NMR relaxation and diffusion studies to probe the motional dynamics of risperidone within PLGA microsphere

The present study aims to investigate the motional dynamics of risperidone within polylactic co-glycolic acid(PLGA)microsphere by employing solution state'H and 19F nuclear magnetic resonance(NMR)measurements.Risperidone,a second-generation fluorinated antipsychotic drug used for the treatment of schizophrenia is commercially marketed as PLGA microsphere formulation resulting in prolonged release of the drug in solution.Although the current trend in the pharmaceutical market is to develop drug formulation with long-acting release(LAR)products,complete physicochemical characterization of such formulations are scarce.Especially the effects of microsphere encapsulation on the motional properties and diffusion behavior of the drugs are not discussed adequately in any of the earlier reports.We therefore,have employed NMR relaxation and diffusion measurements to decipher the interaction of PLGA cavity water with risperidone.A detailed analysis of NMR relaxation rates confirmed the event of encapsulation and the presence of local motion in the non-fluorinated end of risperidone.Further,the relaxation data indicated a significant alteration in 19F chemical shift anisotropy(CSA)and CSA/dipole-dipole(DD)cross-correlated relaxation mechanism and decreased effect of solvent relaxation pointing out reduced water concentration within the microsphere cavity.'H and 19F diffusion coefficients of risperidone led to the information about hydrodynamic radius of risperidone in free and encapsulated states.Measurement of hydrodynamic radius supported the presence of limited water in PLGA cavity allowing higher translational mobility of risperidone after the encapsulation.

BCNU/PLGA microspheres:a promising strategy for the treatment of gliomas in mice

Objective：To investigate the effects of BCNU/PLGA microspheres on tumor growth,apoptosis and chemotherapy resistance in a C57BL/6 mice orthotopic brain glioma model using GL261 cell line.Methods：BCNU/PLGA sustained-release microspheres were prepared by the water-in-oil-in-water emulsion technique.GL261 cells were intracranially injected into C57BL/6 mouse by using the stereotactic technology.A total of 60 tumor-bearing mice were randomly and equally divided into three groups：untreated control,PLGA treated,BCNU/PLGA treated.Magnetic resonance imaging （MRI） was taken to evaluate tumor volume.BCNU/PLGA sustained-release wafers were implanted in the treatment group two weeks after inoculation.Survival time and quality were observed.Specimens were harvested,and immunohistochemical staining was used to check the expression of Bax,Bcl-2,and O6-methylguanine-DNA methyltransferase （MGMT）.Statistical methods was used for analysis of relevant data.Results：BCNU/PLGA sustained-release wafers were fabricated and implanted successfully.There is statistical difference of survival time between the BCNU/PLGA treated group and control groups （P＜0.05）.MRIscan showed inhibitory effect of BCNU/PLGA on tumor growth.Compared to the group A and B,BCNU/PLGA decreased the expression of apoptosis related gene Bcl-2 （P＜0.05）,but did not elevate the expression level of Bax （P＞0.05）,with the ratio of Bax/Bcl-2 increased.For MGMT protein expression,no statistically significant change was found in treated group （P＞0.05）.Conclusions：Local implantation of BCNU/PLGA microspheres improved the survival quality and time of GL261 glioma-bearing mice significandy,inhibited the tumor proliferation,induced more cell apoptosis,and did not increase the chemotherapy resistance.

Preparation and Characterization of Lung-targeting Cefquinome-loaded PLGA Microspheres

We developed poly lactic-co-glycolic acid（PLGA） microspheres loaded with cefquinome and tested their effectiveness in a mouse model. The microspheres were prepared by optimizing several key parameters such as PLGA molecular weight, drug/polymer ratio, internal water volume and ethyl acetate. Drug loading efficiency, stability, in vitro release and tissue distribution in mouse were evaluated. The average particle size of the microspheres was 27.84 μm. The drug loading efficiency was 64.57%. The in vitro release of cefquinome from microspheres after 4 h was about 40% compared with over 90% for the drug alone. The concentration of cefquinome in lung reached 25 μg/g 0.25 h after injection, and kept at 10 μg/g 4 h after injection. However, the concentration of cefquinome was very low in other organs even 0.25 h after injection. In conclusion, Cefquinome-loaded PLGA microspheres are compatible as an effective lung-targeting drug delivery system and have a good sustained release efficacy.

