Novel brain-targeted nanomicelles for anti-glioma therapy mediated by the ApoE-enriched protein corona in vivo.

BACKGROUND: The interactions between nanoparticles (NPs) and plasma proteins form a protein corona around NPs after entering the biological environment, which provides new biological properties to NPs and mediates their interactions with cells and biological barriers. Given the inevitable interactions, we regard nanoparticle‒protein interactions as a tool for designing protein corona-mediated drug delivery systems. Herein, we demonstrate the successful application of protein corona-mediated brain-targeted nanomicelles in the treatment of glioma, loading them with paclitaxel (PTX), and decorating them with amyloid ß-protein (Aß)-CN peptide (PTX/Aß-CN-PMs). Aß-CN peptide, like the Aß1-42 peptide, specifically binds to the lipid-binding domain of apolipoprotein E (ApoE) in vivo to form the ApoE-enriched protein corona surrounding Aß-CN-PMs (ApoE/PTX/Aß-CN-PMs). The receptor-binding domain of the ApoE then combines with low-density lipoprotein receptor (LDLr) and LDLr-related protein 1 receptor (LRP1r) expressed in the blood-brain barrier and glioma, effectively mediating brain-targeted delivery. METHODS: PTX/Aß-CN-PMs were prepared using a film hydration method with sonication, which was simple and feasible. The specific formation of the ApoE-enriched protein corona around nanoparticles was characterized by Western blotting analysis and LC-MS/MS. The in vitro physicochemical properties and in vivo anti-glioma effects of PTX/Aß-CN-PMs were also well studied. RESULTS: The average size and zeta potential of PTX/Aß-CN-PMs and ApoE/PTX/Aß-CN-PMs were 103.1 nm, 172.3 nm, 7.23 mV, and 0.715 mV, respectively. PTX was efficiently loaded into PTX/Aß-CN-PMs, and the PTX release from rhApoE/PTX/Aß-CN-PMs exhibited a sustained-release pattern in vitro. The formation of the ApoE-enriched protein corona significantly improved the cellular uptake of Aß-CN-PMs on C6 cells and human umbilical vein endothelial cells (HUVECs) and enhanced permeability to the blood-brain tumor barrier in vitro. Meanwhile, PTX/Aß-CN-PMs with ApoE-enriched protein corona had a greater ability to inhibit cell proliferation and induce cell apoptosis than taxol. Importantly, PTX/Aß-CN-PMs exhibited better anti-glioma effects and tissue distribution profile with rapid accumulation in glioma tissues in vivo and prolonged median survival of glioma-bearing mice compared to those associated with PMs without the ApoE protein corona. CONCLUSIONS: The designed PTX/Aß-CN-PMs exhibited significantly enhanced anti-glioma efficacy. Importantly, this study provided a strategy for the rational design of a protein corona-based brain-targeted drug delivery system. More crucially, we utilized the unfavorable side of the protein corona and converted it into an advantage to achieve brain-targeted drug delivery.

The in vivo characterization of electrospun heparin-bonded polycaprolactone in small-diameter vascular reconstruction.

OBJECTIVE: To evaluate the possibility of using heparin-bonded polycaprolactone grafts to replace small-diameter arteries. METHODS: Polycaprolactone was bonded with heparin. The activated partial thromboplastin time of heparin-bonded polycaprolactone grafts was determined in vitro. Small-diameter grafts were electrospun with heparin-bonded polycaprolactone and polycaprolactone and were implanted in dogs to substitute part of the femoral artery. Angiography was used to investigate the patency and aneurysm of the grafts after transplantation. After angiography, the patent grafts were explanted for histology analysis. The degradation of the grafts and the collagen content of the grafts were measured. RESULTS: Activated partial thromboplastin time tests in vitro showed that heparin-bonded polycaprolactone grafts exhibit obvious anticoagulation. Arteriography showed that two heparin-bonded polycaprolactone and three polycaprolactone grafts were obstructed. Other grafts were patent, without aneurysm formation. Histological analysis showed that the tested grafts degraded evidently over the implantation time and that the luminal surface of the tested grafts had become covered by endothelial cells. Collagen deposition in heparin-bonded polycaprolactone increased with time. There were no calcifications in the grafts. Gel permeation chromatography showed the heparin-bonded polycaprolactone explants at 12 weeks lose about 32% for Mw and 24% for Mn. The collagen content on the heparin-bonded polycaprolactone grafts increased over time. CONCLUSION: This preliminary study demonstrates that heparin-bonded polycaprolactone is a suitable graft for small artery reconstruction. However, heparin-bonded polycaprolactone degrades more rapidly than polycaprolactone in vivo.

