Poly(DL-lactide-co-glycolide) microporous microsphere-based depot formulation of a peptide-like antineoplastic agent

In the present investigation, a poly(DL-co-glycolide) (PLGA)-based, microspheric depot system for bleomycin (BLM) has been formulated, and the same has been evaluated in-vivo in C57BL/6J mice bearing transplantable melanoma B16F1 murine solid tumour. The microparticulate delivery systems were formulated employing a water-in-oil-in-water (W/O/W) emulsion-solvent evaporation technique and characterized in-vitro. The microspheres were injected subcutaneously to form a drug depot at the site of injection in mice bearing experimental tumours and the drug was continuously infused into the systemic circulation with progressive biodegradation. The drug-loaded microspheres exhibited improved pharmacodynamic efficacy, as evidenced by retarded tumour growth kinetics. Preliminary pharmacokinetic studies illustrated controlled release of the drug into the systemic circulation over the study period to exert an anti-neoplastic action. These studies demonstrated the feasibility of employing a PLGA-based microparticulate system as an effective biodegradable, injectable, depot-forming therapeutic system for long-term administration of anti-neoplastic agents.     

Optimization and performance evaluation of peptide-loaded monolithic poly-epsilon-caprolactone microspheres in mice bearing melanoma B16F1

The objective of this investigation was to develop a bleomycin depot based on monolithic microparticulate technology to suppress tumour growth and to maintain constant plasma drug concentrations within an optimal therapeutic window over a prolonged period of time. Formulations were optimized with biodegradable poly-epsilon-carpolactone and evaluated in vitro for physicochemical characteristics, drug release in phosphate buffered saline (pH 7.4) and evaluated in vivo in tumour bearing mice. This investigation revealed that upon subcutaneous injection, the biodegradable depot-forming poly-epsilon-carpolactone microspheres controlled drug release and suppressed tumour growth kinetics significantly compared to control. A preliminary pharmacokinetic evaluation exhibited steady plasma drug concentrations during the study period. This formulation with its reduced frequency of administration and better control of drug disposition is expected to provide an economic benefit to the user compared with products currently available for chemotherapy.     

Transdermal microparticle delivery by a supersonic-Helios gun system

The effect of particle size and flow of helium gas on the systemic absorption of indomethacin by means of a needle-free injection system was investigated. Poly-L-lactic acid microspheres conaining indomethacin were prepared by the o/w solvent evaporation technique. Microspheres were accelerated by a stream of helium gas in the Helios gun system, and then delivered to the abdominal skin of male hairless rats. Delivery of indomethacin to rat skin proportionally increased with helium pressure (supersonic flow). Bioavailability and Cmax were also dependent on the helium pressure. This method can be used to deliver the drug and/or microparticulate systems into the skin tissues and systemic circulation.     

Enhanced targeting efficiency of PLGA microspheres loaded with Lornoxicam for intra-articular administration

Owing to its rationale of targeting the drug to the site of action and minimizing systemic toxic effects of the drug, intra-articular drug delivery system has gained growing interests. In this study, emphasis was placed on intra-articular Lornoxicam-loaded PLGA microspheres (Lnxc-PLGA-MS) preparation and improving the targeting of lornoxicam (Lnxc) in knee joint. The microspheres were prepared by a process involving solid-in-oil-in-water(S/O/W) emulsion, and evaluated for physicochemical properties. Joint cavity's drug leakage into systemic circulation in rabbits was examined to define the drug stagnation. Meanwhile, drug retention in synovial fluid in rats was investigated to further validate the drug targeting. The microspheres were spherical as evidenced by the SEM photographs with mean size of 7.47 μm, and encapsulation efficiency was observed 82.22% along with drug loading 12.17%. DSC revealed that the drug in the microspheres existed in the phase of uncrystallization. The formulated microspheres could prolong the drug release up to 32 days in vitro. Comparing with animals injected with lornoxicam solution, the plasma drug concentration decreased in rabbits and retention time increased in rats' synovial fluid with intra-articular injections of microspheres, revealing good targeting efficiency. In conclusion, PLGA microspheres could be used to deliver lornoxicam following intra-articular administration for enhancing targeting efficiency.     

