Injectable nanospheres from a novel multiblock copolymer: Cytocompatibility,degradation and in vitro release studies

The aim was to develop and characterize nanospheres made from a newly synthesized poly (D, L-lactide-co-ethyleneglycol) (-PLA-PEG-PLA-)_n multi-block copolymer. Nanospheres were prepared under optimized conditions of modified emulsion-solvent evaporation technique in a continuous flow process using rhodamine B as a drug model. They were characterized for size distribution, zeta (ζ) potential, porosity and morphology. Drug loading and yield were also determined. In vitro degradation studies of the copolymer were conducted in phosphate buffer (pH 7.4) at 37°C. The cytotoxic properties of the polymer and vector were analysed by dimethylthiazoldiphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays on the B16 mouse cell line. Release of rhodamine B from the nanospheres was assayed in vitro using a dialysis bag in isotonic phosphate buffer (pH 7.4) at 37°C. Spherical and non-porous nanospheres with mean size less than 800nm could be prepared. The (ζ) potential was neutral. The average yield was approximately 70% with 7% rhodamine loading. A total of 50% of the multiblock underwent initial degradation after 4 weeks, while degradation was complete after 16 weeks. Cellular proliferation was not inhibited as no cytotoxicity was observed with the copolymers and nanospheres. Rhodamine B was released in a stepwise pattern. The initial burst was 20%, and release was prolonged thereafter for 29 days. Thus, injectable nanospheres with prolonged rhodamine B release have been designed and characterized as a potential drug-delivery system.     

Injectable block copolymer hydrogels for sustained release of a PEGylated drug

The paper employs the spontaneous physical gelling property of a biodegradable polymer in water to prepare an injectable sustained release carrier for a PEGylated drug. A series of thermogelling PLGA-PEG-PLGA triblock copolymers were synthesized. The PEGylated camptothecin (CPT) was also prepared and employed as the model of a PEGylated drug, and the solubility of this hydrophobic drug was significantly enhanced to over 150mg/mL. The model drug was completely entrapped into the polymeric hydrogel, and the sustained release lasted for 1 month. The mechanism of the sustained release was diffusion-controlled at the first stage and then was the combination of diffusion and degradation at the late stage. In vivo anti-tumor tests in mice further confirmed the efficacy of the model PEGylated drug released from the hydrogel. This work also revealed the specificity of the PEGylated drug in such a kind of carrier systems by decreasing the critical gelling temperature and increasing the viscosity of the sol. Due to the very convenient drug formulation and highly tunable release rate, an injectable carrier platform for PEGylated drugs is thus set up.     

PVP magnetic nanospheres: biocompatibility, in vitro and in vivo bleomycin release

PURPOSE: To synthesize and characterize a magnetic micromolecular delivery system based on PVP hydrogel with polyvinyl alcohol (PVA) as the crosslinker. METHODS: The microparticles were successfully prepared using 25 kGy Co-60 gamma-ray irradiation and characterized. Biocompatibility, in vitro and in vivo drug release tests were carried out. RESULTS AND DISCUSSION: Bleomycin was quantitatively released with in slightly over 8 h (hours) from the nanospheres containing 1mg bleomycin while the time was longer for those containing 5 mg. On the other hand free bleomycin quantitatively passed through the dialysis baffle with in only 3.5 h. For both 5 and 1 mg of bound bleomycin, it took up to 2 h to reach peak concentration compared to 30 min for the free drug. CONCLUSION: The PVP hydrogel magnetic nanospheres exhibited passive drug release that could be exploited to enhance therapeutic efficacy. The present results indicate that PVP hydrogel based magnetic nanospheres have potential as drug carriers in magnetic guided chemotherapeutic drug delivery.     