Giant cell tumour of bone in the appendicular skeleton: an analysis of 276 cases.

This retrospective study analyzed 276 cases of giant cell tumour of bone in the appendicular skeleton of patients first diagnosed and treated at the Orthopaedic Department of the West China Hospital in Sichuan University between 1988 and 2007. Fifty-eight percent of the tumours involved the knee region. The most common primary treatment was curettage (162 patients) combined with adjuvant local therapy. The effects of bone cement (PMMA), high-speed burring, electro- cauterization, liquid nitrogen, and phenol on the recurrence rate were also analyzed. The differences in local recurrence rates were analyzed between giant-cell tumours confined to bone (Campanacci grades I and II) and giant-cell tumours with extraosseous extension (Campanacci grade III) treated with intralesional curettage. The recurrence rate of patients who received the first treatment at our institution was 11.2%. Recurrence was observed in 31 cases and multiple recurrences were observed in 5 cases. Treatment included intralesional curettage (173%), marginal excision (143%), wide excision (1.9%), or radical resection (0%). Metastases, which mainly involved the lung, occurred in 6 cases (2.2%). There was a significantly lower recurrence rate (p = 0.004) following intralesional curettage combined with high-speed burring (n = 102) as compared with intralesional curettage without high-speed burring (n = 60). Although the efficacy of liquid nitrogen and electrocauterization did not reach significance, they seem to have a similar effect to high-speed burring. Therefore, we recommend high-speed burring as a necessary adjuvant therapy. The combination of all adjuvants (burring, liquid nitrogen, and electro-cauterization) is recommended as a standard treatment. Cement filling of the cavity after curettage was not widely used in this series, but its merits have been reported in several studies; we therefore recommend that cement filling should be added to the adjuvants to be used after burring, liquid nitrogen and/or electrocauterization.

[Application of n-HA/PA66 composite artificial vertebral body in anterior reconstruction of lower cervical spine fracture and dislocation].

OBJECTIVE: To initially evaluate the application of artificial vertebra of n-HA/PA66 in anterior reconstruction of lower cervical spine fracture and dislocation. METHODS: In this study, 84 patients with lower cervical spine fracture and dislocation received anterior cervical discectomy, spinal canal decompression or subtotal corpectomy, spinal canal decompression and reconstruction by n-HA/PA66 composite artificial vertebral body combined with plate instrumentation. Neurological function was followed up by improvement rate of Frankel and situations of the supporting body was observed by X ray and 3D-CT in 3, 12, 24 months postoperatively. The intervertebral height, physical arc (reflected by Cobb angle) and the locations and fusion rate of the supporting body were assessed in order to evaluate the stability of the cervical spine and alignment improvements. RESULTS: All the patients underwent operation successfully and were followed up for 6 to 24 months with an average of 12 months. The preoperative symptoms were improved to varying degrees. Imaging studies showed that in all cases graft fusion were achieved, and cervical alignments, intervertebral height, cervical spine stability and the locations of the artificial vertebral body were well maintained. No displacement and subsidence of the artificial vertebral body occurred. Postoperative immediate intervertebral height (2.4 ± 0.2) cm, preoperative intervertebral height (1.9 ± 0.1) cm, comparisons of the two groups was statistically significant (q = 2.48, P < 0.001). The immediate, 3 month, 1 year, 2 year period follow-up group intervertebral height was not statistically significant (P > 0.05). Preoperative Cobb angle was 9.8° ± 1.2°, postoperative immediate Cobb angle was 16.6° ± 1.2°, comparisons of the two groups was statistically significant (q = 14.25, P < 0.001). The immediate, 3 month, 1 year, 2 year period follow-up group Cobb angle was not statistically significant (P > 0.05). CONCLUSIONS: n-HA/PA66 artificial vertebral body can provide early cervical spine support and stability and effectively maintain the biological alignment and cervical intervertebral height. It has high rate of graft fusion and is convenient to observe by X-ray. Therefore, n-HA/PA66 can be taken as an ideal graft for anterior lower cervical spine fracture and dislocation operation, but further follow-up study is still required to evaluate the long-term effects.

[Repairing bone defect with nano-hydroxyapatite and polyamide 66 composite after giant cell tumor operations].

