RESUMO
We reported the fabrication of several monodispersed poly(2-vinyl pyridine)-poly(N-isopropylacrylamide) (P2VP-PNIPAM) microgels including the P2VP core (non-cross-linked) and PNIPAM (cross-linked) shell by mature emulsion polymerization. The fast escape behavior (diffusion process) of linear P2VP chains through a porous PNIPAM layer was investigated by a pH jump stopped-flow apparatus. The time-dependent dynamic traces (corresponding to the scattered light intensity) decreased at the initial timescale of several seconds and then reached an apparent equilibrium, confirming the efficient escape of P2VP chains from microgels. Compared with the previously reported literature, such an accelerated escape process resulted from the sharply increased internal charge repulsive force caused by the protonation of P2VP moieties under acidic conditions. The obtained characteristic relaxation times by single exponential fitting of these kinetic traces were dependent on the final pH values, equilibrium temperatures, shell thickness (path length), and cross-linking density (mesh size). We believe that this work can provide an efficient way to investigate hindered diffusion, especially the initial rapid diffusion stage. Not only that, the proposed model can also provide theoretical guidance to some practical applications, such as membrane separation and the exocytosis phenomenon of intracellular proteins or macromolecular substances.
RESUMO
In cancer treatment, prolonging the retention time of therapeutic agents in tumor tissues is a key point in enhancing the therapeutic efficacy. However, drug delivery by intravenous injection is always subjected to a "CAPIR" cascade, including circulation, accumulation, penetration, internalization, and release. Intratumoral administration has gradually emerged as an ideal alternative approach for nanomedicine because of its independence of blood constituents and minimal systemic toxicities. In this contribution, based on the dynamically reversible interaction between boronic acid (BA) and dopamine (DA), a thermo- and pH-responsive polymeric complex is rationally obtained by facile mixing of phenylboronic acid (PBA)- and tetraphenylethene (TPE)-modified poly(N-isopropylacrylamide)-b-poly(phenyl isocyanide)s block copolymers, PNIPAM-b-P(PBAPI-co-TPEPI), and tetra(ethylene glycol) methyl ether acrylate (OEGA)- and DA-containing hydrophilic P(DA-co-OEGA) copolymers. The resultant complex exhibited temperature- and pH-dependent size change as well as sustained nile red (NR) release profiles in a mimic tumor environment. Moreover, thanks to the opposite optical behavior of TPE and NR molecules, the complex could be served as a fluorescence ratiometric cell imaging agent, avoiding the interference of background fluorescence and improving correlated resolution. After encapsulation of camptothecin (anticancer drug), the efficient killing on HeLa cells was achieved in vitro, and the structural integrity of the complex endowed its extended retention time in tumor tissues. Considering these advantages, the reversible covalent interaction between PBA and diols can be used as an efficient driving force to form dynamic drug-delivery vectors, which are promising to be an effective nanoplatform for injectable medical treatments.