他克莫司纳米微球的制备及其体外释药性能

目的采用甲氧基聚乙二醇-聚乳酸聚合物（PEG—PLA）制备他克莫司微球（PPT），研究其体外释药特性。方法考察PPT的载药量、包封率、粒径大小、粒径分布和药物体外释放实验。结果PPT的制备工艺稳定、重复性好，微球外形圆整，表面光滑，分布均匀，平均粒径为（545．1±0．9）nm，平均载药量为（18．90±3．22）％，平均包封率为（25．0±1．6）％，35d的药物累积释放率为67．21％。结论他克莫司微球缓释时间长达35d，能够满足临床治疗的要求。     

Preparation, characterization and in vitro drug release studies of novel polymeric nanoparticles

Polymeric nanoparticles of AADG cross-linked with MBA encapsulating water soluble macromolecules such as FITC-Dextran have been prepared in the reverse micellar system. The particles obtained were of >85nm in diameter which were highly monodisperse. An optically clear solution was obtained on redispersing these nanoparticles in aqueous buffer. Size and morphology of the particles remains the same on re-dispersing the lyophilized powder of these nanoparticles in aqueous buffer. The size dependency of the particles on the monomer and surfactant concentration was observed. The average size of the nanoparticles as obtained from DLS studies ranges from 74 to 114nm in case 0.06M AOT and 62-104nm in case of 0.1M AOT concentration. FITC-Dextran was entrapped into nanoparticles with high efficiency (>70%). The pH dependent release of the entrapped molecules from these nanoparticles was also studied. At pH 5.0 solution, approximately 43% of FITC-Dx was released and at pH 7.4 it was about 70%.     

Prednisolone-loaded albumin nanospheres: in vitro and in vivo evaluation studies

Prednisolone-loaded bovine serum albumin (BSA) nanospheres prepared by pH-coacervation were evaluated regarding recovery, drug entrapment efficiency, particle size, shape, surface morphology, in vitro drug release profile, and in vivo distribution. The method of analysis was validated in terms of accuracy, precision, and repeatability. No significant change in the drug's chemical integrity was observed when incorporated in the nanospheres. It was observed that the average particle size and drug entrapment efficiency of the nanospheres increased with the increase in drug loading. All the batches exhibited biphasic drug release with an initial burst effect followed by gradual steady release. The higher the drug loading, the greater was the burst effect. The mechanism of prednisolone release from the nanospheres was found to be due to diffusion and erosion as observed by fitting the release data in different models. The drug's in vivo distribution was found to be highest in the liver followed by the spleen and lungs. Stability studies indicated that nanosphere formulations should be stored at 4 +/- 2 degrees C.     

In vitro studies on release and skin permeation of nonivamide from novel oil-in-oil-emulsions

The purpose of this study was to develop oil-in-oil-emulsions that facilitate long-term treatment for chronic pruritus with capsaicinoids. To this end, oil-in-oil-emulsions, which comprised polydimethyl siloxanes, silicone surfactant and castor oil, were examined. We used nonivamide, a synthetic analogue of capsaicin as the active pharmaceutical ingredient. It was incorporated into castor oil that formed the dispersed phase of the emulsion. We evaluated the influence of formulation variables (nonivamide content, phase volume ratio and viscosity of the silicone oil) on the in vitro release and the permeation of nonivamide. Permeation was found to be controlled by the nonivamide concentration in the dispersed phase and the phase volume ratio. Oil-in-oil-emulsions were found to produce constant permeation rates over a period of 10 h. They are thus superior to conventional semisolid formulations as application intervals may be extended.     

Release of small water-soluble drugs from multiblock copolymer microspheres: a feasibility study.

Poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) multiblock copolymer was investigated as a possible matrix for controlled delivery of small water-soluble drugs. Two molecules were selected as sustained release candidates from microspheres: leuprorelin acetate (peptide of Mw = 1270 D) and vitamin B(12) (Mw = 1355 D). First, vitamin B(12)-loaded microspheres were prepared using a double emulsion method and preparation parameters were varied (surfactant in the first emulsion and copolymer composition). The resulting microsphere structure, entrapment efficiency and release rate were evaluated. Vitamin B(12)-loaded microsphere parameters could easily be tailored to achieve specific requirements. The addition of surfactant in the first preparation process led to a significant increase of the microsphere entrapment efficiency, whereas the decrease of the PEGT copolymer content allowed the release rates from microspheres to be precisely decreased. However, leuprorelin acetate-loaded microspheres did not show the same characteristics when prepared with the same parameters, possibly because of a high water solubility discrepancy between the vitamin B(12) and the peptide. This study shows the suitability of PEGT/PBT microspheres as a controlled release system for vitamin B(12), but not for leuprorelin acetate. It also underlines the necessity of tailored development for each individual drug and emphasizes the risk of using model molecules.     

