Biomedical subjects

Q L Feng

Publications and source records attributed to Q L Feng.

14 recordsLinked to original sources

PubMed2004

Hierarchically biomimetic bone scaffold materials: nano-HA/collagen/PLA composite.

A bone scaffold material (nano-HA/ collagen/PLA composite) was developed by biomimetic synthesis. It shows some features of natural bone both in main composition and hierarchical microstructure. Nano-hydroxyapatite and collagen assembled into mineralized fibril. The three-dimensional porous scaffold materials mimic the microstructure of cancellous bone. Cell culture and animal model tests showed that the composite material is bioactive. The osteoblasts were separated from the neonatal rat calvaria. Osteoblasts adhered, spread, and proliferated throughout the pores of the scaffold material within a week. A 15-mm segmental defect model in the radius of the rabbit was used to evaluate the bone-remodeling ability of the composite. Combined with 0.5 mg rhBMP-2, the material block was implanted into the defect. The segmental defect was integrated 12 weeks after surgery, and the implanted composite was partially substituted by new bone tissue. This scaffold composite has promise for the clinical repair of large bony defects according to the principles of bone tissue engineering.

Animals↗

PubMed2003

Covalent immobilization of chitosan and heparin on PLGA surface.

Chitosan and heparin were covalently immobilized onto a poly(lactic acid-co-glycolic acid) (PLGA) surface using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC), N-hydroxysuccinimide (NHS) in a 2-morpholinoethane sulfonic acid (MES) buffer system. The properties of the modified PLGA surface and the control were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water contact angle of the modified film was greatly decreased and the element content on the surface of the films changed correspondingly. Platelet adhesion assay showed that blood compatibility of the chitosan/heparin modified film was improved while hepatocyte culture indicated that the cell compatibility of the modified film was enhanced.

Animals↗

PubMed2003

Crosslinked collagen/chitosan matrix for artificial livers.

Matrices composed of collagen and chitosan may create an appropriate environment for the regeneration of livers. In this study, we have prepared, characterized and evaluated a new collagen/chitosan matrix (CCM). The CCM was made by using crosslinking agent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) in N-hydroxysuccinimide (NHS) and a 2-morpholinoethane sulfonic acid (MES) buffer system. The chemical characteristics were evaluated by Fourier-transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The mechanical strength was measured by tensile tests. The platelet deposition and hepatocyte culture experiments show that CCM has excellent blood and cell compatibility. The results suggest that the CCM is a promising candidate matrix for implantable bioartificial livers.

Animals↗

PubMed2002

Mechanical properties of skeletal bone in gene-mutated stöpsel(dtl28d) and wild-type zebrafish (Danio rerio) measured by atomic force microscopy-based nanoindentation.

An atomic force microscopy (AFM)-based nanoindenter was used to evaluate the mechanical properties of skeletal bones in wild-type and gene-mutated zebrafish (Danio rerio), stöpsel(dtl28d). Both skeletons were isolated from adult zebrafish and tested under a load of 5 mN. It was found that stp/stp bone has a similar nanohardness but significantly greater elastic modulus compared with that of wild-type bone. The residual indenter impressions using AFM and the fracture surfaces of both bones using scanning electron microscopy were examined and showed that the bone of zebrafish becomes more brittle after the stp mutation. This first observation of the alteration of bone mechanical behavior by gene mutation in zebrafish system is of scientific and clinical relevance to many areas of study, such as bone fracture and fragility mechanisms in human heritable disorders and bone-materials fabrication via gene engineering.

Animals↗

PubMed2000

A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus.

To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO(3) and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag(+) treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag(+) treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag(+) ions.

Anti-Bacterial Agents↗

PubMed2000

Formation of calcium phosphate/collagen composites through mineralization of collagen matrix.

Several types of calcium phosphate/collagen composites, including noncrystalline calcium phosphate/collagen, poorly crystalline carbonate-apatite (PCCA)/collagen, and PCCA + tetracalcium phosphate/collagen composites, were prepared through the mineralization of collagen matrix. The type I collagen was presoaked with a PO(3-)(4) containing solution and then immersed in a Ca(2+) containing solution to allow mineral deposition. The solution of 0.56 M sodium dibasic phosphate (Na(2)HPO(4)) with a pH of nearly 14 was metastable and its crystallization produced Na(2)HPO(4) and sodium tripolyphosphate hexahydrate (Na(5)P(3)O(10)). 6H(2)O), leading to a controlled release of orthophosphate ions during the subsequent mineral precipitation. The development of the composites was investigated in detail. The mineral contributed up to 60-70% of the weight of the final composites. The strength and Young's modulus of the composites in tensile tests overlapped the lower range of values reported for bone. When implanted in muscle tissue, the composite showed biodegradability that was partly through a multinucleated giant cell mediated process. In a bone explant culture model it was observed that bone-derived cells deposited mineralizing collagenous matrix on the composite.