Enhanced targeting efficiency of PLGA microspheres loaded with Lornoxicam for intra-articular administration

Owing to its rationale of targeting the drug to the site of action and minimizing systemic toxic effects of the drug, intra-articular drug delivery system has gained growing interests. In this study, emphasis was placed on intra-articular Lornoxicam -loaded PLGA microspheres (Lnxc-PLGA-MS) preparation and improving the targeting of lornoxicam (Lnxc) in knee joint. The microspheres were prepared by a process involving solid-in-oil-in-water(S/O/W) emulsion, and evaluated for physicochemical properties. Joint cavity′s drug leakage into systemic circulation in rabbits was examined to define the drug stagnation. Meanwhile, drug retention in synovial fluid in rats was investigated to further validate the drug targeting. The microspheres were spherical as evidenced by the SEM photographs with mean size of 7.47μm, and encapsulation efficiency was observed 82.22% along with drug loading 12.17%. DSC revealed that the drug in the microspheres existed in the phase of uncrystallization. The formulated microspheres could prolong the drug release up to 32 days in vitro. Comparing with animals injected with lornoxicam solution, the plasma drug concentration decreased in rabbits and retention time increased in rats’ synovial fluid with intra-articular injections of microspheres, revealing good targeting efficiency. In conclusion, PLGA microspheres could be used to deliver lornoxicam following intra-articular administration for enhancing targeting efficiency.     

超高速氦气系统经皮微球给药研究

目的　研究微球的粒子大小和超高速氦气气流的压力对释放固体微球经皮给药吸收过程的影响。方法利用氦气的超高速流体通过对固体粒子进行加速的方法,将药物粉末透过角质层释放到表皮和真皮表面,将固体药物粉末通过皮肤释放到体内。结果　药物导入率依赖于超高速氦气气流的压力和微球的粒子大小,且生物利用度和最高血中浓度也依赖于超高速氦气气流压力的影响。结论　本系统可用于固体药物粉末、多肽类药物、高分子药物以及蛋白性药物的经皮给药。     

Polymeric microparticles-based formulation for the eradication of cutaneous candidiasis: development and characterization

Abstract

Cutaneous candidiasis is a common topical fungal infection which may be more prominent in patients associated with AIDS. It is usually treated by conventional formulations such as cream, gel, which show various adverse effects on skin along with systemic absorption. To overcome these drawbacks, various novel drug delivery systems have been explored. Poly(lactic-co-glycolic acid) (PLGA)-based microparticulate systems have shown good dermal penetration after topical application. Therefore, in the present study clotrimazole-loaded PLGA microspheres were prepared for targeted dermal delivery. Microspheres were prepared by using a single emulsification (oil-in-water, O/W) evaporation technique and characterized for different parameters. Prepared microparticulate systems were dispersed in Carbopol 934® gel and antifungal activity was carried out on experimentally induced cutaneous candidiasis in immunosuppressed guinea pigs. Particle size of optimized formulation was 2.9?µm along with 74.85% entrapment of drug. Skin retention studies revealed that drug accumulation in the skin was higher with microspheres gel as compared to marketed gel. Confocal microscopy of skin further confirmed penetration of microspheres up to 50?µm into the dermal region. In-vivo antifungal activity studies demonstrated that microsphere gel showed better therapeutic activity, lowest number of cfu/ml was recorded, as compared to marketed gel after 96?h of application. Based on the results of the study, it can be concluded that PLGA microparticles may be promising carriers to deliver clotrimazole intradermally for the treatment of invasive fungal infections.     

