Yuanming Zhang

Interactions between solubilized polymer molecules and blood components

In biomedical field, a variety of natural or synthetic polymers are being exponentially developed and used in vivo to improve human health. In practical applications, these biopolymers would enter blood circulation directly or indirectly, positively or passively, rapidly or slowly. Blood is a special tissue of human body, which fulfills many important missions to sustain normal metabolism. The contact with blood of the biopolymers, which are seen as foreign substances by the body, would be harmful or even instantaneously lethal, depending on the nature and the dose of the biopolymers administered. Therefore, it is critical to clearly understand the potential influences of the foreign polymers on blood before the polymers are applied from the lab to bedside. In this review, we discuss the recent studies on the interactions of foreign, solubilized polymer molecules (excluding formed polymer materials) with blood constituents (red blood cells, white blood cells, platelets, plasma proteins, etc.), to gain insight into the potential in vivo applications of the biopolymers in the biomedical field.

Therapeutic efficacy of antibiotic-loaded gelatin microsphere/silk fibroin scaffolds in infected full-thickness burns

Despite advances in burn treatment, burn infection remains a major cause of morbidity and mortality. In this study, an antibacterial silk fibroin (SF) scaffold for burn treatment was designed; gelatin microspheres (GMs) were impregnated with the antibiotic gentamycin sulfate (GS), and the GS-impregnated GMs were then embedded in a SF matrix to fabricate GS/GM/SF scaffolds. The developed GS/GM/SF scaffolds could serve as a dermal regeneration template in full-thickness burns. The average pore size and porosity of the GS/GM/SF scaffolds were 40-80 μm and 85%, respectively. Furthermore, the drug release rate of the scaffolds was significantly slower than that of either GS/GM or GS/SF scaffolds. And the composite scaffold exhibited stronger antimicrobial activities against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Hence, we evaluated the wound-healing effects and antibacterial properties of the GS/GM/SF scaffolds in a rat full-thickness burn infection model. Over 21 days, the GS/GM/SF scaffolds not only significantly reduced burn infection by P. aeruginosa but also accelerated the regeneration of the dermis and exhibited higher epithelialization rates than did GS/SF and SF scaffolds. Thus, GS/GM/SF scaffolds are potentially effective for treatment of full-thickness infected burns, and GS/GM/SF scaffolds are a promising therapeutic tool for severely burned patients.

Preparation and properties of cellulose nanocrystals reinforced collagen composite films.

Collagen films have been widely used in the field of biomedical engineering. However, the poor mechanical properties of collagen have limited its application. Here, rod-like cellulose nanocrystals (CNCs) were fabricated and used to reinforce collagen films. A series of collagen/CNCs films were prepared by collagen solution with CNCs suspensions homogeneously dispersed at CNCs: collagen weight ratios of 1, 3, 5, 7, and 10. The morphology of the resulting films was analyzed by scanning electron microscopy (SEM), the enhancement of the thermomechanical properties of the collagen/CNCs composites were demonstrated by thermal gravimetric analysis (TGA) and mechanical testing. Among the CNCs contents used, a loading of 7 wt % led to the maximum mechanical properties for the collagen/CNCs composite films. In addition, in vitro cell culture studies revealed that the CNCs have no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. We conclude that the incorporation of CNCs is a simple and promising way to reinforce collagen films without impairing biocompatibility. This study demonstrates that the composite films show good potential for use in the field of skin tissue engineering.

Controlled release and targeted delivery to cancer cells of doxorubicin from polysaccharide-functionalised single-walled carbon nanotubes

Carboxyl single-walled carbon nanotubes (SWNTs) were used to construct an innovative drug delivery system by modification with chitosan (CHI) to enhance water solubility and biocompatibility. Hyaluronan (HA), as the target ligand for CD44, was bound to the CHI layer to selectively kill cancer cells. To achieve a new treatment strategy for cancer, the drug delivery system was loaded with the anticancer drug doxorubicin hydrochloride (DOX). The data showed that the system loaded with DOX with zeta potentials of 8.52 ± 0.12 mV at pH 7.4 and 12.53 ± 0.23 mV at pH 5.5 had high drug-loading efficiency, reaching 107.73 ± 0.67%. It also exhibited sustained and controlled drug-release, depending on pH; it released less than 10% at pH 7.4 but nearly 85% at pH 5.5 after 72 h. Cell viability results indicated that the drug delivery system effectively killed HeLa cells while it had lower cytotoxicity against fibroblasts. Combined histological examinations and blood property analyses demonstrated that it did not cause severe damage to vital organs in SD rats. Thus, this drug delivery system may provide a high therapeutic efficacy for cancer, while minimising adverse side effects.

