Enhanced surface attachment of protein-type targeting ligands to poly(lactide-co-glycolide) nanoparticles using variable expression of polymeric acid functionality

The density of reactive carboxyl groups on the surface of poly(lactide-co-glycolide) (PLGA) nanoparticles (NP) was modulated using a combination of high-molecular weight (MW) encapped and low MW non-encapped PLGA. Carboxyl groups were activated using carbodiimide chemistry and conjugated to bovine serum albumin and a model polyclonal antibody. Activation of carboxyl groups in solution-phase PLGA prior to NP formation was compared with a postformation activation of peripheral carboxyl groups on intact NP. Activation before or after NP formation did not influence conjugation efficiency to NP prepared using 100% of the low-MW PLGA. The effect of steric stabilization using poly(vinyl alcohol) reduced conjugation of a polyclonal antibody from 62 microg/(mg NP) to 32 microg/(mg NP), but enhanced particulate stability. Increasing the amount of a high-MW PLGA also reduced conjugation, with the activation postformation still superior to the preformation approach. Drug release studies showed that high proportions of high-MW PLGA in the NP produced a longer sustained release profile of a model drug (celecoxib). It can be concluded that activating intact PLGA NP is superior to activating component parts prior to NP formation. Also, high MW PLGA could be used to prolong drug release, but at the expense of conjugation efficiency on to the NP surface.     

紫杉醇纳米粒子制备及血管内局部灌注后的组织分布

目的 制备紫杉醇纳米粒子,并考察其在实验兔体内经DispatchTM球囊灌注后组织分布情况.方法 以生物可降解材料聚乳酸聚乙醇酸共聚物(PLGA)为原料,采用超声乳化-溶剂挥发法制备载紫杉醇纳米粒子.对纳米粒子的粒径、形态、药物含量和体内外释放进行测定.通过新西兰兔腹主动脉局部给药模型考察紫杉醇纳米粒子球囊灌注后组织分布情况.结果 制备的紫杉醇纳米粒子的平均粒径约为246 nm,包封率为93.25％,紫杉醇含量19.06％.体外可维持恒定释放30d以上.新西兰兔体内经腹主动脉实现DispatchTM球囊灌注,观察药物可在靶部位体内贮留长达21d.结论 紫杉醇PLGA纳米粒子作为一种局部药物传递系统,经球囊灌注在动物模型体内提高局部药物浓度,延长药物作用时间,可实现缓释靶向治疗.     

Biodegradable and complexed microspheres used for sustained delivery and activity protection of SOD

To develop a new protein delivery system for superoxide dismutase (SOD), biodegradable materials like poly(DL-lactide-co-glycolide) (PLGA), alginate, and chitosan were used for preparing PLGA microspheres and alginate-chitosan microspheres, which were used for encapsulating protein. Alginate-chitosan microspheres showed much higher entrapment efficiency (91.08% +/- 1.28%) than that of PLGA microspheres (36.42% +/- 1.81%). In vitro release study showed that SOD presented a sustained release character in the preparation of these biodegradable materials. After 15 days, 43.72% +/- 0.43% of protein was released from alginate-chitosan microspheres, while there was 62.96% +/- 3.95% of protein release from PLGA microspheres. However, alginate-chitosan demonstrated that it was a better material to control the burst release of protein from microspheres. Furthermore, SOD activity in microspheres was evaluated, and the results showed that microspheres protected the activity of protein to some extent. Finally, PLGA-alginate-chitosan complex microspheres were constructed and the release character in vitro demonstrated that this preparation could not only prolong the release of drug but also decrease the burst release.     

The Effects of Lactidyl/Glycolidyl Ratio and Molecular Weight of Poly(D,L -Lactide-co-Glycolide) on the Tetracycline Entrapment and Release Kinetics of Drug-Loaded Nanofibers