In vitro evaluation of chondroitin sulphate-chitosan microspheres as carrier for the delivery of proteins

A novel formulation based on chondroitin sulphate/chitosan microspheres (CS/CH) has been investigated for oral delivery of macromolecules using ovalbumin as the model protein (OVA). The microspheres were prepared by a new emulsion-complex coacervation method. Physico-chemical properties of the polymers constituting microparticulate matrix were investigated by IR, DSC, TGA and X-ray diffraction analyses. In vitro tests were performed to evaluate the drug delivery system degradation and the protein release under conditions simulating the intestinal fluids. The ability of colonic enzymes to degrade the microparticulate systems was simulated employing the chondroitinase ABC enzyme. Results showed that the different CS/CH compositions influenced both microparticles stability and the protein release rate. Only the microspheres composed by 1:1 chondroitin sulphate–chitosan ratio achieved an OVA release profile suitable to a possible colon targeting. These microspheres released ～30% of ovalbumin encapsulated in 24 h in the different aqueous media tested, while they released 100% of protein in the presence of chondroitinase. The preliminary results demonstrated that chondroitin sulphate-chitosan microspheres can be a suitable delivery system for protein drug envisaged to oral administration.     

In vitro evaluation of chondroitin sulphate-chitosan microspheres as carrier for the delivery of proteins

A novel formulation based on chondroitin sulphate/chitosan microspheres (CS/CH) has been investigated for oral delivery of macromolecules using ovalbumin as the model protein (OVA). The microspheres were prepared by a new emulsion-complex coacervation method. Physico-chemical properties of the polymers constituting microparticulate matrix were investigated by IR, DSC, TGA and X-ray diffraction analyses. In vitro tests were performed to evaluate the drug delivery system degradation and the protein release under conditions simulating the intestinal fluids. The ability of colonic enzymes to degrade the microparticulate systems was simulated employing the chondroitinase ABC enzyme. Results showed that the different CS/CH compositions influenced both microparticles stability and the protein release rate. Only the microspheres composed by 1:1 chondroitin sulphate-chitosan ratio achieved an OVA release profile suitable to a possible colon targeting. These microspheres released approximately 30% of ovalbumin encapsulated in 24 h in the different aqueous media tested, while they released 100% of protein in the presence of chondroitinase. The preliminary results demonstrated that chondroitin sulphate-chitosan microspheres can be a suitable delivery system for protein drug envisaged to oral administration.     

One- and three-month release injectable microspheres of the LH-RH superagonist leuprorelin acetate

The biodegradable polymers poly(lactic/glycolic acid) (PLGA) and poly(lactic acid) (PLA) were used as wall materials in the preparation of microspheres (msp) containing the LH-RH superagonist leuprorelin (leuprolide) acetate. A novel W/O/W emulsion-solvent evaporation method was devised for the preparation of msp containing this water-soluble peptide. This method achieved high entrapment efficiency and sustained drug release over a long period predominantly due to polymer bioerosion. The msp are fine microcapsules with polycores containing the peptide at a high concentration and are easily injectable through a conventional fine needle. Leuprorelin msp made with PLGA(75/25)-14,000 or PLA-15,000 released the drug in a zero-order fashion, maintained constant serum drug levels and attained persistent objective suppression of the pituitary-gonadal system ('chemical castration') over 1 or 3 months after i.m. or s.c. injection into animals. These results indicate that depot formulations may be potentially useful in the therapy of endocrine diseases in humans. In this paper, studies on the formulation, drug release and pharmacological effects in animals for these leuprorelin depot formulations are reviewed.     

Particle size and loading efficiency of poly(D,L-lactic-coglycolic acid) multiphase microspheres containing water soluble substances prepared by the hydrous and anhydrous solvent evaporation methods

PLGA multiphase microspheres were prepared by the multiple emulsion solvent evaporation method using acetonitrile as the polymer solvent and mineral oil as the evaporation medium. The preparation process was further developed in the present study to reduce the particle size and to increase the loading capacity of brilliant blue, bovine serum albumin (BSA) and tumour necrosis factor-alpha (TNF-alpha) which were used as water soluble model drug substances. Sorbitan sesqui-oleate (SO-15EX), present at the 1% w/w level in the evaporation medium, prevented agglomeration of the microspheres containing a solid-in-oil (S/O) suspension as the core phase. This S/O suspension core provided significantly higher loading efficiency of the proteins to the W/O emulsion core. The W/O emulsion system resulted in agglomeration of the protein-loaded microspheres and the loading efficiency decreased significantly. When brilliant blue was included as the model compound, the loading efficiencies were not influenced by the core type. Heavy mineral oil was employed to stabilize the dispersed unhardened microspheres rather than light mineral oil that was reported previously. This anhydrous emulsion system employing the S/O suspension core and containing a dispersion of TNF-alpha enabled the encapsulation of this protein without loss of activity. It was concluded that the anhydrous emulsion system is asuitable approach toprepare multiple microspheres as an alternative to the W/O emulsion system, especially when solvent sensitive proteins are incorporated into the microspheres.     

