Fabrication of tough poly(ethylene glycol)/collagen double network hydrogels for tissue engineering.

In this study, a series of poly(ethylene glycol)/collagen (PEG/Col) double network (DN) hydrogel is fabricated from PEG and Col. Results of the compressive strength test indicate that the strength and toughness of these DN hydrogels are significantly enhanced. The fracture strength of PEG/Col DN hydrogels increases by 9- to 12-fold compared with that of PEG single network (SN) hydrogel, and by 36- to 48-fold compared with that of Col SN hydrogel. Taking advantage of both PEG and Col building blocks, the PEG/Col DN hydrogels possess a strengthened skeleton. Moreover, the water-storage capability and favorable biocompatibility of Col are effectively maintained. Given that the DN hydrogels can provide the appropriate environment for the adhesion, growth, and proliferation of MC3T3-E1 cells, PEG/Col DN hydrogels have potential as a load-bearing tissue repair material. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 192-200, 2018.

[Endocytosis pathway and intracellular distribution of heparosan].

In this study, the endocytosis pathway of heparosan and its intracellular distribution were investigated in MCF-7 tumor cells and COS7 normal cells. The endocytosis inhibition and cellular probe location experiments showed that MCF-7 tumor cells took heparosan more efficiently and selectively than COS7 cells. The cellular uptake of heparosan was energy-dependent in both MCF-7 tumor cells and COS7 normal cells. Moreover, the major endocytosis pathway of heparosan into MCF-7 tumor cells was caveolin-mediated endocytosis and macropinocytosis. The internalized heparosan was mainly located in lysosomes of the cells.

In situ supramolecular hydrogel based on hyaluronic acid and dextran derivatives as cell scaffold.

In this study, hyaluronic acid-ß-cyclodextrin conjugate (HA-CD) and dextran-2-naphthylacetic acid conjugate (Dex-NAA) were synthesized as two gelators. The degrees of substitution (DS) of these two gelators were determined to be 15.5 and 7.4%, respectively. Taking advantages of the strong and selective host-guest interaction between ß-CD and 2-NAA, the mixture of two gelators could form supramolecular hydrogel in situ. Moreover, the pore size, gelation time, swelling ratio as well as modulus of the hydrogel could be adjusted by simply varying the contents of HA-CD and Dex-NAA. NIH/3T3 cells that entrapped in hydrogel grew well as compared with that cultured in plates, indicating a favorable cytocompatibility of the hydrogel. Collectively, the results demonstrated that the HA-Dex hydrogel could potentially be applied in tissue engineering as cell scaffold. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2263-2270, 2016.

One-pot construction of boronate ester based pH-responsive micelle for combined cancer therapy.

In this study, one-pot strategy for the construction of micelles loaded with two types of anticancer drugs (i.e., doxorubicin and methotrexate) together is reported. On the basis of the reaction between boronic acid and 1,2-diol to form boronate ester, the formation of amphiphiles, their self-assembly into micelles and drug encapsulation occurs simultaneously under simple dialysis at the appropriate pH condition. In the one-pot strategy, the micelle yield is high (78.2%) and the drug encapsulation efficiency of the two drugs is improved compared with that of the traditional method. The micelles can selectively increase the drug release ratio at acidic pH, showing the pH-responsive behavior inherited from the property of boronate ester. By combining doxorubicin and methotrexate, the half-maximum inhibition concentrations of the two drugs are obviously reduced, showing synergistic efficacy against cancer cells. This strategy is promising and may be expanded to various applications.

Hyaluronic acid and polyethylenimine self-assembled polyion complexes as pH-sensitive drug carrier for cancer therapy.

In this study, a series of polyion complexes (PICs) were prepared via electrostatic interaction between hyaluronic acid-histidine conjugate (HH) and polyethylenimine-histidine conjugate (PH). These PICs with the average size ranging from 410.5 nm to 98.5 nm at different weight ratios of HH/PH were able to encapsulate doxorubicin (DOX) as the model antitumor drug. The PICs at the weight ratio of 4:1 had negative surface charge and were of good dispersity and stability in the solution containing serum. In vitro drug release assay demonstrated that the DOX release rate were higher at acidic pH showing a controllable property. These HA coated PICs could targetedly deliver DOX to B16F10 tumor cells, showing improved antitumor activity.

Heparosan based negatively charged nanocarrier for rapid intracellular drug delivery.

