Hongping Deng

Aptamer-Functionalized and Backbone Redox-Responsive Hyperbranched Polymer for Targeted Drug Delivery in Cancer Therapy

A novel type of backbone redox-responsive hyperbranched poly(2-((2-(acryloyloxy)ethyl)disulfanyl)ethyl 4-cyano-4-(((propylthio)carbonothioyl)-thio)-pentanoate-co-poly(ethylene glycol) methacrylate) (HPAEG) has been designed and prepared successfully via the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization and self-condensing vinyl polymerization (SCVP). Owing to the existence of surface vinyl groups, HPAEG could be efficiently functionalized by DNA aptamer AS1411 via Michael addition reaction to obtain an active tumor targeting drug delivery carrier (HPAEG-AS1411). The amphiphilic HPAEG-AS1411 could form nanoparticles by macromolecular self-assembly strategy. Cell Counting Kit-8 (CCK-8) assay illustrated that HPAEG-AS1411 nanoparticles had low cytotoxicity to normal cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) results demonstrated that HPAEG-AS1411 nanoparticles could be internalized into tumor cells via aptamer-mediated endocytosis. Compared with pure HPAEG nanoparticles, HPAEG-AS1411 nanoparticles displayed enhanced tumor cell uptake. When the HPAEG-AS1411 nanoparticles loaded with anticancer drug doxorubicin (DOX) were internalized into tumor cells, the disulfide bonds in the backbone of HPAEG-AS1411 were cleaved by glutathione (GSH) in the cytoplasm, so that DOX was released rapidly. Therefore, DOX-loaded HPAEG-AS1411 nanoparticles exhibited a high tumor cellular proliferation inhibition rate and low cytotoxicity to normal cells. This aptamer-functionalized and backbone redox-responsive hyperbranched polymer provides a promising platform for targeted drug delivery in cancer therapy.

GFP-inspired fluorescent polymer

Inspired by the green fluorescent protein (GFP), a novel amphiphilic fluorescent polymer was designed and synthesized. The amphiphilic polymer showed enhanced fluorescent properties after self-assembly into micellar aggregates. Moreover, the fluorescence enhancement behavior of the GFP-inspired polymer through self-assembly was successfully applied in cell imaging.

Temperature-induced fluorescence enhancement of GFP chromophore containing copolymers for detection of Bacillus thermophilus

Green fluorescent protein (GFP) chromophore based copolymers with temperature-induced emission enhancement properties were successfully prepared and applied for biodetection. First, diblock copolymers (PEG-b-PNIPAM-c) with different poly(N-isopropylacrylamide) (PNIPAM) chain lengths were synthesized by atom transfer radical polymerization (ATRP) employing a poly(ethylene glycol) (PEG) macroinitiator and then modified with a GFP chromophore at one chain end through a click reaction. Owing to the different PNIPAM chain lengths, the block copolymers exhibited thermoresponsive phase transitions with adjustable lower critical solution temperature (LCST). Above the LCST, the fluorescence intensity of PEG-b-PNIPAM-c was enhanced dramatically, which could be attributed to the chromophores conformational restriction by the collapse of PNIPAM blocks. Moreover, the emission intensity of PEG-b-PNIPAM-c increased with the PNIPAM chain length. Correspondingly, the temperature-dependent fluorescence enhancement properties of PEG-b-PNIPAM-c were successfully applied in the highly sensitive detection of Bacillus thermophilus with a 102 cfu per mL detection limit.

pH-responsive flower-like micelles constructed via oxime linkage for anticancer drug delivery

A new type of pH-responsive flower-like micelle based on backbone-cleavable triblock copolymer polycaprolactone-oxime-poly(ethylene glycol)-oxime-polycaprolactone (PCL-OPEG-PCL) was developed for anticancer drug delivery. Firstly, PCL-OPEG-PCL was synthesized by ring-opening polymerization. The structure of PCL-OPEG-PCL was confirmed by 1H NMR and Fourier transform infrared spectroscopy (FTIR). Benefiting from the amphiphilic character and unique molecular architecture with the hydrophilic PEG and hydrophobic PCL segments, PCL-OPEG-PCL could self-assemble into flower-like micelles in aqueous solution, which has been demonstrated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The cytotoxicity of the flower-like micelles was evaluated by MTT assay against NIH/3T3 normal cells. Doxorubicin (DOX), a model anticancer drug, was encapsulated into these flower-like micelles with high efficiency. The in vitro study showed that DOX-loaded flower-like micelles possessed high stability at physiological pH of 7.4, whereas the DOX release from the flower-like micelles was significantly accelerated at mildly acidic pH of 5.0, demonstrating the pH-responsive feature of the drug carrier with oxime linkages. DOX-loaded flower-like micelles were investigated for proliferation inhibition of Hela cells in vitro, and the DOX dose required for 50% cellular growth inhibition was found to be 1.81 μg mL−1. All of these results demonstrate that flower-like micelles self-assembled from PCL-OPEG-PCL triblock copolymers can be used as effective and promising drug nanocarriers.