Delivery of an anticancer drug and a chemosensitizer to murine breast sarcoma by intratumoral injection of sulfopropyl dextran microspheres

Intratumoral injection of controlled-release microsphere formulations of anticancer compounds has the potential to selectively increase tumour exposure to drugs. This work aimed to evaluate the therapeutic effect and toxicity of microsphere formulations containing the anticancer drug, doxorubicin, in a murine tumour model. The effect of co-administration of verapamil, a P-glycoprotein modulator or chemosensitizer, was investigated. Initial in-vitro studies confirmed the ability of verapamil to enhance the accumulation of both doxorubicin and [(99mTc)]sestamibi, also a P-glycoprotein substrate, in EMT6 murine breast sarcoma cells and a doxorubicin-selected multidrug-resistant variant, EMT6/AR1.0. Ex-vivo studies using confocal microscopy demonstrated release of doxorubicin from microspheres and diffusion of the drug through tissue. For in-vivo studies, EMT6 and EMT6/AR1.0 cells were grown in BALB/c mice. Following intratumoral injection of doxorubicin-loaded microspheres, alone or in combination with verapamil-loaded microspheres, the tumour diameter was measured serially as an indication of therapeutic effect, while the weight, appearance, and behaviour of the mice were monitored as an indication of general toxicity. Intratumoral injections of doxorubicin-loaded microspheres were tolerated much better than systemic administration of equivalent drug concentrations. There was a modest (up to 34%) delay of tumour growth compared with groups receiving no treatment or blank microspheres. Co-injection of verapamil microspheres with doxorubicin microspheres produced a moderate increase in toxicity but no further delay in tumour growth. Controlled-release microsphere formulations of anticancer agents administered intratumorally were an efficient way to deliver high drug doses to the tumour with little systemic toxicity.     

Preparation and in vitro evaluation of thiolated chitosan microparticles

The objective of this study was to prepare a microparticulate drug delivery system being based on a new thiomer, namely a chitosan 2-iminothiolane conjugate (chitosan-TBA conjugate). Due to thiol groups being immobilized on chitosan, chitosan-TBA conjugate exhibits improved mucoadhesive and permeation enhancing properties. Because of these features microparticulate drug delivery systems based on chitosan-TBA conjugate might be a promising tool for the non-invasive administration of hydrophilic macromolecular drugs. Chitosan-TBA conjugate microspheres were prepared by the emulsification/solvent evaporation method. Fluorescein-isothiocyanate labelled dextran (FITC-dextran) was chosen as a model hydrophilic drug. Microspheres have been characterized by morphological analysis, thiol group content, swelling behaviour, polymer degradation drug load determination, dissolution test and mucoadhesion studies. Results reported in this work demonstrated the possibility to obtain stable microspheres without cross-linking agents. Thiolated chitosan microspheres seem to be more stable in aqueous media with respect to unmodified chitosan. The degradability by lysozyme appears quite similar for both polymers, showing that chemical modification does not influence the biodegradable properties of chitosan. Microspheres were able to control the drug release for at least 1?h, exhibiting comparatively strong mucoadhesive properties. The chitosan-TBA conjugate microparticles remain on the mucosa in a 2.5-fold higher concentration with respect to unmodified chitosan microparticles. These data suggest that chitosan-TBA conjugate microspheres have the potential to be used as a mucoadhesive drug delivery system.     