In this study, a heparosan-DOX conjugate (HDC) was designed and prepared by covalently linking heparosan with anticancer drug doxorubicin (DOX) via "Schiff" base. Due to the amphiphilic nature, the HDC could self-assemble into nanoparticles in aqueous solution of pH 7.4. In spite of the surface charge of HDC nanoparticles was negative, HDC could achieve intracellular delivery of DOX efficiently. Cellular uptake study revealed the endocytosis pathway of heparosan based nanocarrier includes clathrin-mediated endocytosis and macropinocytosis, and the process of endocytosis is energy dependent. This meant the HDC would reach endosomes and behave pH-sensitive DOX release profile due to the inherent property of "Schiff" base. The cytotoxicity assay and flow cytometry analysis demonstrated the cellular uptake of HDC was faster than that of free DOX, showing improved efficacy within short co-incubation period. Furthermore, the HDC nanoparticles were stable in culture medium containing 10% FBS, indicating promising application for drug delivery.

Construction of serum resistant micelles based on heparosan for targeted cancer therapy.

A novel micelle based on heparosan and deoxycholic acid (DOCA) conjugate (HD) as drug carrier was reported here. As the surface was negatively charged, this micelle could resist serum adsorption, showing favorable stability. Moreover, fluorescence observation confirmed that it was able to deliver model hydrophobic drug doxorubicin (DOX) into HeLa cells efficiently. The DOX-loaded micelles showed sustained release behavior at pH 7.4, and accelerated release behavior at pH 5.0 or in the presence of ß-glucuronidase, which over-expressed in tumor cells. In vitro cytotoxicity assay demonstrated that the half-maximal inhibitory concentration (IC50) of DOX-loaded micelles against HeLa cells was much lower than that of COS7 cells, showing significant therapeutic distinction between tumor cells and normal cells. Combining with the good biocompatibility and biodegradability of heparosan, this micelle may be promising in clinical application for targeted drug delivery.

Fabrication of doxorubicin and heparin co-loaded microcapsules for synergistic cancer therapy.

In this study, a layer-by-layer (LbL) assembly (HEP/CHI)5 microcapsule with doxorubicin hydrochloride (DOX) encapsulating inside was fabricated via alternatively depositing heparin (HEP) and chitosan (CHI) onto DOX-loaded CaCO3 templates. The microcapsules were of stable architecture and had good dispersity in aqueous medium. Fluorescence observation showed that DOX distributed both in the wall and in the cavity of microcapsules, while HEP presented in the capsule wall. The release rate of DOX increased at acidic pH as compared with that at basic pH, suggesting a pH-responsive drug release behavior. The microcapsules with positively charged CHI lying on the outer layer could protect HEP from heparanase degradation and achieve intracellular co-delivery of both DOX and HEP. Thus, the DOX-loaded microcapsules could have improved inhibition activity against A549 cells by combining pharmacological actions of DOX and HEP.

Multi-functional envelope-type nanoparticles assembled from amphiphilic peptidic prodrug with improved anti-tumor activity.

A novel multifunctional amphiphilic peptidic prodrug was reported here by conjugating the antitumor drug of doxorubicin (DOX) to the hydrophobic tail of a designed peptide-amphiphile (PA), in which the hydrophilic peptide headgroup comprises a glycine-arginine-glycine-aspartic acid-serine (GRGDS) sequence and octaarginine (R8) sequence. Because of the amphiphilic nature, this peptidic prodrug can spontaneously self-assemble into spherical multifunctional envelop-type nanoparticles (MENPs) with the functional peptide sequences gathered on surface. By means of the multifunctions of RGD-mediated tumor targeting, R8-mediated membrane penetration and intracellular protease-mediated hydrolyzing peptide bonds, the MENPs could targeted deliver doxorubicin (DOX) to tumor cells, showing improved antitumor activity both in vitro and in vivo with much reduced side effects.

A new anti-cancer strategy of damaging mitochondria by pro-apoptotic peptide functionalized gold nanoparticles.

Gold nanoparticles functionalized with pro-apoptotic peptide (PAP-AuNPs) were fabricated, which were able to lead to programmed cell-death by damaging mitochondria.

Self-assembled BolA-like amphiphilic peptides as viral-mimetic gene vectors for cancer cell targeted gene delivery.