Injectable biodegradable temperature-responsive PLGA-PEG-PLGA copolymers: synthesis and effect of copolymer composition on the drug release from the copolymer-based hydrogels

Injectable biodegradable temperature-responsive poly(DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers with DL-lactide/glycolide molar ratio ranging from 6/1 to 15/l were synthesized from monomers of DL-lactide, glycolide and polyethylene glycol and characterized by 1H NMR. The resulting copolymers are soluble in water to form free flowing fluid at room temperature but become hydrogels at body temperature. The hydrophobicity of the copolymer increased with the increasing of DL-lactide/glycolide molar ratio. In vitro dissolution studies with two different hydrophobic drugs (5-fluorouracil and indomethacin) were performed to study the effect of DL-lactide/glycolide molar ratio on drug release and to elucidate drug release mechanism. The release mechanism for hydrophilic 5-fluorouracil was diffusion-controlled, while hydrophobic indomethacin showed an biphasic profile comprising of an initial diffusion-controlled stage followed by the hydrogel erosion-dominated stage. The effect of DL-lactide/glycolide molar ratio on drug release seemed to be dependent on the drug release mechanism. It has less effect on the drug release during the diffusion-controlled stage, but significantly affected drug release during the hydrogel erosion-controlled stage. Compared with ReGel system, the synthesized copolymers showed a higher gelation temperature and longer period of drug release. The copolymers can solubilize the hydrophobic indomethacin and the solubility (13.7 mg/ml) was increased 3425-fold compared to that in water (4 microg/ml, 25 degrees C). Two methods of physical mixing method and solvent evaporation method were used for drug solubilization and the latter method showed higher solubilization efficiency.     

Reversible aggregation of lysozyme in a biodegradable amphiphilic multiblock copolymer.

Lysozyme-loaded poly(ethylene glycol terephthalate)-poly(butylene terephthalate) (PEGT/PBT) films were prepared using a water-in-oil emulsification solvent evaporation method. Infrared spectroscopic analysis of the dried films indicated the presence of non-covalent lysozyme aggregates in the polymer matrix. The use of methanol to enhance the drying rate of the films increased the relative amount of aggregates. Surprisingly, quantitative in-vitro release of fully active, non-aggregated lysozyme was observed, indicating that lysozyme forms reversible aggregates during encapsulation in PEGT/PBT films.     

三氧化二砷白蛋白纳米微球的制备及体外释药特性

目的:制备三氧化二砷白蛋白纳米微球(As_2O_3-BSA-NS)并鉴定其体外释放特性。方法:通过交联固化的方法制备三氧化二砷蛋白徽球。以粒子(粒径<1μm)分布百分数、载药量和包封率为指标设立总的优化指数(DF)。选择因素有油相/水相比、高速分散速度、BSA浓度和搅拌固化时间,按正交设计优化制备工艺。用体外释药方法研究其释放特性。结果:4个因素中,高速分散速度对总优化指数影响最大(P<0.01),其次是BSA浓度和油相/水相比(P<0.05),搅拌固化时间对指数几乎没有影响(P>0.05)。体外释药实验证实三氧化二砷蛋白微球释药速度明显慢于单纯的三氧化二砷。结论:使用优化的交联固化的方法可以制备出符合要求的三氧化二砷蛋白微球,其具有明显的缓释功能。     

Shrinkage of a rapidly growing tumor by drug-loaded polymersomes: pH-triggered release through copolymer degradation