Preparation and in vitro evaluation of thiolated chitosan microparticles

The objective of this study was to prepare a microparticulate drug delivery system being based on a new thiomer, namely a chitosan 2-iminothiolane conjugate (chitosan-TBA conjugate). Due to thiol groups being immobilized on chitosan, chitosan-TBA conjugate exhibits improved mucoadhesive and permeation enhancing properties. Because of these features microparticulate drug delivery systems based on chitosan-TBA conjugate might be a promising tool for the non-invasive administration of hydrophilic macromolecular drugs. Chitosan-TBA conjugate microspheres were prepared by the emulsification/solvent evaporation method. Fluorescein-isothiocyanate labelled dextran (FITC-dextran) was chosen as a model hydrophilic drug. Microspheres have been characterized by morphological analysis, thiol group content, swelling behaviour, polymer degradation drug load determination, dissolution test and mucoadhesion studies. Results reported in this work demonstrated the possibility to obtain stable microspheres without cross-linking agents. Thiolated chitosan microspheres seem to be more stable in aqueous media with respect to unmodified chitosan. The degradability by lysozyme appears quite similar for both polymers, showing that chemical modification does not influence the biodegradable properties of chitosan. Microspheres were able to control the drug release for at least 1 h, exhibiting comparatively strong mucoadhesive properties. The chitosan-TBA conjugate microparticles remain on the mucosa in a 2.5-fold higher concentration with respect to unmodified chitosan microparticles. These data suggest that chitosan-TBA conjugate microspheres have the potential to be used as a mucoadhesive drug delivery system.     

Protein loaded biodegradable microspheres based on PLGA-protein bioconjugates.

Biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) was chemically conjugated to lysozyme, a model protein drug, by coupling a terminal carboxylic acid in PLGA with primary amine groups present in lysozyme. The conjugation was carried out in dimethylsulphoxide (DMSO) by using carbodiimide as a coupling agent. The PLGA-lysozyme conjugate, dissolved in a co-solvent system of DMSO and methylene chloride, was directly formulated into microspheres by an oil-in-water (O/W) single emulsion solvent evaporation technique. Morphological characteristics of the resultant microspheres, loading efficiencies, and protein release behaviours with protein instability problems were investigated in comparison with those of the microspheres prepared by water-in-oil-water (W/O/W) double emulsion and O/W single emulsion techniques which employed PLGA with unconjugated lysozyme for the formulation.     

Biodegradable microspheres of curcumin for treatment of inflammation

Curcumin, a natural constituent of Curcuma longa (turmeric, CAS 458-37-7) was formulated as prolonged release biodegradable microspheres for treatment of inflammation. Natural biodegradable polymers, namely, bovine serum albumin and chitosan were used to encapsulate curcumin to form a depot forming drug delivery system. Microspheres were prepared by emulsion-solvent evaporation method coupled with chemical cross-linking of the natural polymers. Curcumin could be encapsulated into the biodegradable carriers upto an extent of 79.49 and 39.66% respectively with albumin and chitosan. Different drug:polymer ratios did not affect the mean particle size or particle size distribution significantly. However, the concentration of the crosslinking agent had remarkable influence on the drug release. In-vitro release studies indicated a biphasic drug release pattern, characterized by a typical burst-effect followed by a slow release which continued for several days. Evaluation of antinflammatory activity using Freund's adjuvant induced arthritic model in Wistar rats revealed significant difference between both the formulations, albumin microspheres and chitosan micropheres as well as against control. It was evident from the present study that the curcumin biodegradable microspheres could be successfully employed as prolonged release drug delivery system for better therapeutic management of inflammation as compared to oral or subcutaneous route.     

In vitro and in vivo evaluation of ranitidine hydrochloride ethyl cellulose floating microparticles

The real issue in the development of oral controlled release dosage forms is not just to prolong the delivery of drugs but also to prolong the presence of dosage forms in the stomach in order to improve the bioavailability of drugs with a 'narrow absorption window'. In the present study, an anti-ulcer drug, ranitidine hydrochloride, is delivered through a gastroretentive ethyl cellulose-based microparticulate system capable of floating on simulated gastric fluid for > 12 h. Preparation of microparticles is done by solvent evaporation technique with modification by using an ethanol co-solvent system. The formulated microspheres were free flowing with good packability and encapsulation efficiencies were up to 96%. Scanning electron microscopy confirmed porous, spherical particles in the size range 300-750 microm. Microspheres showed excellent buoyancy and a biphasic controlled release pattern with 12h. In vivo bioavailability studies performed on rabbits and T(max), C(max), AUC were calculated and confirmed significant improvement in bioavailability. The data obtained thus suggests that a microparticulate floating delivery system can be successfully designed to give controlled drug delivery, improved oral bioavailability and many other desirable characteristics.     