Effect of Excipients on Stability and Structure of rhCuZn-SOD Encapsulated in PLGA Microspheres

When a protein is encapsulated into poly( DL -lactide-co-glycolide)(PLGA) microspheres by means of the double-emulsion method,the harsh microspheres formation process including ultrasonification,exposure to an organic solvent and a polymer may cause the denaturation of the protein. In this study,we investigated the enzymatic activity change and the effect of the excipients on the stability of recombinant human Cu,Zn-superoxide dismutase(rhCu,Zn-SOD) during the emulsification. The specific activity recovery was found to be concentration dependent and the excipients involved such as PEG 600 and Tween 20,and trehalose were shown to increase the stability of rhCu,Zn-SOD. The protein structural integrity within the microspheres was analyzed by FTIR. The structure of rhCu,Zn-SOD within PLGA microspheres containing trehalose was found to be similar to that of the native solid state,whereas the protein encapsulated during the preparation in the absence of any excipient changed due to the possible hydrophobic interaction with the polymer. The results suggest that a rational stability strategy for protein to be encapsulated into microspheres should aim at different processes.

Drug-nanoencapsulated PLGA microspheres prepared by emulsion electrospray with controlled release behavior

The development of modern therapeutics has raised the requirement for controlled drug delivery system which is able to efficiently encapsulate bioactive agents and achieve their release at a desired rate satisfying the need of the practical system.In this study,two kind of aqueous model drugs with different molecule weight,Congo red and albumin from bovine serum(BSA)were nanoencapsulated in poly(DL-lactic-co-glycolic acid)(PLGA)microspheres by emulsion electrospray.In the preparation process,the aqueous phase of drugs was added into the PLGA chloroform solution to form the emulsion solution.The emulsion was then electrosprayed to fabricate drugnanoencapsulated PLGA microspheres.The morphology of the PLGA microspheres was affected by the volume ratio of aqueous drug phase and organic PLGA phase(V_(w)/V_(o))and the molecule weight of model drugs.Confocal laser scanning microcopy showed the nanodroplets of drug phase were scattered in the PLGA microspheres homogenously with different distribution patterns related to V_(w)/V_(o).With the increase of the volume ratio of aqueous drug phase,the number of nanodroplets increased forming continuous phase gradually that could accelerate drug release rate.Moreover,BSA showed a slower release rate from PLGA microspheres comparing to Congo red,which indicated the drug release rate could be affected by not only V_(w)/V_(o)but also the molecule weight of model drug.In brief,the PLGA microspheres prepared using emulsion electrospray provided an efficient and simple systemto achieve controlled drug release at a desired rate satisfying the need of the practices.

Novel PLGA Microspheres for Sustained Delivery of Antisense Oligonucleotide

Novel poly（lactide-co-glycolide acid）（PLGA） microspheres were developed for sustained delivery of antisense oligonucleotide（ASO）. First, a new cationic agent, polyethylenimine（PEI） conjugated to linoleic acid（LA）（PEI-LA） was synthesized by reacting PEI（Mw=800） with linoleoyl chloride. Then, PEI-LA was combined with LOR-2501 to form electrostatic complexes at moderate nitrogen-to-phosphate（N/P） molar ratios which were then encapsulated into poly（lactide-co-glycolide） microspheres by a multiple emulsion-solvent evaporation technique. With an increase in ASO/PEI-LA concentration from 5% to 10%, encapsulation efficiency of ASO in the micro- spheres reduced from 72.14% to 57.62%, and the particle size ofmicrospheres increased from 28.58 μm to 34.76 μm. In vitro studies show that the release profile of ASO from microspheres prepared at 7.5% ASO-PEI-LA lasted for 14 d The novel microspheres have a potential use as a sustained release vehicle for ASO.

Fabrication of hollow porous PLGA microspheres for controlled protein release and promotion of cell compatibility

This letter reports on the fabrication of hollow,porous and non-porous poly（D,L-lactide-co-glycolide） （PLGA） microspheres（MSs） for the controlled release of protein and promotion of cell compatibility of tough hydrogels.PLGA MSs with different structures were prepared with modified double emulsion methods,using bovine serum albumin（BSA） as a porogen during emulsification.The release of the residual BSA from PLGA MSs was investigated as a function of the MS structure.The hollow PLGA MSs show a faster protein release than the porous MSs,while the non-porous MSs have the slowest protein release.Compositing the PLGA MSs with poly（vinyl alcohol）（PVA） hydrogels promoted chondrocyte adhesion and proliferation on the hydrogels.