Animals↗

PubMed1999

Spruce budworm (Choristoneura fumiferana) juvenile hormone esterase: hormonal regulation, developmental expression and cDNA cloning.

We have used the differential display of mRNAs technique to identify Choristoneura fumiferana genes that are induced by juvenile hormone I (JH I). Of the six PCR products identified, one bound to a 2.8-kb mRNA from CF-203 cells whose abundance increased when the cells were grown in the presence of JH I. The same 2.8-kb mRNA decreased to undetectable levels when the CF-203 cells were grown in the presence of 20-hydroxyecdysone (20E). The PCR fragment probe also detected a 2.8-kb mRNA in the C. fumiferana larval tissues. This 2.8-kb mRNA was present on the first day of the first, third, fourth, fifth and sixth larval and pupal stadia, but was conspicuously absent on the first day of the second larval stadium, as well as during the intermolt periods of the first to fifth instar larval stages. In the sixth instar larvae the 2.8-kb mRNA was detected in the fat body, epidermis and midgut during the intermolt period. The PCR fragment was used as a probe to screen a cDNA library. The deduced amino acid sequence of this 2.8-kb cDNA clone showed similarity with the deduced amino acid sequences of Heliothis virescens juvenile hormone esterases (HvJHE). The deduced amino acid sequence of the cDNA clone contained all five functional motifs that are present in most of esterases, proteases and lipases. The cDNA clone was expressed in the baculovirus expression system, producing a protein that showed JHE activity.

Amino Acid Sequence↗

PubMed1999

Glutathione S-transferase from the spruce budworm, Choristoneura fumiferana: identification, characterization, localization, cDNA cloning, and expression.

A 23-kDa protein that was present at higher levels in diapausing 2nd instar larvae than in feeding 2nd instar larvae of Choristoneura fumiferana was purified, and polyclonal antibodies were raised against this protein. The antibodies were subsequently used to screen a cDNA library that was constructed using RNA from 2nd instar larvae. Eight identical cDNA clones were isolated. The cDNA clone had a 665-bp insert and the longest open reading frame coded for a 203-amino acid protein with a predicted molecular mass of 23.37 kDa. The deduced amino acid sequence showed high similarity to glutathione S-transferases and therefore, the cDNA clone was named C. fumiferana glutathione S-transferase (CfGST). Identity of CfGST was confirmed by using affinity-purification as well as enzyme activity assay. CfGST was closer in similarity to insect GST2 members than GST1 members. The apparent Vmax of the purified CfGST towards the substrates glutathione and 1-chloro-2,4-dinitrobenezene (CDNB) were similar. However, the enzyme had a three-fold higher affinity towards CDNB than glutathione. Analyses using Northern blot, immunoblot and immunocytochemistry demonstrated that the fat body was the major tissue where the enzyme was synthesized and stored. Higher levels of CfGST protein were present in diapausing 2nd instar larvae compared to feeding 2nd and 6th instar larvae, suggesting that besides detoxification CfGST may have other roles during insect development that are not readily apparent at present. The CfGST cDNA was expressed in a recombinant baculovirus expression system and an active enzyme was produced.

Amino Acid Sequence↗

PubMed1998

Tissue response to nano-hydroxyapatite/collagen composite implants in marrow cavity.

The tissue response to a nano-hydroxyapatite/collagen composite implanted in a marrow cavity was investigated by histology and scanning electron microscopy. A Knoop microhardness test was performed to compare the mechanical behavior of the composite and bone. The ultrastructural features of the composite, especially the carbonate-substituted hydroxyapatite with low crystallinity and nanometer size, made it a bone-resembling material. It was bioactive, as well as biodegradable. At the interface of the implant and marrow tissue, solution-mediated dissolution and giant cell mediated resorption led to the degradation of the composite. Interfacial bone formation by osteoblasts was also evident. The process of implant degradation and bone substitution was reminiscent of bone remodeling. The composite can be incorporated into bone metabolism instead of being a permanent implant. For lack of the hierarchical organization similar to that of bone, the composite exhibited an isotropic mechanical behavior. However, the resistance of the composite to localized pressure could reach the lower limit of that of the femur compacta.

Animals↗

PubMed1998

Identification and developmental expression of the mitochondrial phosphate transport protein gene from the spruce budworm, Choristoneura fumiferana.

