Si-Yong Qin

Theranostic GO‐Based Nanohybrid for Tumor Induced Imaging and Potential Combinational Tumor Therapy

Graphene oxide (GO)-based theranostic nanohybrid is designed for tumor induced imaging and potential combinational tumor therapy. The anti-tumor drug, Doxorubicin (DOX) is chemically conjugated to the poly(ethylenimine)-co-poly(ethylene glycol) (PEI-PEG) grafted GO via a MMP2-cleavable PLGLAG peptide linkage. The therapeutic efficacy of DOX is chemically locked and its intrinsic fluorescence is quenched by GO under normal physiological condition. Once stimulated by the MMP2 enzyme over-expressed in tumor tissues, the resulting peptide cleavage permits the unloading of DOX for tumor therapy and concurrent fluorescence recovery of DOX for in situ tumor cell imaging. Attractively, this PEI-bearing nanohybrid can mediate efficient DNA transfection and shows great potential for combinational drug/gene therapy. This tumor induced imaging and potential combinational therapy will open a window for tumor treatment by offering a unique theranostic approach through merging the diagnostic capability and pathology-responsive therapeutic function.

Self-delivery of a peptide-based prodrug for tumor- targeting therapy

A novel self-delivered prodrug system was fabricated for tumor-targeting therapy. In this nanosystem, the Arg-Gly-Asp-Ser (RGDS) tetrapeptide was used to improve the therapeutic index to integrin-overexpressing tumor cells. The antitumorous drug camptothecin was further appended to the ε-amino group of lysine by 20-O-succinyl linkage and controllably released via hydrolytic cleavage. Prodrug molecules self-assembled into fibrillar nano-architectures and achieved the capability of self-delivery after being injected subcutaneously into mice. Introduction of hydrophobic myristic acid favored the self-assembly and enhanced the cellular internalization of the prodrugs. In vitro and in vivo studies demonstrated that the self-assembled nanofibers could effectively target integrinoverexpressing tumorous cells and inhibit tumor growth via RGD-mediated specific targeting. Therefore, the traditional idea that fibrillar structures hold low therapeutic efficacy due to poor cell uptake can be challenged.

Tyroserleutide-based gene vector for suppressing VEGF expression in cancer therapy.

A small interfering RNA (siRNA) plasmid DNA (pYr-1.1-hU6-EGFP-siVEGF) was constructed and used for suppressing vascular endothelial growth factor (VEGF) expression and inhibiting tumor growth. Then, a (tyrosyl-seryl-leucine)-polyethyleneimine-poly(ethylene glycol) (YSL-PEI-PEG) conjugate was designed and synthesized as a gene carrier for the delivery of pYr-1.1-hU6-EGFP-siVEGF plasmid. The therapeutic peptide YSL was conjugated to PEI to improve the anti-cancer efficiency, and the PEG chain was introduced to reduce the serum protein adsorption and improve the stability of the complex in the systemic circulation. It was found that YSL-PEI-PEG could efficiently condense plasmid DNA when the vector/DNA weight ratio was higher than 2. Compared with PEI 25 kDa, YSL-PEI-PEG exhibited higher transfection efficiency and lower cytotoxicity. More importantly, the results showed that the gene delivery system owned strong ability to inhibit cancer cell proliferation in vitro and tumor growth in vivo. YSL-PEI-PEG has great potential as a gene vector for clinical applications.

Hierarchical self-assembly of a β-amyloid peptide derivative

Neurodegenerative diseases including Alzheimers, Parkinsons, and type II diabetes are recognized to be related to proteins misfolding into amyloid fibrils and other aggregates with a β-sheet conformation. Herein, self-assembled peptide micro/nanoarchitectures were designed and prepared to mimic those aggregates. A short β-amyloid peptide derivative with a diphenylalanine moiety was synthesized, which could self-assemble into nanofibers viaβ-sheet conformation in an aqueous solution with a concentration of 1 mg mL-1 at pH about 8. By adjusting the pH to around 6.5, a peptide solution with a concentration of 15 mg mL-1 could change to a supramolecular hydrogel. The influence of self-assembly conditions including peptide concentration, temperature, pressure, and self-assembly time were investigated in detail. It was found that the self-assembled nanofibers could further aggregate into catenulate microfibers in solution as well as layer-by-layer plaques in the hydrogel under particular conditions.

Morphology Transformation via pH-Triggered Self-Assembly of Peptides

Three flexible peptides (P1: (C(17)H(35)CO-NH-GRGDG)(2)KG; P2: (Fmoc-GRGDG)(2)KG; P3: (CH(3)CO-NH-GRGDG)(2)KG) self-assembled to form a variety of morphologically distinct assemblies at different pHs. P1 formed nanofibers at pH 3, then self-assembled into nanospheres with pH up to 6 and further changed to lamellar structures when the pH value was further increased to 10. P2 aggregated into an entwined network structure at pH 3, and then self-assembled into well-defined nanospheres, lamellar structures, and vesicles via adjusting the pH value. However, P3 did not self-assemble into well-ordered nanostructures, presumably due to the absence of a large hydrophobic group. The varying self-assembly behaviors of the peptides at different pHs are attributed to molecular conformational changes. These self-assembled supramolecular materials might contribute to the development of new peptide-based biomaterials.