Electrospun tetracycline (Tet)-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanofibers are considered to have great potential as local drug-delivery systems. This study was designed to explore the effects of the lactidyl/glycolidyl (LA/GA) unit ratio and molecular weight of PLGA on Tet entrapment efficiency and in vitro release kinetics. Three kinds of PLGA (PLGA75/25, M _w = 100 000 or 50 000; PLGA50/50, M _w = 50 000) were examined in this study. Electrospun nanofibers were fabricated containing 3, 5, 10 wt% Tet. The results showed that PLGA50/50 entrapped more Tet than both PLGA75/25 co-polymers, and the PLGA75/25 of M _w = 100 000 entrapped the least amount of Tet, suggesting that the lower the molecular weight of PLGA was, the higher the GA content in PLGA was and the higher the resulting Tet entrapment. Tet loading played an important role in Tet release. Nanofibers with 3 and 5 wt% Tet loading exhibited a sustained release for more than 28 days, whereas 10 wt% Tet only lasted 14 days. Loading of 3 wt% Tet resulted in approx. 35% release in the initial 12 h, 5 wt% Tet released approx. 70% and 10 wt% Tet resulted in approx. 85% release. The integrity of Tet incorporated into electrospun PLGA nanofibers was identified by FT-IR spectrum examination and the bacterial inhibition test. The modified Kirby–Bauer test showed dose-dependent inhibition of Staphylococcus aureus growth by Tet, confirming Tet structural stability throughout the electrospinning procedure. MG-63 cells demonstrated good adhesion and proliferation on all PLGA/Tet fibrous membranes. These results indicate that Tet entrapment and release kinetics of PLGA/Tet composite fibrous scaffolds can be tailored by the LA/GA ratios, molecular weights and drug loadings. Tet-loaded fibrous scaffolds show great potential for local drug delivery and bone defect repair.     

Antinociceptive effects of hydromorphone,bupivacaine and biphalin released from PLGA polymer after intrathecal implantation in rats

Intraspinal drug delivery, based on the concept of controlling pain by delivering drug to a nociceptive target rich in opioid and other relevant receptors is increasingly used clinically. The therapeutic ratio for opioids or other centrally acting agents is potentially greater if they are administered intrathecally (i.t.) than outside the central nervous system (CNS). The present study was designed with the ultimate goal of formulating a controlled release system for intrathecal analgesia characterized by effectiveness, rapid onset and few side effects for chronic pain control. A biodegradable copolymer poly(L-lactide-co-glycolide) (PLGA) was used to prepare a rod-shaped drug delivery system containing hydromorphone (HM), bupivacaine (BP), both HM and BP, or biphalin (BI). In vitro drug release kinetics of these systems showed a zero-order release rate for HM and BP from PLGA (85:15) rods. Drug-loaded rods were implanted i.t. Control groups received only placebo implants. Measurement of analgesic efficacy was carried out with tail flick and paw-withdrawal tests. In vivo studies showed potent, prolonged analgesia in comparison to controls for all active treatments. Analgesic synergy was observed with HM and BP. With further refinements of drug release rate, these rods may offer a clinically relevant alternative for intrathecal analgesia.     

In vitro and in vivo studies on vitamin E TPGS-emulsified poly(D,L-lactic-co-glycolic acid) nanoparticles for paclitaxel formulation

This work shows a full spectrum of research on Vitamin E TPGS-emulsified Poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) for paclitaxel formulation to improve its therapeutic index and to reduce the adverse effects of adjuvant Cremophor EL in its current clinical formulation of Taxol. Paclitaxel-loaded PLGA NPs were prepared by a modified solvent extraction/evaporation technique with vitamin E TPGS as emulsifier. The formulated NPs were found in quite uniform size of approximately 240 nm diameter. The in vitro drug release profile exhibited a biphasic pattern with an initial burst followed by a sustained release. In vitro HT-29 cell viability experiment demonstrated that the drug formulated in the NPs was 5.64, 5.36, 2.68, and 1.45 times more effective than that formulated in the Taxol formulation after 24, 48, 72, 96 h treatment, respectively at 0.25 microg/mL drug concentration, which should be even better with the sustainable release feature of the NPs formulation considered. In vivo PK measurement confirmed the advantages of the NP formulation versus Taxol. The area-under-the-curve (AUC) for 48 h for Vitamin E TPGS emulsified PLGA NP formulation of paclitaxel were found 3.0 times larger than that for the Taxol formulation. The sustainable therapeutic time, at which the drug concentration drops below the minimum effective value, for the NP formulation could be 1.67 times longer than that for the Taxol formulation.     