OBJECTIVE: To evaluate the clinical effectiveness and safety of using granular type nano-hydroxyapatite and polyamide 66 (n-HA/PA66) composite in repairing bone defects caused by giant cell tumors. METHODS: 48 patients with giant cell tumors, who underwent lesion curettage, inactivation and cavities fill-in with granular type n-HA/PA66 from December 2007 to May 2011, were followed up. Routine blood tests, liver and kidney functions, serum calcium and phosphorus, and immunologic parameters were examined before and after the surgeries. Radiological examinations were carried out 1 week and 1, 3, 6 and 12 months post operations to monitor the bone repairing process. The n-HA/ PA66 in bone issues was detected with hematoxylin-eosin staining. RESULTS: 45 patients completed the follow-up. No significant abnormalities in routine blood tests, serum calcium and phosphorus, and immunologic parameters were found pre- and post-operations. Nor abnormal liver and kidney functional lesions were identified. The radiological examination showed gradual increase in the density of the focal zone after bone implanting operations. The bone density of the implanted areas got close to normal 1 year after operations. The histological examination found that osteoblasts grew into the hole of n-HA/PA66; calcium was deposited on the materials; and large amount of osteocytes inlaid into the composite. The composite was integrated into new bone and surrounding tissues. CONCLUSION: n-HA/PA66 has good biocompatibility and biological safety. It also has good osteoconduction and osteogenesis activity. The n-HA/PA66 composite is one perfect bone repair material.

CEC separation of ofloxacin enantiomers using imprinted microparticles prepared in molecular crowding conditions.

Molecular crowding is a new concept to obtain molecularly imprinted polymers (MIPs) with greater capacity and selectivity, which could shift the equilibrium of a print molecule reacting with functional monomers in the direction of complex formation side. In this work, molecular crowding agent was first applied to the preparation of MIPs microparticles by precipitation polymerization. A new system of molecular crowding surrounding was developed, composed of polystyrene and tetrahydrofuran, in the presence of the template (S)-ofloxacin. Partial filling capillary electrochromatography (CEC) was utilized to evaluate imprinting effect of the resulting microparticles by chiral separations of ofloxacin. Some important parameters in the preparation, i.e. template to monomer ratio, influence of cross-linking monomers and functional monomer composition on the CEC separation of MIP microparticles were investigated. Baseline separation of ofloxacin (R(s) =1.53) was obtained under optimized conditions and the highest theory plate of the later eluent (S)-ofloxacin was 5400. The textural and morphological parameters for imprinted particles, such as Brunauer-Emmett-Teller surface areas, pore volumes and pore size distributions have also been determined. Compared to the MIP microparticle prepared by conventional precipitation polymerization, the (S)-ofloxacin-imprinted particles formed under molecular crowding conditions showed higher selectivity (α=1.09) and separation efficiency (<25 min) in the CEC mode.

[The design, preparation and compressive strength testing of interbody fusion cages made from a composite of multi-amino acid copolymer/tri-calcium phosphate].

This research was to design and prepare interbody fusion cages using composite materials of multi-amino acid copolymer/tri-calcium phosphate (MAACP/TCP) and to test compressive strength of the cages. 16 specimens of C3-4 segments from female adult goats were scanned by X-ray to exclude disease of cervical spine, and then anatomical data were measured, i. e. disc space height of C3-4 segment (DSH), sagittal diameter of C3 lower endplate (SDLE3), sagittal diameter of C4 upper endplate (SDUE4), coronary diameter of C3 lower endplate (CDLE3), and coronary diameter of C4 upper endplate (CDUE4). According to the anatomical data, we designed and prepared the interbody fusion cage using the composite of MAACP/TCP and titanium with the same sizes. The MAACP/TCP Cages were made with the method of injection molding and finish machining, and titanium Cages were made with machining. In the testing of compressive strength of Cages, the specimens were divided into three groups, tricortical iliac crest bone group (isolated from goats), MAACP/TCP Cage group and titanium Cage group. There were 8 specimens in every group with the same sizes, the length of 12 mm, the width of 10 mm, and the height of 6 mm. The compressive strength of all specimens was tested on a universal testing machine. The values of DSH, SDLE3, SDUE4, CDLE3 and CDUE4 were (4.78 +/- 0.17) mm, (15.06 +/- 0.53) mm, (12.46 +/- 0.44) mm, (14.47 +/- 0.51) mm and (12.15 +/- 0.65) mm, respectively. MAACP/TCP Cage was successfully designed and made with a compressive strength of 76.34 MPa, which was much higher than that of tricortical iliac crest bone (18.41 MPa). The maximal loading of universal testing machine was 50 000 N, so the compressive strength of titanium Cages, whose value should be more than 541.35 MPa, could not be tested precisely. It is feasible to make cages with MAACP/TCP composite, and the compressive strength of MAACP/TCP Cages was much higher than that of tricortical iliac crest bone isolated from goats.

