has investigated the synthesis and physicochemical properties of a variety of synthetic hydrogel particles. From these efforts, several particle types have emerged with potentially enabling features for biological applications, including nanogels for targeted drug delivery, microlenses for biosensing, and coatings for biomedical devices. For example, core/shell nanogels have been used to encapsulate and deliver small interfering RNA to ovarian cancer cells; nanogels used in this fashion may improve therapeutic outcomes for a variety of macromolecular therapeutics. Microgels arranged as multilayers on implantable biomaterials greatly minimize the host inflammatory response to the material. Furthermore, the triggered release of drugs (i.e., insulin) has been demonstrated from similar assemblies. The goal of this feature article is to highlight developments in the design of responsive microgels and nanogels in the context of our recent efforts and in relation to the community that has grown up around this fascinating class of materials. [source]