Shaobing Zhou

Osteoblast function on electrically conductive electrospun PLA/MWCNTs nanofibers

The electrospinning process was utilized successfully to fabricate the random oriented and aligned electrically conductive nanofibers of biodegradable poly-DL-lactide (PLA) in which multiwalled carbon nanotubes (MWCNTs) were embedded. The topographical features of the composite nanofibers were characterized by SEM. The dispersion and alignment of MWCNTs in nanofiber matrix were observed by TEM. The in vitro degradation was characterized in terms of the morphological change, the mass loss and the reduction of polymer molecular weight as well as the decrease of pH value of degradation media. In particular, these conductive nanofiber meshes offered a unique system to study the synergistic effect of topographic cues and electrical stimulation on osteoblasts outgrowth as a way of exploring their potential application in bone tissue engineering. The results of obsteoblasts assay unstimulated showed that the aligned nanofibers as topographic cues could enhance the extension and direct the outgrowth of obsteoblasts better than random fibers. In the presence of direct current (DC) of 100 μA, the obsteoblasts on all samples grew along the electrical current direction. The cellular elongation and proliferation were mainly dependent on the electrical stimulation whereas the topographical features played a minor role in them. Therefore, electrical stimulation with an appropriate DC value imparted on conductive substrate had great potential in application of bone tissue engineering.

pH-triggered intracellular release from actively targeting polymer micelles

Chemotherapy is widely applied to treat cancer patients but its application is limited due to the systemic toxicity and low efficacy. Nanocarrier system, which is capable of delivering their toxic cargos specifically into cancer cells and then greatly overcomes these disadvantages, has drawn a broad attention. Here we developed a drug-conjugated micelle for a better drug delivery in which folic acid was attached to the DOX-conjugated poly(ethylene glycol)-poly(ε-caprolactone) to target tumor; DOX was further connected with a hydrazone linker (FA-hyd) for a pH-triggered drug release. Comparing to other DOX-conjugated micelles either linked with carbamate (FA-cbm) or lacking FA(m-hyd), the developed FA-hyd demonstrated excellent biocompatibility; When analyzed with Alamar blue assays, flow cytometry and confocal laser scanning microscopy (CLSM), the pH-sensitive FA-functionalized DOX-conjugated micelles presented much better efficiency of cellular uptake and higher cytotoxicity to tumor cells. In vivo pharmacokinetics and biodistribution studies indicated that FA-hyd micelles significantly prolonged the blood circulation time of drug and enriched drug into the tumors rather than normal tissues. In vivo antitumor activity demonstrated that FA-hyd micelles had the highest safety to body and the best therapeutic efficacy to tumors. Therefore, this drug delivery system is deemed as a potential nanocarrier for cancer therapy.

Hydroxyapatite nucleation and growth mechanism on electrospun fibers functionalized with different chemical groups and their combinations

Controlled nucleation and growth of hydroxyapatite (HA) crystals on electrospun fibers should play important roles in fabrication of composite scaffolds for bone tissue engineering, but no attempt has been made to clarify the effects of chemical group densities and the cooperation of two and more groups on the biomineralization process. The aim of the current study was to investigate into HA nucleation and growth on electrospun poly(dl-lactide) fibers functionalized with carboxyl, hydroxyl and amino groups and their combinations. Electrospun fibers with higher densities of carboxyl groups, combination of hydroxyl and carboxyl groups with the ratio of 3/7, and combination of amino, hydroxyl and carboxyl groups with the ratio of 2/3/5 were favorable for HA nucleation and growth, resulting in higher content and lower crystal size of formed HA. Carboxyl groups were initially combined with calcium ions through electrostatic attraction, and the introduction of hydroxyl groups could modulate the distance between carboxyl groups. The introduction of amino groups may lead to the inner ionic bonding with carboxyl groups, but can accelerate phosphate ions to form HA through a chelate ring with the calcium ion and carbonyl oxygen. The biological evaluation indicated that the mineralized scaffolds acted as an excellent cell support to maintain desirable cell-substrate interactions, to provide favorable conditions for cell proliferation and to stimulate the osteogenic differentiation.

Controlled dual delivery of BMP-2 and dexamethasone by nanoparticle-embedded electrospun nanofibers for the efficient repair of critical-sized rat calvarial defect.

There is an urgent need to develop biomimetic bone tissue engineering scaffolds for the repair of critical-sized calvarial defect. In this study, we developed a new nanoparticle-embedded electrospun nanofiber scaffold for the controlled dual delivery of BMP-2 and dexamethasone (DEX). The scaffold was achieved by (1) the encapsulation of BMP-2 into bovine serum albumin (BSA) nanoparticles to maintain the bioactivity of BMP-2 and (2) the co-electrospinning of the blending solution composed of the BSA nanoparticles, DEX and the poly(ε-caprolactone)-co-poly(ethylene glycol) (PCE) copolymer. The in vitro studies showed that the bioactivity of DEX and BMP-2 was preserved in the dual-drug-loaded nanofiber scaffold, and a sequential release pattern in which most of the DEX was released in the original eight days and the BMP-2 release lasted up to 35 days was achieved. The in vitro osteogenesis study demonstrated that the drug-loaded groups exhibited a strong ability to induce differentiation toward osteoblasts. In vivo osteogenesis studies also revealed that the degrees of repair of rat calvarial defect achieved with the drug-loaded nanofiber scaffolds were significantly better than those obtained with the blank materials; in particular, the dual-drug-loaded nanofiber scaffold manifested the best repair efficacy due to a synergistic effect of BMP-2 and DEX. Therefore, the dual-drug-loaded nanofiber scaffold is deemed a strong potential candidate for the repair of bone defects in bone tissue engineering.