Fabrication of dual responsive co-delivery system based on three-armed peptides for tumor therapy

Introducing drugs into gene delivery systems to fabricate co-delivery systems for synergy therapy has become a promising strategy for tumor therapy. In this study, a dual responsive co-delivery system RHD/p53 was fabricated to enhance the antitumor efficacy with a low dose of doxorubicin (DOX). The reducible branched cationic polypeptide (RBCP), which was cross-linked via the thiol groups of two three-armed cationic peptides (CRR)2KRRC and (CHH)2KHHC, was designated as RH. Then, DOX was immobilized on RH via pH-sensitive hydrazone bonds to obtain RHD. The positively charged RHD could compress p53 plasmid to form RHD/p53 complexes. After RHD/p53 complexes accumulated in tumor sites, the ability of cell penetrating by cationic peptide (CRR)2KRRC would facilitate the cellular internalization of complexes. Then, the complexes would be trapped in endosome, and the cleavage of hydrazone bonds in the intracellular acidic endosome could lead to pH-induced release of DOX. Additionally, the ability of protonation by (CHH)2KHHC could promote the escape of complexes from endosome to cytoplasm. Due to the cleavage of disulfide bonds triggered by the high-content GSH in cytoplasm, the complexes would be degraded and released p53 for co-therapy to improve antitumor efficacy. Both in vitro and in vivo studies indicated that dual responsive co-delivery system RHD/p53 could enhance antitumor efficacy, which provides a useful strategy for co-delivery of different therapeutic agents in tumor treatment.

Evaluating the Effects of Charged Oligopeptide Motifs Coupled with RGD on Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells, due to their multilineage differentiation potential, have emerged as a promising cell candidate for cell-based therapy. In recent years, biomaterials were artificially synthesized to control the differentiation of mesenchymal stem cells. In this study, a series of charged or neutral oligopeptide motifs coupled with RGD were synthesized and used for surface modification using quartz substrates as model. Cell behaviors on the modified surfaces with different charged oligopeptide motifs were studied. It was found that these different charged oligopeptide motifs coupled with RGD were biocompatible for cell proliferation and adhesion. Moreover, it was demonstrated that the positively charged oligopeptide motif could inhibit osteogenic differentiation, while the negatively charged and neutral oligopeptide motifs could enhance osteogenic differentiation in the presence of RGD. This work may bring us enlightenment that different charged oligopeptide motifs coupled with RGD may be used for biomaterial surface modification for different stem cell-based therapies.

Peptide-based vector of VEGF plasmid for efficient gene delivery in vitro and vessel formation in vivo.

Critical limb ischemia is regarded as a potentially lethal disease, and the treatment effects of existing therapies are limited. Here, in order to develop a potential approach to improve the therapy effects, we designed a peptide of TAT-PKKKRKV as the vector for VEGF165 plasmid to facilitate in vivo angiogenesis. In in vitro studies, TAT-PKKKRKV with low cytotoxicity exhibited efficient transfection ability either with or without serum. Additionally, application of TAT-PKKKRKV/VEGF165 complexes in hindlimb ischemia rats obviously promoted the expression of VEGF protein, which further enhanced effective angiogenesis. The results indicated that TAT-PKKKRKV is an efficient gene vector with low toxicity both in vitro and in vivo, which has great potential for clinical gene therapy.

Controllable micro/nanostructuresvia hierarchical self-assembly of cyclopeptides

Peptide self-assembling materials have recently emerged as one of the most promising biomaterials. In this study, we synthesized three amphipathic cyclopeptides (CPs1–3) with systematically modified side chains to control the morphologies of self-assembly. Owing to the varying modifications of the side chains, various micro/nanostructures were achieved because of different driving forces. The obtained morphologies were characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). Apart from hydrogen bond interactions for CPs, CP1 self-assembles into spindle-like aggregates with an average diameter of 70 nm and a length of 300 nm owing to the salt-bridge interactions in a neutral medium. CP2 can form micro/nanotubes with the diameters ranging from 750 nm to 2 μm via the hydrophilic and hydrophobic interactions between the cyclopeptide ring and the alkyl chain. While CP3 forms solid nanospheres with an average diameter of 516 nm through aromatic-aromatic π–π interactions. This approach can lead to the fabrication of new functional supramolecular assemblies and materials and broaden the insights for the mechanism of the self-assembly.

Supramolecular architectures self-assembled from asymmetrical hetero cyclopeptides.

In this study, two asymmetrical cyclopeptides (CP1 and CP2) were designed and synthesized. The self-assembly behaviors of the asymmetrical cyclopeptides at varying pHs were investigated in terms of transmission electron microscopy (TEM), circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. It was found that the self-assembly of CP1 resulted in the formation of nanofibers with α-helix conformation, while CP2 self-assembled into well-ordered nanorods with anti-parallel β-sheet conformation. The strategy demonstrated here presents great potential for preparation of well-defined nanostructures via rationally designing the molecular structures of cyclopeptides.