[Biomechanical evaluation of immediate stability of biodegradable multi-amino acid copolymer/tri-calcium phosphate composite interbody Cages in a goat cervical spine model].

UNLABELLED: A new kind of Interbody Cage made of multi-amino acid copolymer/tri-calcium phosphate (MAACP/TCP) composite was designed, and the purpose of this study was to evaluate immediate stability of MAACP/TCP Cage in a goat cervical spine model (C3-4). After the motion segment C3-4 was tested intact, 27 goat cervical spines were divided into three groups randomly. There were four groups group A. MAACP/TCP Cage group (n = 9), group B2 titanium Cage group (n = 9), group C2 autologous tricortical iliac crest bone group (n = 9) and group D: intact group (n = 27). Different Cage groups were implanted after complete discectomy (C3-4) was performed. Then they were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method. The range of motion (ROM) and relative stiffness were calculated and compared between groups. In comparison to the intact motion segment, MAACP/TCP Cage showed a significantly (P < 0.05) lower ROM and a significantly (P < 0.05) higher relative stiffness in flexion and lateral bending. In comparison to the tricortical iliac crest bone graft, MAACP/TCP Cage showed a significantly (P < 0.05) lower ROM and a significantly (P < 0.05) higher relative stiffness in extension, flexion and lateral bending. There was no significant (P > 0.05) difference in the ROM and relative stiffness between MAACP/TCP Cage and titanium Cage in extension, flexion and lateral bending. In comparison to titanium Cage, MAACP/TCP Cage showed a significantly (P < 0.05) higher ROM and a significantly (P < 0.05) lower relative stiffness in rotation. CONCLUSION: MAACP/TCP Cage can provide enough immediate stability for cervical interbody fusion in a goat cervical spine model.

Experimental study on repair of large segmental bone defects of goat femur by nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer membrane tubes.

OBJECTIVE: The purpose of this study was to observe feasibility of nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer (n-CDHA-MAC) membrane tubes in repairing goat femurs' large defects. METHODS: Twelve goats were divided into two groups, whose femurs were created 30 mm segmental bone defects and then implants were performed. In experimental group, the bone defect of right femur was reconstructed by n-CDHA-MAC membrane tube, while left side was reconstructed by allogenic bone tube in control group. Every three goats were sacrificed at 4, 8, 16, 24 weeks after operation respectively. General observation, X-ray analysis, histology, Scanning electron microscope (SEM) examination and protein level comparison of BMP-2 were conducted to evaluate the effects of repairing segmental bone defects. RESULTS: All goats recovered well from anesthesia and surgical interventions. The radiographic evaluations showed that periosteal reaction outside of the membrane tubes and allogenic bone tubes were observed 4 weeks after surgery. At 16 weeks, callus was continuously increased in experimental group, which was more obvious than control group. At 24 weeks, callus outside of the membrane tubes connected together. Histologic evaluation showed fibro-cartilage callus was evolved into bony callus in experimental group, which was more obvious than control group at 8 and 16 weeks. The protein expression level of BMP-2 increased at 4, 8 weeks and peaked at 16 weeks in experimental groups. There were statistical differences at 8 and 16 weeks (P < 0.05). At each time point in 8, 16, 24 weeks after surgery, the bending stiffness, torsional stiffness and compressive strength of the two groups were similar, and there was no significant difference (P > 0.05). CONCLUSIONS: This novel surface degradation n-CDHA-MAC membrane tube has good ability to maintain enough membrane space, which can provide long-term and stable biomechanical support for large bone defects and integrate well with the surrounding bone.

Efficient Anti-Glioma Therapy Through the Brain-Targeted RVG15-Modified Liposomes Loading Paclitaxel-Cholesterol Complex.