Phosphate transport protein (PTP) is a mitochondrial inner membrane protein responsible for the translocation of inorganic phosphate into the mitochondrial matrix. A full length cDNA clone encoding the PTP was isolated from the spruce budworm, Choristoneura fumiferana. The deduced amino acid sequence of the longest ORF of CfPTP cDNA showed high similarity with the amino acid sequences of PTPs cloned from several species. Phylogenetic tree analysis indicated that CfPTP occupied an intermediate position between vertebrates on the one side and yeast and nematodes on the other side. Studies on the developmental expression of CfPTP mRNA showed that higher levels of mRNA were present during the feeding and growing stages than during molting periods.

Amino Acid Sequence↗

PubMed1998

Antimicrobial effects of metal ions (Ag+, Cu2+, Zn2+) in hydroxyapatite.

The antimicrobial ceramics (AC) based on hydroxyapatite (HA) were made in a wet chemical process with additions of AgNO3, Cu(NO3)2. 3H2O and Zn(NO3)2. 6H2O. The ACs were composed of metal-ion substituted hydroxyapatite and nitrate-apatite, which was identified by X-ray diffraction. The viable count and turbidity measurement was adopted to observe the antimicrobial effects of the various ACs. The aerobic Escherichia coli was used in the study. An obvious antimicrobial effect against E. coli was observed in Ag+ AC. In contrast to Ag+ AC, it was difficult to ascertain any bactericidal effect in the case of Cu2+ and Zn2+ AC. The bactericidal effect of Ag+ was observed using a dialysis tube experiment. This suggests that Ag+ dissolved out and reacted with E. coli, thus inhibiting its growth.

Journal Article↗

PubMed1997

Highly adhesive hydroxyapatite coatings on titanium alloy formed by ion beam assisted deposition.

A compact crystalline hydroxyapatite coating on Ti-6Al-4V substrate with an atomic intermixed coating/substrate interface about 27 nm in width was synthesized by ion beam assisted deposition (IBAD) and a following post-treatment. The coating after post-treatment was identified by X-ray diffraction as crystalline hydroxyapatite. The interface between coatings and substrates was studied by Auger electron spectroscopy. The adhesive strength between coatings and substrates was measured by scratch tester. The results showed that the adhesive strength of IBAD coatings is nearly twice that of ion beam sputtered coatings. The study also showed that coatings prepared by IBAD eliminated the interfacial deficiencies existing in plasma-sprayed coatings.

Journal Article↗

PubMed1997

Microstructure and micromechanical properties of the mid-diaphyses of human fetal femurs.

The microstructure, composition and the micromechanical properties across the thickness of femoral mid-diaphyses from 14 to 26 week human fetuses have been investigated. Scanning electron microscopy and transmission electron microscopy were employed to examine structural changes with maturation. The fetal bones consist of layers of woven bone. From young to old fetuses and from outer to inner bone layers, the collagen fibrils become more cross-linked, densely packed and change from disordered to an ordered arrangement. The collagen fibril bundles are also more preferentially oriented and change from a chiefly circumferential to longitudinal direction. The sizes of the apatite crystals also increase with age. The Ca/P ratio remains constant around 1.55 for all the bone layers except the outmost layer which is lower than 1.2. An nano-indenter was used to evaluate the microhardness and elastic modulus of each bone layer. The increase of microhardness and elastic modulus correlates with the maturation of bone. The mechanical properties of the mid-diaphyses of human fetal femurs are anisotropic, which is due to the preferential orientation of collagen fibrils.

Collagen↗

PubMedDate not supplied

Microstructural investigation of the early external callus after diaphyseal fractures of human long bone.

Microstructures of the early external callus after diaphyseal fractures of human long bone were investigated by using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. It was found that the main structural framework of the human early callus consists of disordered, mineralized collagen fibrils with a small fraction of regions of ordered collagen fibrils. X-ray diffraction analyses show that hydroxyapatite containing some carbonate impurity has been the dominant crystalline phase in the human early callus. In addition, a small amount of brushite phase was detected. Selected area diffraction analyses indicated that hydroxyapatite microcrystals were embedded in microfibrils with a diameter of 4.5 nm and well-banded fibrils, whereas brushite particles of 15-20 nm in an irregular shape were located in the noncollagenous organic matter around the nonmineralized, ordered collagen fibrils. The spatial distribution of the brushite particles in the human early callus was for the first time determined. The brushite particles probably serve as the reservoir of calcium and phosphate ions for subsequent mineralized periods rather than the precursor of hydroxyapatite.

Bony Callus↗