Preparation of PLGA Microspheres with Different Porous Morphologies

Poly（D,L-lactide-co-glycolide）（PLGA） microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell（denoted by hollow in brief） and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin（BSA） was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.

Preparation of PLGA Ceftiofur Hydrochlorate Lung- targeted Microsphere with Spray Drying Process

To explore the preparation of PLGA ceftiofur hydrochlorate lung-targeted microsphere with spray drying process, the preparation technics was optimized by orthogonal experiments. Appearance, particle size, drug-loaded properties and medicine dissolution rate of the microsphere were evaluated. The experimental results show that the prepared PLGA microspheres loaded with ceftiofur hydrochlorate have good appearance, good encapsulate rate and dissolution. The drug loading capacity of ceftiofur-hydrochlorate-loaded PLGA microsphere prepared with spray drying process is 23.06%, i e, when the dosing ratio is 1：3, the encapsulate rate is 92.23% at maximum, and the release percentage of medicine is at 0.5 h. The medicine is released almost completely at 20 h and the accumulated medicine release is 98.12%.

An accelerated method to evaluate thymopentin release from microspheres in vitro

To design an accelerated method to evaluate thymopentin release from PLGA microspheres in vitro. Microspheres were prepared by double emulsion technique, using poly（lactide-co-glycolide） （PLGA） as carrier. At higher medium temperature （45℃, 50℃ and 55℃）, an accelerated release testing in short time was studied and correlated with the conventional release （37℃） in vitro. The release in vitro of thymopentin from PLGA microspheres at 45 ℃, 50℃ and 55℃ was significantly accelerated （P 〈 0.05）. In particular, at 50℃, an accelerated release （30 h） of the hydrophilic peptide from the PLGA matrix was achieved and correlated well with the conventional release （30 d）. An accelerated release testing in vitro at higher temperature could be used to monitor thymopentin release from PLGA microspheres.

Fabrication, bacteriostasis and osteointegration properties researches of the additively-manufactured porous tantalum scaffolds loading vancomycin

Infected bone defects(IBDs)remains a challenging problem for orthopedists.Clinically,routine management for IBDs has two stages:debridement and systematic antibiotics administration to control infection,and secondary grafting to repair bone defects.Whereas the efficacy is not satisfactory,because the overuse of antibiotics may lead to systemic toxicity,and the emergence of drug-resistant bacteria,as well as the secondary surgery would cause additional trauma and economic burden to the patients.Therefore,it is imperative to develop a novel scaffold for one-stage repair of IBDs.In this study,vancomycin(Van)was encapsulated into poly(lactic co-glycolic acid)(PLGA)microspheres through the double emulsion method,which were then loaded into the additively-manufactured porous tantalum(AM-Ta)through gelatin methacryloyl(GelMA)hydrogel to produce the composite Ta/GelMA hydrogel(Gel)/PLGA/vancomycin(Van)scaffolds for repairing IBDs.Physiochemical characterization of the newly-developed scaffold indicated that the releasing duration of Van was over 2 weeks.Biological experiments indicated good biocompatibility of the composite scaffold,as well as bacteriostasis and osteointegration properties,which showed great potential for clinical application.The construction of this novel scaffold would provide new sight into the development of orthopaedic implants,shedding a novel light on the treatment of IBDs.

Development of an antimicrobial peptide-loaded mineralized collagen bone scaffold for infective bone defect repair

The repair of infective bone defects is a great challenge in clinical work.It is of vital importance to develop a kind of bone scaffold with good osteogenic properties and long-term antibacterial activity for local anti-infection and bone regeneration.A porous mineralized collagen(MC)scaffold containing poly(D,L-lactide-co-glycolic acid)(PLGA)microspheres loaded with two antibacterial synthetic peptides,Pac-525 or KSL-W was developed and characterized via scanning electron microscopy(SEM),porosity measurement,swelling and mechanical tests.The results showed that the MC scaffold embedded with smooth and compact PLGA microspheres had a positive effect on cell growth and also had antibacterial properties.Through toxicity analysis,cell morphology and proliferation analysis and alkaline phosphatase evaluation,the antibacterial scaffolds showed excellent biocompatibility and osteogenic activity.The antibacterial property evaluated with Staphylococcus aureus and Escherichia coli suggested that the sustained release of Pac-525 or KSL-W from the scaffolds could inhibit the bacterial growth aforementioned in the long term.Our results suggest that the antimicrobial peptides-loaded MC bone scaffold has good antibacterial and osteogenic activities,thus providing a great promise for the treatment of infective bone defects.