BACKGROUND: Glioma is the most common primary malignant brain tumor with a dreadful overall survival and high mortality. One of the most difficult challenges in clinical treatment is that most drugs hardly pass through the blood-brain barrier (BBB) and achieve efficient accumulation at tumor sites. Thus, to circumvent this hurdle, developing an effectively traversing BBB drug delivery nanovehicle is of significant clinical importance. Rabies virus glycoprotein (RVG) is a derivative peptide that can specifically bind to nicotinic acetylcholine receptor (nAChR) widely overexpressed on BBB and glioma cells for the invasion of rabies virus into the brain. Inspired by this, RVG has been demonstrated to potentiate drugs across the BBB, promote the permeability, and further enhance drug tumor-specific selectivity and penetration. METHODS: Here, we used the RVG15, rescreened from the well-known RVG29, to develop a brain-targeted liposome (RVG15-Lipo) for enhanced BBB permeability and tumor-specific delivery of paclitaxel (PTX). The paclitaxel-cholesterol complex (PTX-CHO) was prepared and then actively loaded into liposomes to acquire high entrapment efficiency (EE) and fine stability. Meanwhile, physicochemical properties, in vitro and in vivo delivery efficiency and therapeutic effect were investigated thoroughly. RESULTS: The particle size and zeta potential of PTX-CHO-RVG15-Lipo were 128.15 ± 1.63 nm and -15.55 ± 0.78 mV, respectively. Compared with free PTX, PTX-CHO-RVG15-Lipo exhibited excellent targeting efficiency and safety in HBMEC and C6 cells, and better transport efficiency across the BBB in vitro model. Furthermore, PTX-CHO-RVG15-Lipo could noticeably improve the accumulation of PTX in the brain, and then promote the chemotherapeutic drugs penetration in C6luc orthotopic glioma based on in vivo imaging assays. The in vivo antitumor results indicated that PTX-CHO-RVG15-Lipo significantly inhibited glioma growth and metabasis, therefore improved survival rate of tumor-bearing mice with little adverse effect. CONCLUSION: Our study demonstrated that the RVG15 was a promising brain-targeted specific ligands owing to the superior BBB penetration and tumor targeting ability. Based on the outstanding therapeutic effect both in vitro and in vivo, PTX-CHO-RVG15-Lipo was proved to be a potential delivery system for PTX to treat glioma in clinic.

Biomechanical and histological evaluation of the application of biodegradable poly-L-lactic cushion to the plate internal fixation for bone fracture healing.

BACKGROUND: Internal plate fixation of fracture can provide favorable mechanical environment for fracture fragments. However, osteoporosis under the plate is often found, and refracture may occur after the plate is removed. There are two different opinions about the bone loss beneath the plate: first is the stress shielding effect brought by the rigid fixation, and the second is the insufficient blood supply of the bone caused by the placement of the plate. In this paper, we tried to achieve a favorable condition for the fracture healing by inserting a kind of biodegradable cushion, through which the stress shielding effect and the interruption of the bone blood supply could be relieved at the same time. METHODS: Animal models of internal fixation for tibia diaphyseal fracture with the placement of the poly-l-lactic (PLLA) cushion between the plate and the bone were established; a series of in vitro investigations and finite element (FE) analysis were performed to evaluate the effect of this new internal fixation system. FINDINGS: During both the initial and 50% healing periods, the extent of stress shielding of the fracture zone decreased due to the use of the PLLA cushion. Especially for the 50% healing stage, the insertion of the PLLA cushion on alleviating the stress shielding of the bone tissue between the inner two screws directly under the plate is more apparent than that at the initial healing period. Meanwhile, radiological and histological coloration results demonstrated sooner callus growth and better trabecular rearrangement of the fracture zone in the PLLA group with the degradation of the PLLA cushion during the healing periods. INTERPRETATIONS: This study showed that the use of the PLLA cushion at the initial period did not impair the stability of the whole system, which provides a favorable mechanical environment for the following fracture healing. On the other hand, its superiorities on alleviating stress shielding effect and interruption with the blood supply of the bone tissue beneath the plate contributed to the favorable fracture healing conditions in PLLA group with the degradation of the materials.

[Three-dimensional finite element analysis responsible to bone cement with customized prosthesis of proximal segmental femur].

OBJECTIVES: To create three-dimensional finite element models for the large defect of proximal femur and the customized prosthesis of proximal segmental defect femur, and to analyze the influence on the stress distribution of femur-cement after the intramedullary implantation of different stem length prostheses. METHODS: Three-dimensional finite element models were established for the large defect of proximal femur and proximal femoral segmental prostheses with different stem-lengths (140 mm, 120 mm, 100 mm, 80 mm and 60 mm). The influence on stress distribution of femur-cement was analyzed for the different stem-length prostheses implanted. RESULTS: The stress on bone cement gradually increased from proximal end to distal end, and reached its highest value near the tip of prostheses. The prostheses with stem lengths of 120 mm, 100 mm, 80 mm and 60 mm could bring the cement mantle stress to the value beyond the fatigue strength of cement. Only when the intramedullary stem-length of prosthesis was 140 mm, the stress on the cement mantle was under the fatigue strength of cement. CONCLUSION: The intramedullary stem of the proximal femoral segmental prosthesis must have enough length to decrease the stress on the cement mantle in order to avoid the prosthesis loosening.