Electro-active Shape Memory Properties of Poly(ε-caprolactone)/Functionalized Multiwalled Carbon Nanotube Nanocomposite

One type of electroactive shape memory nanocomposite was fabricated, including cross-linked poly(ε-caprolactone) (cPCL) and conductive multiwalled carbon nanotubes (MWNTs). The cross-linking reaction of the pristine poly(ε-caprolactone) (PCL) was realized by using benzoyl peroxide (BPO) as an initiator. The raw MWNTs (Raw-M) were prefunctionalized by acid-oxidation process and covalent grafting with poly (ethylene glycol) (PEG), respectively. Three kinds of nanocomposites containing cPCL/Raw-M, cPCL/acid-oxidation MWNTs (AO-M) and cPCL/PEG grafted MWNTs (PEG-M) were obtained, and the mechanical, electrical and shape memory properties were further investigated. The influence of in vitro degradation on their shape memory and mechanical properties was also evaluated. The methyl thiazolyl tetrazolium (MTT) assay was performed to estimate their biocompatibility. The results displayed that these nanocomposites could perform favorable shape memory recovery both in hot water at 55 °C and in electric field with 50 V applied voltage. In addition, compared with cPCL/Raw-M and cPCL/AO-M, cPCL/PEG-M composite possessed more favorable properties such as mechanical, biocompatible, and electroactive shape memory functions. Therefore, the nanocomposite may be potential for application as smart bioactuators in biomedical field.

Actively targeted delivery of anticancer drug to tumor cells by redox-responsive star-shaped micelles.

In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery.

Controlled green tea polyphenols release from electrospun PCL/MWCNTs composite nanofibers.

Poly(ɛ-caprolactone)/multi-walled carbon nanotubes (PCL/MWCNTs) composite nanofibers with various content of green tea polyphenols (GTP) were successfully fabricated via an electrospinning technology to maintain the chemical structural stability of GTP. The non-covalent interaction between MWCNTs and GTP was measured by UV-vis spectrophotometer and FT-IR. The topographical features of the nanofibers were characterized by scanning electron microscopy (SEM). The dispersibility of MWCNTs and the distribution of GTP in nanofibers were observed by transmission electron microscopy (TEM) and laser scanning confocal microscope (LSCM), respectively. In vitro degradation was also characterized in terms of the morphological change and the mass loss of the nanofiber meshes. In vitro GTP release behavior was investigated in phosphate-buffered solution (PBS) at 37°C. Alamar blue assays were performed to estimate the cytotoxicity of the nanofibers with normal osteoblast cells and the antiproliferative effects to A549 and Hep G2 tumor cells. The results exhibited that the GTP-loaded composite nanofibers possessed a significant inhibition effect to tumor cells. Therefore, GTP, as a multifunctional drug, encapsulated into polymer composite nanofibers, must have broad application prospects in cancer therapy.

Redox-responsive polyanhydride micelles for cancer therapy

Biodegradable polyanhydrides possess unique features like those that they can predominantly undergo surface erosion, and the payloads can be released by a steady speed. However, there is little work that has been published to describe the polyanhydride micelles with redox-responsiveness as a nanocarrier for drug delivery. In this study, we develop one type of new amphiphilic polyanhydride copolymer containing disulfide bonds between the hydrophilic and hydrophobic segments. The copolymer can self-assemble into stable micelles with well-defined core-shell structure and a uniform size distribution with an average diameter of 69 nm. The disassembly behaviors of the micelles triggered by glutathione are evaluated from the changes of the micellar size, morphology and molecular weight. An approximate zero-order in vitro drug release mode with a fast speed can be achieved in a reducing and acid environment similar with that of tumor cells. In vitro cytotoxicity analysis demonstrate that the Cur-loaded micelles are of great efficiency in inhibiting the growth of cancer cells due to the rapidly intracellular delivery of therapeutic agent. Both the qualitative and quantitative results of the antitumor activity in 4T1 tumor-bearing BALB/c mice reveal that the redox-responsive micelles have a more significant therapeutic effect to artificial solid tumor compared to the redox-insensitive micelles. This study provides a new insight into the biomedical application of polyanhydrides in drug delivery.

Size Changeable Nanocarriers with Nuclear Targeting for Effectively Overcoming Multidrug Resistance in Cancer Therapy

A size changeable polymer micelle system with a dual shell, which increases in size under acidic pH conditions and is altered to smaller micelles, triggered by intracellular glutathione (GSH), is successfully developed. It is capable of direct delivering anticancer drugs to the nucleus of multidrug resistance (MDR) tumor cells for highly effective combating of drug resistant breast cancer.

Preparation and Characterization of a Novel Electrospun Spider Silk Fibroin/ Poly(D,L-lactide) Composite Fiber

In the paper, we successfully prepared spider silk fibroins (Ss)/poly( d, l-lactide) (PDLLA) composite fibrous nonwoven mats for the first time to the best of our knowledge. The morphology of the fibers was observed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The secondary structure change of the spidroin before and after electrospinning was characterized using Fourier transform infrared spectroscopy (FT-IR). Herein, a qualitative analysis of the conformational changes of the silk protein was performed by analyzing the FT-IR second-derivative spectra, from which quantitative information was obtained via the deconvolution of the amide I band. A mechanical test was carried out to investigate the tensile strength and the elongation at break. A water contact angle (CA) measurement was also performed to characterize surface properties of the fibers. The cytotoxicity of electrospun PDLLA and Ss-PDLLA nonwoven fibrous mats was evaluated based on a CCL 81(Vero) cells proliferation study. The results showed that the hydrophilic and mechanical property of the composite fiber were improved by introducing spidroin.