Multifunctional poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles decorated by Trastuzumab for targeted chemotherapy of breast cancer

This paper continued our earlier work on the poly(D,L-lactide-co-glycolide)/montmorillonite nanoparticles (PLGA/MMT NPs), which were further decorated by human epidermal growth factor receptor-2 (HER2) antibody Trastuzumab for targeted breast cancer chemotherapy with paclitaxel as a model anticancer drug. Such a NP system is multifunctional, which formulates anticancer drugs with no harmful adjuvant, reduces the side effects of the formulated anticancer drug, promotes synergistic therapeutic effects, and achieves targeted delivery of the therapy. The paclitaxel-loaded PLGA/MMT NPs were prepared by a modified solvent extraction/evaporation technique, which were then decorated with Trastuzumab. The effects of the surface decoration on particle size and size distribution, surface morphology, drug encapsulation efficiency, as well as the drug release kinetics, were investigated. The NP formulation exhibited a biphasic drug release with a moderate initial burst followed by a sustained release profile. The surface decoration speeded the drug release. Surface chemistry analysis was conducted by X-ray photoelectron spectroscopy (XPS), which confirmed the presence of Trastuzumab on the NP surface. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the stability of the antibody in the NP preparation process. Internalization of the coumarin-6-loaded PLGA/MMT NPs with or without the antibody decoration by both of Caco-2 colon adeno carcinoma cells and SK-BR-3 breast cancer cells was visualized by confocal laser scanning microscopy and quantitatively analyzed, which shows that the antibody decoration achieved significantly higher cellular uptake of the NPs. The results of in vitro cytotoxicity experiment on SK-BR-3 cells further proved the targeting effects of the antibody decoration. Judged by IC50 after 24h culture, the therapeutic effects of the drug formulated in the NPs with surface decoration could be 12.74 times higher than that of the bare NPs and 13.11 times higher than Taxol.     

Development of a sustained-release system for perivascular delivery of dipyridamole

Vascular access grafts implanted in dialysis patients are prone to failure in the long-term because of stenosis and occlusion caused by neointimal hyperplasia. Local delivery of antiproliferative drugs may be effective to prevent this consequence while minimizing the systemic side effects they cause. We developed a combination of poly(lactide-co-glycolide) (PLGA) microspheres with ReGel, an injectable copolymer, as a sustained-release system for perivascular delivery of an antiproliferative drug, dipyridamole. Dipyridamole-incorporated PLGA microspheres with various molecular weights (MWs) of PLGA were prepared by oil-in-water emulsion method. Encapsulation efficiency and surface morphology of microspheres were characterized. In vitro release kinetics of dipyridamole from ReGel or from microspheres/ReGel was experimentally determined. Without microspheres, 40% of the dipyridamole was released from ReGel as an initial burst in the first 3 days followed by continuous release in the subsequent 2 weeks. The use of PLGA microspheres decreased the initial burst and extended dipyridamole release from 23 to 35 days with increasing MW of PLGA. The highest MW PLGA showed a lag time of 17 days before consistent drug release occurred. Mixing microspheres and ReGel with two different MW PLGA achieved a continuous release for 35 days with little initial burst. In vivo release of dipyridamole from microspheres/ReGel exhibited a comparable release pattern to that seen in vitro. This injectable platform is a promising technique for sustained perivascular delivery of antiproliferative drugs.     

The administration of BDNF and GDNF to the brain via PLGA microparticles patterned within a degradable PEG-based hydrogel: Protein distribution and the glial response

Tailored delivery of neurotrophic factors (NFs) is a critical challenge that continues to inhibit strategies for guidance of axonal growth in vivo. Of particular importance is the ability to recreate innervation of distant brain regions by transplant tissue, for instance rebuilding the nigrostriatal track, one focus in Parkinson's disease research. Many strategies have utilized polymer drug delivery to target NF release in space and time, but combinatorial approaches are needed to deliver multiple NFs at relevant therapeutic times and locations without toxic side effects. Here we engineered a paradigm of PLGA microparticles entrapped within a degradable PEG-based hydrogel device to locally release two different types of NFs with two different release profiles. Hydrogel/microparticle devices were developed and analyzed for their ability to release GDNF in the caudal area of the brain, near the substantia nigra, or BDNF in the rostral area, near the striatum. The devices delivered their respective NFs in a region localized to within 100 μm of the bridge, but not exclusively to the targeted rostral or caudal ends. BDNF was slowly released over a 56-day period, whereas a bolus of GDNF was released around 28 days. The timed delivery of NFs from implanted devices significantly reduced the microglial response relative to sham surgeries. Given the coordinated drug delivery ability and reduced localized inflammatory response, this multifaceted PEG hydrogel/PLGA microparticle strategy may be a useful tool for further development in combining tissue engineering and drug delivery, and recreating the nigrostriatal track.     