Preparation and properties of PLGA nanofiber membranes reinforced with cellulose nanocrystals

Although extensively used in the fields of drug-carrier and tissue engineering, the biocompatibility and mechanical properties of polylactide-polyglycolide (PLGA) nanofiber membranes still limit their applications. The objective of this study was to improve their utility by introducing cellulose nanocrystals (CNCs) into PLGA nanofiber membranes. PLGA and PLGA/CNC composite nanofiber membranes were prepared via electrospinning, and the morphology and thermodynamic and mechanical properties of these nanofiber membranes were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The cytocompatibility and cellular responses of the nanofiber membranes were also studied by WST-1 assay, SEM, and confocal laser scanning microscopy (CLSM). Incorporation of CNCs (1, 3, 5, and 7 wt.%) increased the average fiber diameter of the prepared nanofiber membranes from 100 nm (neat PLGA) to ∼400 nm (PLGA/7 wt.% CNC) and improved the thermal stability of the nanofiber membranes. Among the PLGA/CNC composite nanofiber membranes, those loaded with 7 wt.% CNC nanofiber membranes had the best mechanical properties, which were similar to those of human skin. Cell culture results showed that the PLGA/CNC composite nanofiber membranes had better cytocompatibility and facilitated fibroblast adhesion, spreading, and proliferation compared with neat PLGA nanofiber membranes. These preliminary results suggest that PLGA/CNC composite nanofiber membranes are promising new materials for the field of skin tissue engineering.

In vitro and in vivo evaluation of a novel collagen/cellulose nanocrystals scaffold for achieving the sustained release of basic fibroblast growth factor:

Tissue-engineered dermis is thought to be the best treatment for skin defects; however, slow vascularization of these biomaterial scaffolds limits their clinical application. Exogenous administration of angiogenic growth factors is highly desirable for tissue regeneration. In this study, biodegradable gelatin microspheres (GMs) containing basic fibroblast growth factor (bFGF) were fabricated and incorporated into a porous collagen/cellulose nanocrystals (CNCs) scaffold, as a platform for long-term release and consequent angiogenic boosting. The physicochemical properties of these scaffolds were examined and the in vitro release pattern of bFGF from scaffolds was measured by ELISA. Collagen/CNCs scaffolds with and without bFGF-GMs were incubated with human umbilical vein endothelial cells for 1 week, results showed that the scaffolds with bFGF-GMs significantly augmented cell proliferation. Then, four different groups of scaffolds were implanted subcutaneously into Sprague–Dawley rats to study angiogenesis in vivo via macroscopic observation, and hematoxylin and eosin and immunohistochemical staining. The results suggested that the collagen/CNCs/bFGF-GMs scaffolds had a significantly higher number of newly formed and mature blood vessels, and the fastest degradation rate. This study demonstrated that collagen/CNCs/bFGF-GMs scaffolds have great potential in skin tissue engineering.

Preparation and characterisation of vancomycin-impregnated gelatin microspheres/silk fibroin scaffold

A type of antibacterial silk fibroin (SF) scaffold was developed and characterised as a potential functional wound dressing for acute trauma treatment. To achieve this, SF solution was mixed with previously fabricated vancomycin (Vm)-loaded gelatin (G) microspheres, followed by a freeze-drying step. Some physical and antimicrobial properties of the prepared Vm/G/SF scaffolds were investigated and the results demonstrated that the average pore size and porosity of the composite scaffold were 60–80 μm and 75%, respectively. The compressive stress and compressive modulus of Vm/G/SF scaffold were 140 and 468 KPa, respectively. Compared with Vm/G microspheres and Vm/SF scaffold, the Vm/G/SF scaffold has slower release rate of Vm. In addition, the Vm release rate of Vm/G/SF scaffold matched well with the degradation rate of SF scaffold. With respect to the antimicrobial effect, the results showed that the Vm/G/SF scaffold had good antimicrobial activity against Staphylococcus aureus (gram-positive), which is a gram-positive bacteria commonly found in infected wounds.