[Preparation of liposomes containing extracts of Tripterygium wilfordii and evaluation of its stability].

OBJECTIVE: The liposomes containing extracts of Tripterygium wilfordii were prepared and the possibility of entrapment of complex chemicals by liposomes were studied. METHOD: The liposomes containing extracts of T. wilfordii were prepared by thin-film dispersion method, the effect of process parameters and composition of materials on the entrapment efficiency of the main components were studied. The stability of the liposomes dispersion was also evaluated. RESULT: The liposomes made by thin-film dispersion method were mostly small unilamellar vesicles and their particle size was 30 nm to approximately 50 nm. The optimum entrapment efficiency of tripterine and the total alkaloids were respectively 98.10% and 88.63% but the liposomes dispersion was unstable when kept at 4 degrees C. CONCLUSION: The complex chemicals can be entrapped by the liposomes, but its stability need to be improved furtherly.

Gene screening facilitates diagnosis of complicated symptoms: A case report.

Gene mutation has an important role in disease pathogenesis; therefore, genetic screening is a useful tool for diagnosis. The present study screened pathogenic genes, ectodysplasin A (EDA) and lamin A/C (LMNA), in a patient with suspected syndromic hearing impairment and various other symptoms including tooth and skin abnormalities. Large­scale sequencing of 438 deafness­associated genes and whole­genome sequencing was also performed. The present findings did not identify copy number variation and mutations in EDA; therefore, excluding the possibility of EDA­initiated ectodermal dysplasia syndrome. A synonymous mutation in LMNA, possibly due to a splicing abnormality, did not elucidate the pathogenesis of Hutchinson­Gilford progeria syndrome. Whole­genome sequencing revealed copy number variations or mutations in various candidate genes which may elucidate part of the symptoms observed. The copy number variations and mutations were also used to identify single nucleotide variations (SNVs) in crystallin mu (CRYM), RAB3 GTPase activating protein catalytic subunit 1 (RAB3GAP1) and Wnt family member 10A (WNT10A), implicated in deafness, hypogonadism and tooth/skin abnormalities, respectively. The importance of an existing SNV in CRYM and a novel SNV in RAB3GAP1 in pathogenesis remains to be further elucidated. The WNT10A p.G213S mutation was confirmed to be the etiological cause of tooth agenesis and ectodermal dysplasia as previously described. It was concluded that a mutation in WNT10A may be the reason for some of the symptoms observed in the patient; however, other genes may also be involved for other symptoms. The findings of the present study provide putative gene mutations that require further investigation in order to determine their roles in pathogenesis.

All-polyethylene tibial components in distal femur limb-salvage surgery: a finite element analysis based on promising clinical outcomes.

BACKGROUND: Whether all-polyethylene tibial (APT) components are beneficial to patients who received distal femur limb-salvage surgery lacks high-quality clinical follow-up and mechanical evidence. This study aimed to investigate the biomechanics of the distal femur reconstructed with APT tumor knee prostheses using finite element (FE) analysis based on our previous, promising clinical outcome. METHODS: Three-dimensional FE models that use APT and metal-backed tibial (MBT) prostheses to reconstruct distal femoral bone defects were developed and input into the Abaqus FEA software version 6.10.1. Mesh refinement tests and gait simulation with a single foot both in the upright and 15°-flexion positions with mechanical loading were conducted. Stress distribution analysis was compared between APT and MBT at the two static positions. RESULTS: For both prosthesis types, the stress was concentrated on the junction of the stem and shaft, and the maximum stress in the femoral axis base was more than 100 Mpa. The stress on the tibial surface was relatively distributed, which was 1-19 MPa. The stress on the tibial bone-cement layer of the APT prosthesis was approximately 20 times higher than that on the MBT prosthesis in the same region. The stress on the proximal tibial cancellous bone and cortical bone of the APT prosthesis was 3-5 times greater than that of the MBT prosthesis, and it was more distributed. CONCLUSIONS: Although the stress of bone-cement around the APT component is relatively high, the stress was better distributed at the polyethylene-cement-bone interface in APT than in MBT prosthesis, which effectively protects the proximal tibia in distal femur tumor knee prosthesis replacement. These results should be considered when selecting the appropriate tibial component for a patient, especially under the foreseeable conditions of osteoporosis.

Effect of polylactic acid glue in preventing epidural scar adhesion after laminectomy in rabbits.