Fabrication of multi-layered biodegradable drug delivery device based on micro-structuring of PLGA polymers

A programmable and biodegradable drug delivery device is desirable when a drug needs to be administered locally. While most local drug delivery devices made of biodegradable polymers relied on the degradation of the polymers, the degradation-based release control is often limited by the property of the polymers. Thus, we propose micro-geometry as an alternative measure of controlling drug release. The proposed devices consist of three functional layers: diffusion control layer via micro-orifices, diffusion layer, and drug reservoir layers. A micro-fabrication technology was used to shape an array of micro-orifices and micro-cavities in 85/15PLGA layers. A thin layer of fast degrading 50/50PLGA was placed as the diffusion layer between the 85/15PLGA layers to prevent any burst-type release. To modulate the release of the devices, the dimension and location of the micro-orifices were varied and the responding in vitro release response of tetracycline was monitored over 2 weeks. The release response to the different micro-geometry was prominent and further analyzed by FEM simulation. Comparison of the experiments to the simulated results identified that the variation of micro-geometry influenced also the volume-dependent degradation rate and induced the osmotic pressure.     

PLGA microsphere/calcium phosphate cement composites for tissue engineering: in vitro release and degradation characteristics

Bone cements with biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres have already been proven to provide a macroporous calcium phosphate cement (CPC) during in situ microsphere degradation. Furthermore, in vitro/in vivo release studies with these PLGA microsphere/CPC composites (PLGA/CPCs) showed a sustained release of osteo-inductive growth factor when drug was distributed inside/onto the microspheres. The goal of this study was to elucidate the mechanism behind drug release from PLGA/CPC. For this, in vitro release and degradation characteristics of a low-molecular-weight PLGA/CPC (M(w) = 5 kg/mol) were determined using bovine serum albumin (BSA) as a model protein. Two loading mechanisms were applied; BSA was either adsorbed onto the microspheres or incorporated inside the microspheres during double-emulsion. BSA release from PLGA microspheres and CPC was also measured and used as reference. Results show fast degrading polymer microspheres which produced a macroporous scaffold within 4 weeks, but also showed a concomitant release of acidic degradation products. BSA release from the PLGA/CPC was similar to the CPC samples and showed a pattern consisting of a small initial release, followed by a period of almost no sustained release. Separate PLGA microspheres exhibited a high burst release and release efficiency that was higher with the adsorbed samples. Combining degradation and release data we can conclude that for the PLGA/CPC samples BSA re-adsorbed to the cement surface after being released from the microspheres, which was mediated by the pH decrease during microsphere degradation.     

Controlled release of vascular endothelial growth factor using poly-lactic-co-glycolic acid microspheres: in vitro characterization and application in polycaprolactone fumarate nerve conduits

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulator. Controlled release of such stimulators may enhance and guide the vascularization process, and when applied in a nerve conduit may play a role in nerve regeneration. We report the fabrication and in vitro characterization of poly-lactic-co-glycolic acid (PLGA) microspheres encapsulating VEGF and the in vivo application of nerve conduits supplemented with VEGF-containing microspheres. PLGA microspheres containing VEGF were prepared by the double emulsion-solvent evaporation technique. This yielded 83.16% of microspheres with a diameter <53 μm. VEGF content measured by ELISA indicated 93.79±10.64% encapsulation efficiency. Release kinetics were characterized by an initial burst release of 67.6±8.25% within the first 24h, followed by consistent release of approximately 0.34% per day for 4 weeks. Bioactivity of the released VEGF was tested by human umbilical vein endothelial cell (HUVEC) proliferation assay. VEGF released at all time points enhanced HUVEC proliferation, confirming that VEGF retained its bioactivity throughout the 4 week time period. When the microsphere delivery system was placed in a biosynthetic nerve scaffold robust nerve regeneration was observed. This study established a novel system for controlled release of growth factors and enables in vivo studies of nerve conduits conditioned with this system.     