In this study, two types of BolA-like amphiphilic peptides with dual ligands comprising a tumor-targeting moiety of RGD sequence and a cell-penetrating moiety of R8 sequence are designed and synthesized as gene vectors. The BolA-structural peptide carriers can self-assemble into spherical nanoparticles with a hydrophilic core and shell, which are similar to the viral capsid and can bind plasmid DNA in an aqueous medium to form viral-mimetic complexes. It is found that the BolA-like dual ligands system exhibits significantly enhanced gene expression in both HeLa and 293T cell lines, as compared with poly(ethylenimine) PEI. These BolA-like amphiphilic peptides are promising in clinical trials of gene therapy.

Novel gene transfer vectors based on artificial recombinant multi-functional oligopeptides.

Viral vectors, except for their safety concern, have shown high efficiency in both delivery and expression of gene. Here, a series of new gene carriers, comprised of short peptide subunits with special functions to imitate viral vectors, were designed and three vectors, (C(18))(2)KH(4)R(8)GDS, AcKH(4)R(8)GDS and (C(18))(2)KH(4)R(8), designated as ARM1, ARM2, ARM3, respectively, were synthesized and evaluated. The transfection efficiency in vitro was studied in terms of 293T, HepG2 and HeLa cell lines. It was found that the transfection efficiency was enhanced significantly for the vectors (ARM1 and ARM3) with double hydrophobic aliphatic tails. Interestingly, the conjugation of RGDS sequence in vectors displayed no obvious difference in cell adhesion for all of the three cell lines. Moreover, confocal laser scanning microscope results indicated that the peptide/pDNA complexes can enter the cell and nuclei successfully. On the other hand, all the vectors displayed low cytotoxicity. The artificial recombinant multi-block oligopeptides (ARMs) demonstrated here might give a promising potential of the peptide-based vectors in gene therapy.

Facile construction of nanofibers as a functional template for surface boron coordination reaction.

A facile strategy to perform the boron coordination reaction on a template of nanofibers is developed. Peptides with phenylboronic acid tails (peptidyl boronic acids) are designed and prepared as building blocks that can self-assemble into nanofibers. After the addition of vicinal diol structural motifs to the self-assembling system, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry indicates that the boron coordination reaction occurs on the template of nanofibers, which results in the increase of the width and roughness of the nanofibers as demonstrated by transmission electron microscopy and atomic force microscopy measurements. Because the surface-bound vicinal diol structural motifs have an ability to form hydrogen bonds with the peptide segments on the nanofibers, which restrain and disturb the hydrogen-bonding interaction among the nanofibers, the network structure formed based on the entanglement of nanofibers via hydrogen-bonding interaction is destroyed, which leads to a gel-sol transition. The novel concept of post-self-assembly modification demonstrated here could lead to a new technique for using self-assembled nanostructures in the emerging fields of nanoscience and nanotechnology.

Surface self-assembly of N-fluorenyl-9-methoxycarbonyl diphenylalanine on silica wafer.

N-Fluorenyl-9-methoxycarbonyl diphenylalanine (Fmoc-FF-OH) was chemically immobilized to the surface of silica wafer as the "seed". When immersing this peptide attached silica wafer into the dipeptide aqueous solution, the occurrence of a pH triggered surface self-assembly resulted in the formation of peptide nanorods on the surface of silica wafer. This surface self-assembly exhibited a dependence on the concentration of the dipeptide aqueous solution. It was proposed that the self-assembly of this dipeptide on the surface of silica wafer was similar to that in aqueous solution. In comparison with the conventional physical adsorption on the substrates, the chemically attached self-assembled nanorods exhibited much improved adsorption capacity on the substrate surface.

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 ß-sheet conformation. The strategy demonstrated here presents great potential for preparation of well-defined nanostructures via rationally designing the molecular structures of cyclopeptides.

Construction of surfactant-like tetra-tail amphiphilic peptide with RGD ligand for encapsulation of porphyrin for photodynamic therapy.

A surfactant-like tetra-tail amphiphilic peptide, [(C(18))(2)K](2)KR(8)GRGDS was designed and synthesized for targeted drug delivery. The resulting peptide-amphiphile, consisting of four hydrophobic aliphatic tails and a hydrophilic peptide head group, was able to self-assemble into nanosized micelles in aqueous medium at low concentration. Ibuprofen and doxorubicin (DOX) was loaded into peptide micelles as model hydrophobic drugs respectively, and the sustained release behavior was observed. Due to the incorporation of targeted arginine-glycine-aspartic acid (RGD) sequences and cell penetrating peptide (CPP) residue octaarginine (R(8)), the micelles could be recognized specifically by cancer cells, as well as transport through the cell membrane efficiently. The observation of laser-scanning confocal microscopy confirmed effective cellular uptaking of porphyrin-loaded peptide micelles. Furthermore, the porphyrin-loaded micelles exhibited low dark toxicity and high phototoxicity against cancer cells, indicating the powerful potential for effective photodynamic therapy. Combined with the low cytotoxicity of the peptide against both HeLa and 293T cell lines, the surfactant-like peptide developed in this study may be promising in clinical application for targeted drug delivery.

