Tunable Fluorescence from a Responsive Hyperbranched Polymer with Spatially Arranged Fluorophore Arrays.

In the present study, a water-soluble hyperbranched polymer platform that contained a Förster resonance energy transfer (FRET) array and exhibited varied fluorescence in response to solvent, light, and CN- anion stimuli was constructed. The use of chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization (CuAACP) enabled accurate control of the ratio and distance of three incorporated fluorophores, coumarin (Cou), nitrobenzoxadiazole (NBD), and photoswitchable spiropyran (SP), that could be reversibly transformed into the red-emitting merocyanine (MC) state. Within the FRET system, the energy flow from Cou to MC was significantly enhanced by the introduction of NBD as a central fluorophore relay. Moreover, the energy-transfer efficiency was increased by changing the solvent from tetrahydrofuran to more polar water; this was accompanied by a clear color change and fluorescence behavior. These correlations of polymer composition and solvent polarity to the FRET efficiency were finally applied to the effective detection of CN- anion; thus demonstrating a function of this polymer as a CN- sensor.

Tandem Functionalization in a Highly Branched Polymer with Layered Structure.

A hyperbranched polymer with multilayer structure was developed to demonstrate the possibility of highly efficient tandem functionalization reactions at different domains within one nanostructured platform. The polymer scaffold was constructed by chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization of three functional monomers with sequential monomer addition in one pot. Subsequent reactions with different monomer units resulted in efficient functionalization of each segment with construction of a highly sophisticated polymer structure by a robust procedure. As a proof of concept, the ability of this polymer structure to quantitatively load six species of guest molecules through three different types of conjugation reactions was demonstrated.

Preparation and characterization of double macromolecular network (DMMN) hydrogels based on hyaluronan and high molecular weight poly(ethylene glycol).

Abundant research efforts have been devoted to meet the demands for high-strength hydrogels in biomedical applications. Double-network (DN) hydrogels and homogeneous hydrogels are two typical samples. In this study, a novel ultra-strong and resilient double macromolecular network (DMMN) hydrogel system has been developed via a two-step sequential cross-linking process using hyaluronan (HA) and high molecular weight poly(ethylene glycol) (PEG) for the first and second network, respectively. A lower concentration of the HA precursor solution and a higher concentration of the PEG precursor solution as well as a higher molecular weight of the PEG precursor are beneficial to produce high-strength DMMN gels. Dynamic light scattering measurements demonstrate that DMMN gels possess the more evenly distributed polymer networks; the distinctive double and relatively evenly distributed networks of the DMMN gel make it combine the current DN and homogeneous network strategies for preparing robust hydrogels. The optimized DMMN gel is capable of sustaining up to 50 MPa of compressive stress. Besides, DMMN gels exhibit excellent cytocompatibility. This study expands the DN principle in designing and fabricating high-strength hydrogels with biocompatible macromolecules that show a promising prospect for biomedical applications.

Self-assembled micelles based on hydrophobically modified quaternized cellulose for drug delivery.

Novel amphiphilic cationic cellulose (HMQC) derivatives carrying long chain alkyl groups as hydrophobic moieties and quaternary ammonium groups as hydrophilic moieties were synthesized. Structure and properties of the amphiphilic cellulose derivatives were characterized by elemental analysis, FT-IR, (1)H NMR, ζ-potential measurement, dynamic light scattering (DLS), fluorescence spectroscopy and transmission electron microscopy (TEM). The results revealed that HMQCs can be self-assembled into cationic micelles in distilled water with the average hydrodynamic radius of 320-430 nm. The cytotoxicity study showed that the HMQC exhibited low cytotoxicity. Prednisone acetate, a water insoluble anti-inflammation drug, was chosen as a model drug to investigate the utilization of self-assembled HMQC micelles as a delivery carrier for poorly water-soluble drugs. The study indicated that the prednisone acetate could be incorporated effectively in the self-assembled HMQC micelles and be controlled released.