Controlled release of NFkappaB decoy oligonucleotides from biodegradable polymer microparticles

The objective of this study was to evaluate a poly(DL-lactic-co-glycolic acid)/poly(ethylene glycol) (PLGA/PEG) delivery system for nuclear factor-kappa B (NFkappaB) decoy phosphorothioated oligonucleotides (ODNs). PLGA/PEG microparticles loaded with ODNs were fabricated with entrapment efficiencies up to 70%. The effects of PEG contents (0, 5, and l0 wt%), ODN loading densities (0.4, 4, and 40 microg/mg), and pH of the incubation medium (pH 5, 7.4. and 10) on ODN release kinetics from the PLGA/PEG microparticles were investigated in vitro for up to 28 days. The release profiles in pH 7.4 phosphate buffered saline (PBS) were characterized by an initial burst during the first 2 days, a linear release phase until day 18, and a final release phase for the rest of the period. Up to 85% of the ODNs were released after 28 days in pH 7.4 PBS regardless of the ODN loading density and PEG content. Higher ODN loading densities resulted in lower entrapment efficiencies and greater initial burst effects. The bulk degradation of PLGA was not significantly affected by the PEG content and ODN loading density, but significantly accelerated at acidic buffer pH. Under acidic and basic conditions, the aggregation of microparticles resulted in significantly lower cumulative mass of released ODNs than that released at neutral pH. The effects of pH were reduced by the incorporation of PEG into PLGA microparticles. Since the PLGA degradation products are acidic, PLGA/PEG microparticles might provide a better ODN delivery vehicle than PLGA microparticles. These results suggest that PLGA/PEG microparticles are useful as delivery vehicles for controlled release of ODNs and merit further investigation in cell culture and animal models of glioblastoma.     

Preparation, characterization, and in vitro evaluation of physostigmine-loaded poly(ortho ester) and poly(ortho ester)/poly(D,L-lactide-co-glycolide) blend microspheres fabricated by spray drying

The physostigmine-loaded poly(ortho ester) (POE), poly(dl-lactide-co-glycolide) (PLGA) and POE/PLGA blend microspheres were fabricated by a spray drying technique. The in vitro degradation of, and physostigmine release from, the microspheres were investigated. SEM analysis showed that the POE and POE/PLGA blend particles were spherical. They were better dispersed when compared to the pure PLGA microspheres. Two glass transition temperature ( Tg ) values of the POE/PLGA blend microspheres were observed due to the phase separation of POE and PLGA in the blend system. XPS analysis proved that POE dominated the surfaces of POE/PLGA blend microspheres, indicating that the blend microspheres were coated with POE. The encapsulation efficiencies of all the microspheres were more than 95%. The incorporation of physostigmine reduced the Tg value of microspheres. The Tg value of the degrading microspheres increased with the release of physostigmine. For instance, POE blank microspheres and physostigmine-loaded POE microspheres had a Tg value of 67 degrees C and 48 degrees C, respectively. After 19 days in vitro incubation, Tg of the degrading POE microspheres increased to 55 degrees C. Weight loss studies showed that the degradation of the blend microspheres was accelerated with the presence of PLGA because its degradation products catalyzed the degradation of both POE and PLGA. The release rate of physostigmine increased with increase of PLGA content in the blend microspheres. The initial burst release of physostigmine was effectively suppressed by introducing POE to the blend microspheres. However, there was an optimized weight ratio of POE to PLGA (85:15 in weight), below which a high initial burst was induced. The POE/PLGA blend microspheres may make a good drug delivery system.     