Construction of cell penetrating peptide vectors with N-terminal stearylated nuclear localization signal for targeted delivery of DNA into the cell nuclei.

Cellular uptake and nuclear localization are two barriers to gene delivery. Here, we designed new gene delivery carriers with an N-terminal stearylated (STR) nuclear localization signal (NLS), PKKKRKV, present in the Simian Virus 40 large T antigen with the aim to overcome limitations, such as cell membrane and nuclear pores, offering attractive possibilities to enhance gene delivery. Four vectors with different structures of N-stearylated nuclear localization signal-octaarginine peptide (STR-PKKKRKV-R(8) or STR-NLS-R(8), STR-VKRKKKP-R(8) or STR-reverse NLS-R(8), PKKKRKV-R(8) or NLS-R(8), and VKRKKKP-R(8) or reverse NLS-R(8)) were compared. The gene expression mediated by these vectors in dividing and non-dividing cells (both in 293T and HeLa cell lines) was investigated. The most efficient N/P ratio was 4 for STR-PKKKRKV-R(8,) STR-VKRKKKP-R(8,) and 0.25 for PKKKRKV-R(8), VKRKKKP-R(8.) The maximum transfection activity of these vehicles (VKRKKKP-R(8)) was up to 80% as effective as jetPEI™ and the vehicles did not exhibit cytotoxicity. Interestingly, N-stearylated peptides presented lower transfection activity compared to peptides without N-stearylation at lower N/P ratios (0.25 to 1). Confocal study showed that the vectors could effectively promote the nuclear translocation.

Core-shell nanosized assemblies mediated by the alpha-beta cyclodextrin dimer with a tumor-triggered targeting property.

In this paper, the alpha-beta cyclodextrin dimer is designed via "click" chemistry to connect the hydrophilic and hydrophobic segments to form self-assembled noncovalently connected micelles (NCCMs) through host-guest interactions. A peptide containing the Arg-Gly-Asp (RGD) sequence was introduced to NCCMs as a target ligand to improve the cell uptake efficacy, while PEGylated technology was employed via benzoic-imine bonds to protect the ligands in normal tissues and body fluid. In addition, two fluorescent dyes were conjugated to different segments to track the formation of the micelles as well as the assemblies. It was found that the targeting property of NCCMs was switched off before reaching the tumor sites and switched on after removing the poly(ethylene glycol) (PEG) segment in the tumor sites, which was called "tumor-triggered targeting". With deshielding of the PEG segment, the drugs loaded in NCCMs could be released rapidly due to the thermoinduced phase transition. The new concept of "tumor-triggered targeting" proposed here has great potential for cancer treatment.

Amphiphilic cationic lipopeptides with RGD sequences as gene vectors.

Two kinds of arginine-rich amphiphilic lipopeptides with hydrophobic aliphatic tails (C(12)GR(8)GDS, LP1 and C(18)GR(8)GDS, LP2) were designed and synthesized as functional gene vectors. With hydrophobic tail modification, these amphiphilic lipopeptides could bind DNA more efficiently and form stable spherical complexes in comparison with the control peptide (AcGR(8)GDS, P1). Moreover, the size and zeta potential results demonstrated the charge density and stability of the vector/DNA complexes could be improved with the increasing length of the aliphatic tails. In vitro transfection experiments showed that LP1 and LP2 could induce much higher gene expression level (luciferase expression) as compared with P1. Due to the incorporation of arginine-glycine-aspartic acid (RGD) sequences which could be specifically recognized by integrins alpha(upsilon)beta(3) and alpha(upsilon)beta(5) over-expressed on cancer cells, these lipopeptides could be specifically recognized by cancer cells, i.e. LP1 and LP2 exhibited relatively higher transfection efficiency in HeLa cell line than that of P2 and P3 without RGD sequence. While the transfection efficiencies of LP2 and P2 were similar in 293T cells. Lipopeptides exhibited very low cell cytotoxicity in both HeLa and 293T cell lines even at high concentration.