Synthesis, characterisation and preliminary investigation of the haemocompatibility of polyethyleneimine-grafted carboxymethyl chitosan for gene delivery.

The development of safe and efficient gene carriers is the key to the clinical success of gene therapy. In the present study, carboxymethyl chitosan (CMCS) was prepared by chitosan (CS) alkalisation and carboxymethylation reactions. Then polyethyleneimine (PEI) was grafted to the backbone of CMCS by an amidation reaction. The CMCS-PEI copolymer showed strong complexation capability with DNA to form nanoparticles, and achieved lower cytotoxicity and higher transfection efficiency compared with PEI (25 kDa) towards 293T and 3T3 cells. Moreover, the haemocompatibility of the CMCS-PEI copolymer was investigated through the aggregation, morphology and lysis of human red blood cells (RBCs), along with the impact on the clotting function with activated partial thromboplastin time (APTT), prothrombin time (PT) and thromboelastographic (TEG) assays. The results demonstrated that the CMCS-PEI copolymer with a concentration lower than 0.05 mg/mL had little impact on the aggregation, morphology or lysis of RBCs, or on blood coagulation. Therefore, the copolymer may be a strong alternative candidate as an effective and safe non-viral vector.

Collagen-cellulose nanocrystal scaffolds containing curcumin-loaded microspheres on infected full-thickness burns repair

Burn infection is a serious problem that delays wound healing and leads to death. Curcumin (Cur) has been shown to exhibit antioxidant, anti‐inflammatory, antimicrobial and anticarcinogenic activity. However, its instability, extremely low aqueous solubility and bioavailability in physiological fluids may make it difficult to maintain local Cur concentrations above the minimum inhibitory concentration for burn infection treatment. The objective of this study was to construct complexes of Cur/gelatin microspheres (GMs) and porous collagen (Coll)‐cellulose nanocrystals (CNCs) composite scaffolds for full‐thickness burn infection treatment. The Cur/GMs/Coll‐CNCs scaffolds had high porosity, available pore size, and a long and sustained Cur release profile. Furthermore, the composite scaffold exhibited remarkably strong antibacterial activity. Hence, we evaluated the wound‐healing effects and antibacterial properties of Cur/GMs/Coll‐CNCs scaffolds in a rat full‐thickness burn infection model. The Cur/GMs/Coll‐CNCs scaffold was able to prevent not only local inflammation but also accelerated dermis regeneration. Thus, we conclude that Cur/GMs/Coll‐CNCs scaffolds can act as an effective dermal regeneration template for full‐thickness burn wound infection healing in rats models. Copyright

Interaction of Polyethyleneimines with Fibrinogen and Erythrocyte Membrane

For any administered or implanted biomaterials in contact with blood tissue, they first and unavoidably encounter plasma components and blood cell membranes, and immediately strong or weak interactions between them will be initiated. Therefore, the safety issue of the biomaterials for blood tissue should be given a full consideration. In this study, the effects of the gene carrier polyethyleneimines (PEIs) differing in molecular weight and shape (branched or linear) on plasma proteins and blood cell membranes were investigated in detail. On one hand, the structure, conformation, and biofunction of fibrinogen as an important plasma protein were examined by UV-vis, fluorescence and circular dichroism spectroscopy, and fibrin polymerization test, respectively. Furthermore, the rheological behavior of whole blood containing the PEIs was also evaluated. On the other hand, the morphology, surface roughness, membrane proteins, and enzyme activity on erythrocyte membrane after the PEIs-treatment were also examined by using atomic force microscopy, electrophoresis, and enzyme activity test, respectively. The results reveal that, the PEIs alter the struture and conformation of fibrinogen and then modify the fibrin polymerization process. As a result, the clotting function of the PEIs-containing blood is also affected. Additonally, the PEIs also have severe impact on the morphology, roughness, and membrane proteins, and inhibit acetylcholinesterase activity of erythrocyte membrane. These findings shed light toward the design of safe PEIs and other biomedical materials by comprehensive preconsideration of their interactions with plasma proteins and blood cell membranes.