Fabrication and characterization of controlled release poly(D,L-lactide-co-glycolide) millirods

A compression-heat molding procedure was developed to fabricate poly(D,L-lactide-co-glycolide) (PLGA) controlled release drug delivery devices for the local treatment of tumors. The drug delivery devices were designed in the shape of a cylindrical millirod (1.6-mm diameter, 10-mm length), which allows them to be implanted by a modified 14-gauge tissue biopsy needle into tumor tissues via image-guided interventional procedures. In this study, the prototype trypan blue-containing PLGA millirods were fabricated under a compression pressure of 4.6 x 10(6) Pa and different fabrication temperatures for 2 h. The scanning electron microscopy results showed complete polymer annealing for millirods fabricated at 80 and 90 degrees C, while the cross sections of the 60 and 70 degrees C millirods showed incompletely annealed PLGA microspheres and trypan blue powders. The density, flexural modulus, and release properties of the PLGA millirods were also characterized and compared. The average values of the density and flexural modulus of the millirods increased with an increase in fabrication temperature. The flexural modulus values of most PLGA millirods were above 1 x 10(8) Pa, which provides sufficient stiffness for implantation within the tumor tissue. In addition, a Delta c(p) method was developed to determine the loading density of trypan blue in the PLGA millirods by differential scanning calorimetry. Results from the Delta c(p) measurement showed that trypan blue was homogeneously distributed in the millirod. Release studies in phosphate-buffered saline showed that the release rate decreased for the millirods fabricated at higher temperatures. The times for the release of 50% trypan blue were 5, 25, 25, and 25 h for millirods fabricated at 60, 70, 80, and 90 degrees C, respectively. Millirods fabricated at 90 degrees C had the most reproducible release profiles. The results from this study established compression--heat molding as an effective method to fabricate controlled release PLGA millirods with sufficient mechanical strength and reproducible release profiles for local cancer therapy.     

Design and characterisation of new nanoparticulate polymer blends for drug delivery

The aim of the present work was the design of novel nanoparticle compositions based on poly(lactic acid/glycolic acid) (PLGA): poloxamer and PLGA: poloxamine blend matrices. For this purpose, we have applied a modified solvent diffusion technique that allows the preparation of the nanoparticles without the use of high energy sources. Nanoparticles have been prepared with different PLGA: poloxamer and PLGA: poloxamine ratios using PEO-derivatives with different molecular weights (Mw) and hydrophilia-lipophilia balance (HLB) values. Our results show that the physicochemical characteristics of the nanoparticles, such as size and zeta potential, are influenced by the type of PEO-derivative associated to the PLGA matrix. The 1H-NMR analysis of the different nanoparticle compositions showed that the extent of incorporation of the PEO-derivative depends strongly on its HLB and also on the nanoparticles preparation conditions. The capacity of these nanoparticles as drug delivery devices was evaluated using bovine insulin as a model drug. The insulin-encapsulation efficiency was shown to be dependent on the composition of the nanoparticles, those containing hydrophilic PEO-derivatives being the most effective in entrapping the drug molecules. The formation of the blend system displayed positive effects on the release characteristics of the nanoparticles. Nanoparticles exhibited a reduced initial burst and a nearly linear, constant release rate over a time period of two weeks.     

Fibrin promotes proliferation and matrix production of intervertebral disc cells cultured in three-dimensional poly(lactic-co-glycolic acid) scaffold

Previously, we have proven that fibrin and poly(lactic-co-glycolic acid) (PLGA) scaffolds facilitate cell proliferation, matrix production and early chondrogenesis of rabbit articular chondrocytes in in vitro and in vivo experiments. In this study, we evaluated the potential of fibrin/PLGA scaffold for intervertebral disc (IVD) tissue engineering using annulus fibrosus (AF) and nucleus pulposus (NP) cells in relation to potential clinical application. PLGA scaffolds were soaked in cells-fibrin suspension and polymerized by dropping thrombin-sodium chloride (CaCl(2)) solution. A PLGA-cell complex without fibrin was used as control. Higher cellular proliferation activity was observed in fibrin/PLGA-seeded AF and NP cells at each time point of 3, 7, 14 and 7 days using the MTT assay. After 3 weeks in vitro incubation, fibrin/PLGA exhibited a firmer gross morphology than PLGA groups. A significant cartilaginous tissue formation was observed in fibrin/PLGA, as proven by the development of cells cluster of various sizes and three-dimensional (3D) cartilaginous histoarchitecture and the presence of proteoglycan-rich matrix and glycosaminoglycan (GAG). The sGAG production measured by 1,9-dimethylmethylene blue (DMMB) assay revealed greater sGAG production in fibrin/PLGA than PLGA group. Immunohistochemical analyses showed expressions of collagen type II, aggrecan core protein and collagen type I genes throughout in vitro culture in both fibrin/PLGA and PLGA. In conclusion, fibrin promotes cell proliferation, stable in vitro tissue morphology, superior cartilaginous tissue formation and sGAG production of AF and NP cells cultured in PLGA scaffold. The 3D porous PLGA scaffold-cell complexes using fibrin can provide a vehicle for delivery of cells to regenerate tissue-engineered IVD tissue.     