Multi-color cell imaging under identical excitation conditions with salicylideneaniline analogue-based fluorescent nanoparticles

Six salicylideneaniline (SA) derivatives are synthesized through a condensation reaction. Benefiting from their coplanar molecular conformation and intramolecular hydrogen bonds, three of the compounds are found to exhibit aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) behavior after self-assembling into nanoparticles that have a diameter of about 50 nm. Based on the excited-state intramolecular proton transfer (ESIPT) properties, these fluorescent nanoparticles (FNPs) display green, yellow or orange colors due to the formation of H- or J-aggregates. Interestingly, FNPs derived from BMSpP show green to green-yellow fluorescence because of the partial transformation of H-aggregates to J-aggregates. Under neutral conditions (pH = 7.4), these FNPs are stable, with the fluorescence intensity decreasing by less than 20% after 120 min, compared to a rapid reduction at pH 5.5. Importantly, a two-photon fluorescence property of FNPs originating from salicylideneaniline or its derivatives is reported for the first time. The two-photon absorption cross-sections of the green, yellow and orange FNPs are found to be 7, 38 and 27 GM, respectively. After conjugation with phospholipids, these FNPs show good water solubility and low cytotoxicity, which make them potential candidates for cell imaging applications. Finally, multi-color cell imaging under identical excitation conditions with single-emissive and multi-emissive FNPs has been achieved. These results are significant for the control of the one- or two-photon fluorescent properties of such derivatives, and provide a promising platform for multi-color cell imaging applications.

Effect of branching architecture on the optical properties of polyazomethines

The architecture of conjugated polymers has an important influence on their optical and electrical properties. In this study, the effect of branching architecture on the optical properties of polyazomethines (PAs) was investigated. Linear and branched PAs with degree of branching (DB) ranging from 0 to 0.52 were successfully synthesized through homogeneous condensation by changing the feeding ratios of diamine, tetramine and dialdehyde. All PAs showed good thermal stability, and their decomposition temperature was over 380 °C. Both UV-Vis absorption and fluorescence emission demonstrated that the optical properties of PAs were closely related to the DB. With the increase of DB, an obvious redshift was found in UV-Vis absorption spectra, and the fluorescence maximum emission intensity (FMEI) and relative fluorescence quantum efficiency (RFQE) initially increased to a maximum and then gradually diminished to almost zero. These phenomena could be attributed to the antagonistic effect between the auxochromic effect of amino groups and the intra- and inter-molecular interactions. To confirm this mechanism, the intra- and inter-molecular interactions were purposely broken by adding trifluoroacetic acid (TFA) and SnCl2, which resulted in an increase in FMEI. Therefore, the optical properties of conjugated polymers can be readily adjusted by changing the DB of polymers.

Self-Restricted Green Fluorescent Protein Chromophore Analogues: Dramatic Emission Enhancement and Remarkable Solvatofluorochromism.

The confinement effect of the β-barrel defines the emission profiles of the chromophores of the green fluorescent protein (GFP) family. Here, we describe the design strategy and mimicking of confinement effects via the chromophore itself, termed the self-restricted effect. By systematically tailoring the GFP core, a family of 2,5-dialkoxy-substituted GFP chromophore analogues is found to be highly emissive and show remarkable solvatofluorochromism in fluid solvents. Fluorescence quantum yield (QY) and lifetime measurements, in combination with theoretical calculations, illustrate the mechanism relying on inhibition of torsional rotation around the exocyclic CC bond. Meanwhile, theoretical calculations further reveal that the electrostatic interaction between the solvent and the imidazolinone oxygen can contribute to suppress the radiationless decay channel around the exocyclic C═C double bond. Our findings put forward a universal approach toward unlocked highly emissive GFPc analogues, potentially promoting the understanding of the photophysics and biochemical application of GFP chromophore analogues.