OBJECTIVE: To determine the efficacy of polylactic acid glue in preventing epidural scar adhesion after laminectomy in rabbits. METHODS: Twenty-four Japanese white rabbits underwent laminectomy (including the attached ligaments) at L(2 ) and L(5). After laminectomy at L(5), polylactic acid glue was sprayed on the dura and nerve roots and this segment was taken as the experimental group. After laminectomy at L(2), nothing was used and this segment was enrolled as the self control group. Four rabbits were killed every two weeks postoperatively till the end of the experiment at 12 weeks. Then the operated spine was observed grossly, histologically and ultrastructurally to check the degree of scar formation, the status of epidural scar adhesion, the absorption of the glue, and the intracellular structure of fibroblasts. RESULTS: The glue coagulated immediately after spraying and showed excellent hemostatic effect. The glue membrane was easy to be taken away from the dura mater of the samples for 2 weeks and there were no cells in the epidural space in the experimental group. But the dura mater was covered by hematoma in the control group, which formed mild adhesion, with fibroblasts proliferating actively. In the 4th week, some glue shivers remained in the epidural space with fibroblasts increasing a little, and the dura mater was smooth in the experimental group. However, in the control group, the formed scar was fragile and conglutinated with the dura mater diffusely and fibroblasts were much more than those in the experimental group. In the 6th-12th weeks, there was a potential interspace between the scar and the dura mater, and the polylactic acid glue was absorbed completely in the experimental group. Much tough scar was found in the control group, which was very difficult to dissect from the dura mater and the surrounding tissues. From the ultrastructural observation of the fibroblasts, the nucleus became much bigger and the rough endoplasmic reticulum was much more plentiful in the control group than that in the experimental group. CONCLUSIONS: Polylactic acid glue can effectively reduce epidural cicatrization and adhesion.

In vitro stress effect on degradation and drug release behaviors of basic fibroblast growth factor--poly(lactic-co-glycolic-acid) microsphere.

OBJECTIVE: To study the degradation and basic fibroblast growth factor (bFGF) release activity of bFGF - poly(lactic-co-glycolic-acid) microsphere (bFGF-PLGA MS) under stress in vitro, including the static pressure and shearing force-simulating mechanical environment of the joint cavity. METHOD: First, bFGF-PLGA MSs were created. Meanwhile, two self-made experimental instruments (static pressure and shearing force loading instruments) were initially explored to provide stress-simulating mechanical environment of the joint cavity. Then, bFGF-PLGA MSs were loaded into the two instruments respectively, to study microsphere degradation and drug release experiments. In the static pressure loading experiment, normal atmospheric pressure loading (approximately 0.1 MPa), 0.35 MPa, and 4.0 MPa pressure loading and shaking flask oscillation groups were designed to study bFGF-PLGA MS degradation and bFGF release. In the shearing force loading experiment, a pulsating pump was used to give the experimental group an output of 1,000 mL/min and the control group an output of 10 mL/min to carry out bFGF-PLGA MS degradation and drug release experiments. Changes of bFGF-PLGA MSs, including microsphere morphology, quality, weight-average molecular weight of polymer, and microsphere degradation and bFGF release, were analyzed respectively. RESULTS: In the static pressure loading experiment, bFGF-PLGA MSs at different pressure were stable initially. The trend of molecular weight change, quality loss, and bFGF release was consistent. Meanwhile, microsphere degradation and bFGF release rates in the 4.0 MPa pressure loading group were faster than those in the normal and 0.35 MPa pressure loading groups. It was the fastest in the shaking flask group, showing a statistically significant difference (P<0.0001). In the shearing force loading experiment, there were no distinctive differences in the rates of microsphere degradation and bFGF release between experimental and control group. Meanwhile, microsphere degradation and bFGF release rates by shaking flask oscillation were obviously faster than those by shearing force only (P<0.0001). CONCLUSION: There are significant effects on bFGF-PLGA MS degradation and bFGF release due to the interaction between extraction stress and time. Static pressure has a conspicuous influence on bFGF-PLGA MS degradation and release, especially at a pressure of 4.0 MPa. The shearing force has a slight effect on bFGF-PLGA MS degradation and drug release. On the contrary, shaking flask oscillation has a significantly distinctive effect.

[Effect of controlled release microspheres incorporating bFGF on Schwann cells].