Carrier-mediated delivery of drugs into the cytosol is often limited by either release from the carrier or release from an internalizing endolysosome. Here, loading, delivery, and cytosolic uptake of drug mixtures from degradable polymersomes are shown to exploit both the thick membrane of these block copolymer vesicles and their aqueous lumen as well as pH-triggered release within endolysosomes. Our initial in vivo studies demonstrate growth arrest and shrinkage of rapidly growing tumors after a single intravenous injection of polymersomes composed of poly(ethylene glycol)-polyester. Vesicles are shown to break down into membrane-lytic micelles within hours at 37 degrees C and low pH, although storage at 4 degrees C allows retention of drug for over a month. It is then shown that cell entry of the polymersomes into endolysosomes is followed by copolymer-induced endolysosomal rupture with release of cytotoxic drugs. Above a critical poration concentration (CCPC) that is easily achieved within endolysosomes and that scales with copolymer proportions and molecular weight, the copolymer micelles are seen to disrupt lipid membranes and thereby enhance drug activity. Neutral polymersomes and related macrosurfactant assemblies can thus create novel pathways within cells for controlled release and delivery.     

Caffeine-loaded niosomes: characterization and in vitro release studies

We prepared different neutral and positively charged niosomal formulations containing sorbitan esters for entrapment of caffeine. Drug entrapment reduced following the incorporation of positively charged molecule. Furthermore, the span 60-containing niosomes showed the highest drug encapsulation efficiency due to solid-state nature of this surfactant's bilayers. There was a regular relationship between lipophilicity (HLB values) of surfactants and mean particle sizes; increasing the HLB value resulted in larger niosomes. By means of diffusion experiments with Franz diffusion cells, the effects of different vesicular components and that of the positive charge on the release of caffeine from various vesicle formulations were studied. Obtained results indicate that a combined erosion-diffusion mechanism regulates the permeation of caffeine through cellulose acetate membranes. High encapsulation efficiency, appropriate size distribution, and good vesicular stability, especially in solid state niosomes, make this type of vesicular systems a good alternative to liposomes for topical delivery of caffeine.     

Controlled release of growth hormone from thermosensitive triblock copolymer systems: In vitro and in vivo evaluation

The purpose of this study was to design injectable controlled release polymer formulations for growth hormone using triblock copolymer PLGA-PEG-PLGA (MW 1400-1000-1400). Porcine growth hormone (pGH) formulations were prepared by adding pGH into 30% (w/v) aqueous solution of triblock copolymer. pGH concentrations in the released samples were determined using a standard MicroBCA method. In vitro release studies demonstrated that there were no initial burst of pGH from both formulations containing a low dose (0.12%, w/v) and a high dose (0.42%, w/v) of pGH. In vivo absorption study of pGH in rabbits showed that constant serum levels of exogenous pGH (3-7 ng/mL from high dose and 2-4 ng/mL from low dose) were detected for nearly 4 weeks from delivery systems upon single subcutaneous injection. The absolute bioavailability of pGH enhanced from the thermosensitive polymer-based systems, which was approximately 5-15-fold those of subcutaneous aqueous solution. MTT assay and light microscopy were used to investigate the in vitro and in vivo biocompatibility of thermosensitive polymer delivery systems, respectively. Both in vitro and in vivo results support the biocompatible nature of these polymer delivery systems. Thus, the triblock copolymer used in this study was able to control the release of incorporated pGH in vitro and in vivo for longer duration and the delivery system was biocompatible.     

Bromhexine: in vitro and in vivo studies of release from mono- and bi-component preparations

The in vitro dissolution characteristics of bromhexine and its hydrochloride salt have been investigated in the presence and absence of a cephalosporin antibiotic, Bioavailability of the salt and of the antibiotic from combination capsules have also been studied. In conditions typical of dissolution tests for formulated products, no significant differences were observed in the in vitro dissolution rates of the base and its salt in mono-component preparations. Some slowing of solution rate of the base was observed in bi-component preparations. In vivo, peak plasma levels of bromhexine hydrochloride and cefaclor were $\text{18.1 ± 2.3}\text{ng}\text{”}\text{ml}{}^{\mathrm{?1}}$ and $\text{15.3 ± 0.9 μ}\text{g}\text{”}\text{ml}$^?1, respectively, from the combination formulation and were similar to levels found with the mono-component preparations.     