Real-time self-tracking of an anticancer small molecule nanodrug based on colorful fluorescence variations

A new self-tracking nanoscale drug delivery system has been developed to monitor drug delivery and release in tumor cells. The small molecule nanodrug was constructed via the conjugation and self-assembly of two widely used anticancer drugs, hydrophilic irinotecan (Ir) which displays blue fluorescence and hydrophobic doxorubicin (DOX) which displays red fluorescence, which produced colorful fluorescence variations during drug delivery and release in cells. Owing to the fluorescence resonance energy transfer (FRET), the Ir–DOX conjugate emitted strong red fluorescence when excited at a short wavelength. Benefiting from its amphiphilicity, the Ir–DOX conjugate self-assembled into micelles in aqueous medium and the fluorescence was quenched due to aggregation-caused quenching (ACQ). No obvious red or blue fluorescence was observed during a 12 h cell incubation with Ir–DOX, indicating that Ir–DOX entered cells in the form of micelles rather than free conjugate or free drugs. With increasing incubation time, the breaking of the Ir–DOX linkage resulted in the release of both free drugs, leading to the recovery of dual-color fluorescence. In vitro cytotoxicity studies showed that the Ir–DOX micelles could overcome the multidrug resistance (MDR) of tumor cells, resulting in a prominent growth inhibition against cancer cell proliferation. The Ir–DOX small molecule nanodrug provides a new design for real-time self-tracking of carrier-free and probe-free drug delivery systems in cancer treatment.

A Molecular Recognition Approach To Synthesize Nucleoside Analogue Based Multifunctional Nanoparticles for Targeted Cancer Therapy

Tumor-targeted drug delivery with simultaneous cancer imaging is highly desirable for personalized medicine. Herein, we report a supramolecular approach to design a promising class of multifunctional nanoparticles based on molecular recognition of nucleobases, which combine excellent tumor-targeting capability via aptamer, controlled drug release, and efficient fluorescent imaging for cancer-specific therapy. First, an amphiphilic prodrug dioleoyl clofarabine was self-assembled into micellar nanoparticles with hydrophilic nucleoside analogue clofarabine on their surface. Thereafter, two types of single-stranded DNAs that contain the aptamer motif and fluorescent probe Cy5.5, respectively, were introduced onto the surface of the nanoparticles via molecular recognition between the clofarabine and the thymine on DNA. These drug-containing multifunctional nanoparticles exhibit good capabilities of targeted clofarabine delivery to the tumor site and intracellular controlled drug release, leading to a robust and effective antitumor effect in vivo.

Construction of a Supramolecular Drug–Drug Delivery System for Non-Small-Cell Lung Cancer Therapy

Nanoscale drug delivery systems (DDSs) are generally considered to be an effective alternative to small molecular chemotherapeutics due to improved accumulation in the tumor site and enhanced retention in blood. Nevertheless, most DDSs have low loading efficiency or even pose a high threat to normal organs from severe side effects. Ideally, a supramolecular drug-drug delivery system (SDDDS) composed of pure drugs via supramolecular interaction provides a hopeful approach for cancer treatment. Herein we propose a facile method to construct SDDDS via coassembly of gefitinib (GEF) and tripeptide tyroservatide (YSV), two kinds of chemotherapeutic pharmaceuticals for non-small-cell lung cancer (NSCLC) via multiple intermolecular interactions, including hydrogen bonding and π-π stacking. As shown through transmission electron microscopy (TEM) and dynamic light scattering (DLS), GEF and YSV self-assemble into nanoparticles with regular morphology and uniform size, which facilitates the delivery of both drugs. In vitro studies demonstrate that the SDDDS is much more efficient in entering cancer cells and inhibiting the proliferation of cancer cells compared with single GEF, YSV, or GEF/YSV drug mixture. In vivo experiments show that the SDDDS can selectively accumulate in tumor tissue, resulting in much better drug efficacy without evident side effects. Considering the advantages of the SDDDS, we believe this strategy provides a promising route for enhanced anticancer therapy in nanomedicine.