异硫氰酸荧光素标记的神经生长因子缓释微球的制备及评价

目的 探讨异硫氰酸荧光素(FITC)标记的神经生长因子缓释微球的制备,并对其进行体内外评价.方法 采用水-油-水的双乳化技术制备FITC标记的神经生长因子缓释微球.利用扫描电镜和荧光显微镜对其形态特征进行观察,并对其体内外释放情况进行研究.结果 制备的FITC标记的神经生长因子缓释微球包封率和载药量分别为(97.9±8.9)%和(4.90±0.56)%.扫描电镜结果显示所制备的微球呈圆形、形态规整、粒径分布较均匀.荧光显微镜结果显示所包载的蛋白类药物在微球内旱随机分布.缓释微球体外持续释放5周后,有73%的蛋白释放出来;荧光示踪显示在体内能够持续释放达5周以上.结论 采用水-油-水的双乳化技术制备的缓释微球可以将生物大分子药物如神经生长因子成功运载到脑内.     

Chemically-modified polysaccharides for enzymatically-controlled oral drug delivery

Starch polysaccharides were investigated as bioerodible matrices for enzymatically-controlled oral drug delivery. Corn starch was ionically cross-linked with calcium chloride. It was found that the cross-linked starch could be used for entrapment and controlled release of bioactive molecules. The release rate of large molecules was degradation-dependent due to amylase activity, which might target the release to the intestine, when the particles were taken orally. The release of small molecules such as salicyclic acid, was mainly by diffusion.     

Incorporation of a sequential BMP-2/BMP-7 delivery system into chitosan-based scaffolds for bone tissue engineering

The aim of this study was to develop a 3-D construct carrying an inherent sequential growth factor delivery system. Poly(lactic acid-co-glycolic acid) (PLGA) nanocapsules loaded with bone morphogenetic protein BMP-2 and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocapsules loaded with BMP-7 made the early release of BMP-2 and longer term release of BMP-7 possible. 3-D fiber mesh scaffolds were prepared from chitosan and from chitosan–PEO by wet spinning. Chitosan of 4% concentration in 2% acetic acid (CHI4–HAc2) and chitosan (4%) and PEO (2%) in 5% acetic acid (CHI4–PEO2–HAc5) yielded scaffolds with smooth and rough fiber surfaces, respectively. These scaffolds were seeded with rat bone marrow mesenchymal stem cells (MSCs). When there were no nanoparticles the initial differentiation rate was higher on (CHI4–HAc2) scaffolds but by three weeks both the scaffolds had similar alkaline phosphatase (ALP) levels. The cell numbers were also comparable by the end of the third week. Incorporation of nanoparticles into the scaffolds was achieved by two different methods: incorporation within the scaffold fibers (NP–IN) and on the fibers (NP–ON). It was shown that incorporation on the CHI4–HAc2 fibers (NP–ON) prevented the burst release observed with the free nanoparticles, but this did not influence the total amount released in 25 days. However NP–IN for the same fibers revealed a much slower rate of release; ca. 70% released at the end of incubation period. The effect of single, simultaneous and sequential delivery of BMP-2 and BMP-7 from the CHI4–HAc2 scaffolds was studied in vitro using samples prepared with both incorporation methods. The effect of delivered agents was higher with the NP–ON samples. Delivery of BMP-2 alone suppressed cell proliferation while providing higher ALP activity compared to BMP-7. Simultaneous delivery was not particularly effective on cell numbers and ALP activity. The sequential delivery of BMP-2 and BMP-7, on the other hand, led to the highest ALP activity per cell (while suppressing proliferation) indicating the synergistic effect of using both growth factors holds promise for the production of tissue engineered bone.