Heparin release from hydrophobic polymers: (I)In vitro studies

The release of heparin from monolithic devices composed of different ratios of polyethylene oxide (PEO MW 20, 000) and hydrophobic polydimethylsiloxane or polyurethane was investigated. Water soluble PEO blended into the polymers provided a controlled release of heparin. The release rate of heparin could be controlled by varying the content of PEO. The heparin release rate from the devices increased as the content of PEO in the devices increased. The release mechanism may be associated with the creation of pore or domain through the devices following the swelling and the change in the physical structure of the polymer network. Hydrophobic polydimethylsiloxanes and polyurethanes containing PEO can provide and antithrombogenic material for prolonged release of heparin from a heparin blended system.     

Association of cyclosporin to isohexylcyanoacrylate nanospheres and subsequent release in human plasma in vitro.

Polyisohexylcyanoacrylate nanocapsules containing cyclosporin were prepared by mixing in a 1:2 ratio an oil/ethanol solution of monomer and drug with an aqueous phase. Drug nanoencapsulation rate was controlled by its partition coefficient between the inner (organic) and outer (aqueous) phases. Thus highest encapsulation yields (88 per cent) were achieved by reducing cyclosporin solubility in the aqueous phase, i.e. by reducing ethanol concentration under reduced pressure, achieving a 3-fold volume reduction. Due to the relative insolubility of cyclosporin in water, no drug was released from the nanocapsules during storage in this injectable vehicle. Upon a 1/5 dilution in human plasma at 37 degrees C in vitro around 40 per cent of the initially encapsulated cyclosporin diffused quickly out of the capsules and an equilibrium was reached, the drug being most likely dissolved in the fatty compartment of the plasma such as lipoproteins, etc. This release mechanism is different from plain polymeric nanoparticles. Indeed, in this case the drug was released in two phases: an initial burst (around 60 per cent) of adsorbed drug as a result of the dilution, followed by a slow release (around 20 per cent over 3 h) which is likely to result from the progressive enzymatic erosion of the polymer. The initial burst was markedly more pronounced (around 80 per cent) when nanoparticle suspensions were evaporated to 1/3 of their initial volume under reduced pressure. Finally, experiments performed at 0 degree C allowed a reduction of the fraction released immediately from both types of nanospheres, probably because of a reduced solubility in plasma. In the case of nanoparticles the second phase of slow release is also inhibited at 0 degree C, in agreement with an enzymatically controlled release mechanism.     

Design,in vitro release characterization and pharmacokinetics of novel controlled release pellets containing levodropropizine

Abstract

This study was performed to investigate the in vitro release characteristics of levodropropizine (LDP) from novel dual-coated sustained release (SR) pellets, and evaluate the pharmacokinetics of a novel controlled release (CR) preparation composed of the dual-coated SR pellets and immediate release (IR) LDP pellets. The dual-coated SR pellets composed of a drug-loaded nonpareil core, a sub-coating layer (HPMC 6cps) and an SR-coating layer (Aquacoat® ECD, Eudragit® RS 30D or Kollicoat® SR 30D) were prepared by a bottom-spray fluidized bed-coating method. The drug release from the dual-coated SR pellets coated with Aquacoat® ECD followed a zero-order profile in water, and the drug release was not affected by the coating level of the sub-coating layer and stable under the accelerated storage condition (40?°C, 75% RH) for 6 months. The CR preparation showed significantly decreased values of maximum drug concentration (C_max) and elimination rate (K) than the reference product (LEVOTUS® SYR) but the similar bioavailability (F?=?95.43%). The novel CR preparation presents promising delivery of LDP with an immediate and sustained release manner, with similar clinical effect as the commercial IR product.     

Controlled release of huperzine A from biodegradable microspheres: In vitro and in vivo studies

This paper describes the effect on Sun Protection Factor (SPF) of the combination of inorganic and organic filters in sunscreen products as determined by an in vitro method. O/W emulsions containing inorganic filters, such as titanium dioxide and zinc oxide, combined with 18 EU-authorized UV-B organic filters were tested. SPF measurements were carried out using a spectrophotometer equipped with an integrating sphere.

This study observed a synergic effect when titanium dioxide was combined with either anisotriazine or octyldimethylPABA. The combination of zinc oxide with 11 UV-B organic filters also exhibited a similar synergy; however, the measured SPF was systematically lower than the protection factor achieved with titanium dioxide.