Molecular imprinting of proteins remains a huge challenge because of two major obstacles: difficulty in template removal and low imprinting efficiency. Herein, we propose a new strategy to simultaneously overcome these two challenges by creating molecularly imprinted polymers (MIPs) with nanoscale shape-memorable imprint cavities. These novel MIPs were developed by simply cross-linking the polymers with a peptide cross-linker instead of commonly used cross-linkers. Due to the unique pH-induced helixcoil transition of the peptide cross-linker, adjusting the pH from 5.5 to 7.4 leads to an expansion of the imprint cavities, thus facilitating template removal. Returning the pH back to 5.5 restores the original size and shape of the imprint cavities due to the precise refolding of peptide. A template protein can therefore be readily removed under mild conditions, while simultaneously achieving a significantly improved imprinting effect.

A facile method to tune the phase transition temperature of thermosensitive polymers is to introduce an additive; however, the influence of additives is usually limited. Here the influence of poly­(vinyl alcohol) (PVA), a polymeric additive, on thermal behavior of copolymers of acrylamide (AAm), N,N-dimethyl­acrylamide (DMAA), and 3-(acrylamido)­phenyl­boronic acid (3-AAPBA), P­(AAm-DMAA-3-AAPBA), was studied. With increasing AAm content, the phase transition temperature of the copolymers increases gradually. They finally become nonthermosensitive when AAm content exceeds 20 mol %. To study the influence of PVA on the copolymers, they were incorporated into thin films via layer-by-layer (LBL) assembly, using phenylboronate ester bonds between them as a driving force. Because the two polymers in the films were drawn very close to each other, the ability of PVA to depress phase transition temperature of copolymer is significantly amplified. As a result, an unprecedented large depression on phase transition temperature was observed. As an example, the phase transition temperature of P­(AAm-DMAA-3-AAPBA)15 is significantly decreased from 86 °C in solution to 14 °C in the LBL film, corresponding to a 72 °C decrease. More importantly, some copolymers that do not exhibit thermosensitive behaviors in solution can be turned to be thermosensitive, as their phase transition temperature can be decreased from ≥100 to <100 °C due to the extraordinarily large ability of PVA to depress the phase transition temperature. Consequently, films from these nonthermosensitive copolymers also present a heat-induced phase transition.

No abstract

The development of environmentally responsive drug delivery systems for the treatment of cancer has attracted particular interest in recent years. However, the enhancement of drug loading capacity and realization of pH-responsive drug delivery remain challenging. Herein, we employ carboxymethyl curdlan as a hydrophilic carrier to wrap doxorubicin (DOX) directly via electrostatic interaction. The sizes of the formed nanoparticles can be simply tuned by changing their feeding ratios. In particular, the nanoparticles are highly stable in aqueous solution without size variation. In vitro drug release and cytotoxicity assays illustrate that this delivery system can release DOX differentially under various environmental conditions and transport it into cell nuclei efficiently, with comparable therapeutic effect to the free drug. These results suggest that the carrying of antitumor drugs by polysaccharide via electrostatic interaction is a simple but effective way to construct a pH-dependent drug delivery platform.

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