Preparation and characterization of fentanyl-loaded PLGA microspheres: in vitro release profiles

We developed several kinds of fentanyl-loaded poly(L-lactide-co-glycolide) (PLGA) microspheres (FMS) for sustained release of fentanyl. FMS were prepared by an emulsion solvent-evaporation method. In this study, the influences of several preparation parameters, such as initial drug loading, polymer concentration, and solvent volume on the release patterns of fentanyl were investigated. Furthermore, it has been well noted that the detection of fentanyl is extremely difficult because its clinical dose level is very low, about 1-3 ng/ml, in cancer-patient treatment. Therefore, we also developed a rapid and sensitive determination method for fentanyl in systemic circulation by employing gas chromatography (GC) system. Fentanyl was slowly released from FMS over 15 days with a quasi-zero order property. From the results, our FMS may be good formulations to deliver the analgesics and suitable for the treatment of severe pain over long periods.     

Controlled release chitosan microspheres of mirtazapine: In vitro and in vivo evaluation

The purpose of the study was to formulate and evaluate controlled release chitosan microspheres of mirtazapine (MTZ) to improve the bioavailability by altering the pharmacokinetic profiles of the drug. Chitosan microspheres were prepared to prolong the release of the drug into the systemic circulation. Microspheres were prepared by a single water in oil (w/o) emulsion technique varying the chitosan/drug ratio, stirring speed and concentration of the crosslinking agent (glutaraldehyde). Drug-polymer compatibility studies were carried out using fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The microspheres were evaluated for encapsulation efficiency, particle size, surface morphology, swelling index, in vitro release, as well as erosion and in vivo studies in rats. The FT-IR and DSC studies revealed no interaction between drug and polymer. The encapsulation efficiency of different formulation varied from 53 ± 1.2% to 78 ± 1.5%. The mean particle size of the optimized formulation F-14 was 106.4 ± 0.5 μm. Surface morphology revealed that chitosan microspheres were discrete and spherical in shape with a porous surface. The release of MTZ from chitosan microspheres was rapid up to 4 h, and then it was continuously and slowly released up to 48 h. Optimized formulation (F-14) was found to be stable under accelerated storage conditions based on International Conference on Harmonisation guidelines. Pharmacokinetic studies revealed that the optimized formulation showed significant increases in systemic exposure (AUC = 177.70 ± 7.39 μg·h/mL), half-life (4.72 ± 0.46 h) and reduced clearance (0.009 ± 0.0001 L/h) compared to pure drug administration. Hence, the present study demonstrates that controlled release formulation of MTZ microspheres using chitosan can improve pharmacokinetic profiles of MTZ.     

Sustained Suppression of the Pituitary-Gonadal Axis by Leuprorelin Three-Month Depot Microspheres in Rats and Dogs

The pharmacological effects of leuprorelin three-month depot microspheres were investigated in rats and dogs. After s.c. and i.m. injection, the microspheres provided similar linear drug release and sustained serum drug levels for 3 months. Persistent suppression of serum LH, FSH (in rats) and testosterone (in rats and dogs) for over 16 weeks was achieved when the microspheres were given at a dose of 100 (rat) and 25.6 (dog) µg/kg/day. These hormone release responses upon periodic challenge tests revealed that a single injection of the microspheres caused dramatic suppression of the function of the pituitary-gonadal system for 15 weeks in rats. The growth of the genital organs was also suppressed dose-dependently by injection of the microspheres over 3 months; the strongest suppression was achieved at a dose of 100 µg/kg/day. This three-month depot formulation is expected to be more convenient than the one-month depot with improved patient compliance and therapeutic effects.