OBJECTIVE: To investigate the effects of controlled release microspheres (Ms) incorporating bFGF on the cultured Schwann cells. METHODS: The secondary cultured Schwann cells were divided into three groups according to the different ingredients being added to the DMEM culture medium: bFGF group, and bFGF-PLGA-Ms group, and bFGF-PELA-Ms group. At different times after culture, the proliferative Schwann cells were collected from three groups individually. Then the number of Schwann cells was measured with cell counting method, the viability of Schwann cells was measured with MTT method and the cell cycle of Schwann cells was measured with flow cytometry. RESULTS: The in vitro cellular study showed that 1, 2 days after plate culture, the number of cells and the cell viability of bFGF group were significantly larger than those of bFGF-PLGA-Ms group and bFGF-PELA-Ms group. 3, 4 days after plate culture, the number of cells and the cell viability of bFGF group and bFGF-PLGA-Ms group were significantly larger than those of bFGF-PELA-Ms group. 6, 8 days after plate culture, the number of cells and the cell viability of bFGF-PLGA-Ms group was significantly larger than those of bFGF group and bFGF-PELA-Ms group. For the flow cytometry examination, 2 days after plate culture, the G2/ M+S percentage of bFGF group was the highest, and 4, 8 days after plate culture, the G2/M+S percentage of bFGF-PLGA-Ms group was the highest. CONCLUSION: Free bFGF can promote the proliferation of Schwann cells in a short period, while bFGF-PLGA-Ms can promote the proliferation of Schwann cells in a long period because of the controlled release of bFGF from microspheres. bFGF-PELA-Ms meets the property requirement of controlled release, but the biological activity of released bFGF is destroyed partially.

[Preparation of controlled release microsphere incorporating bFGF and its effect on Schwann cells].

To study the preparation method of bFGF microspheres and to investigate the bioactivities of bFGF, which were released from the bFGF microspheres, on the cultured schwann cells. bFGF was microcapsulated with the multiple emulsion encapsulative method using PLGA as coating material. Its morphology, particle size distribution, drug loading-embedding rate and in vitro release property were studied. The cultured schwann cells were grouped according to the different ingredients being added to the culture medium: bFGF group, bFGF-PLGA group. Then the number, the viability and the cell cycle of schwann cells were measured. The morphology and the particle size distribution of the bFGF-PLGA microspheres were even and good; the drug-loading and drug-embedding rate of microspheres were (27.18 x 10(-3)) % +/- (0.51 x 10(-3)) %, 66. 43% +/- 1.24%; the release property of microspheres in vitro was good and the overall release rate was 72. 47% in 11 days. The in vitro cellular study showed: 1, 2 days after plate culture, the cell number and cell viability of bFGF group was much better than that of bFGF-PLGA group; 3, 4 days after plate culture, the cell number and cell viability of bFGF group and bFGF-PLGA group were not different statistically; 6, 8 days after plate culture, the cell number and cell viability of bFGF-PLGA group was much better than that of bFGF group. Through the flow cytometry examination: 2 days after plate culture, the GJ/M+S percentage of bFGF group was higher than that of bFGF-PLGA group; 4, 8 days after plate culture, the G2/M+S percentage of bFGF-PLGA group was higher than that of bFGF group. So, it is practical to prepare the bFGF-PLGA microspheres with the multiple emulsion encapsulative method. bFGF-PLGA microspheres can preserve the bioactivities of bFGF effectively and promotes the proliferation of schwann cells in a long period because of the controlled release of bFGF from microspheres.

Reconstruction of Segmental Stability of Goat Cervical Spine with Poly (D, L-lactic acid) Cage.

OBJECTIVES: To compare the characteristics of inter body fusion after using an established poly (D, L-lactic acid) (PDLLA) cage, a titanium cage or autologous tricortical iliac crest graft in a goat cervical spine model in vivo. METHODS: Twenty-four goats were assigned to three groups: PDLLA cage group (n = 8), titanium alloy cage group (n = 8) and autologous iliac bone group (n = 8), and underwent C3-4 discectomy and fusion with the allocated procedure. Radiography was performed pre- and post-operatively and after 1, 2, 4, 8 and 12 weeks and disc space height (DSH), intervertebral angle (IVA), and lordosis angle (LA) measured at these time points. After 12 weeks, the goats were killed and fusion sites removed. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine the stiffness and range of motion (ROM). All specimens were also assessed histomorphologically. RESULTS: The IVA of PDLLA cage four weeks postoperatively and DSH eight and twelve weeks postoperatively were significantly greater than that of autologous iliac bone graft (P < 0.05). The LA values did not differ significantly between groups. The stiffness of both types of cages for axial rotation and lateral bending, and ROM for every movement, were significantly greater than that of the autologous iliac bone graft group (P < 0.05). PDLLA and titanium cages did not differ significantly (P > 0.05). Radiographic and histomorphological assessment showed better fusion in the cage than the autologous bone groups. CONCLUSION: The PDLLA cage can provide good intervertebral distract ability and enough biomechanical stability for cervical fusion.