A local delivery system for fentanyl based on biodegradable poly(L-lactide-co-glycolide) oligomer

Preparation of porous PLGA microspheres with thermoreversible gel to modulate drug release profile of water-soluble drug: bleomycin sulphate

Bleomycin sulphate-loaded porous microspheres were prepared using modified solvent evaporation method (w/o/w) using PLGA50:50 as a polymeric system. The prepared microspheres were incorporated in pluronic (F127) based thermoreversible gel to develop a depot formulation. Various process parameters as solvent evaporation temperature and formulation parameters such as surfactant concentration, volume of internal and external phase and drug-to-polymer ratio were optimized for enhancing percentage drug entrapment, percentage drug loading and desired release profile by controlling size and porosity of the microspheres. Microspheres were characterized for particle size, zeta potential, surface morphology, percentage drug loading and in vitro drug release study after incorporated in gel. The formulated microspheres were porous in nature and showed biphasic in vitro drug release profile. The microspheres incorporated in pluronic (F127) gel showed sustained release up to 1 week and may be useful for treatment of squamous cell carcinoma with better therapeutic effect.

Materials for pharmaceutical dosage forms: molecular pharmaceutics and controlled release drug delivery aspects

Controlled release delivery is available for many routes of administration and offers many advantages (as microparticles and nanoparticles) over immediate release delivery. These advantages include reduced dosing frequency, better therapeutic control, fewer side effects, and, consequently, these dosage forms are well accepted by patients. Advances in polymer material science, particle engineering design, manufacture, and nanotechnology have led the way to the introduction of several marketed controlled release products and several more are in pre-clinical and clinical development.

Influence of ultrasonic processing on the macromolecular properties of poly (D,L-lactide-co-glycolide) alone and in its biocomposite with hydroxyapatite

In this work poly(D,L-lactide-co-glycolide) (PLGA) and a poly(d,l-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) composite processed in an ultrasonic field at higher (25 degrees C) and lower (8 degrees C) temperatures were studied with respect to the molecular properties of the obtained materials. The processing of the PLGA and the PLGA/HAp composite in an ultrasonic field resulted in a change of molar mass averages of the polymer/polymeric part of these materials, while an amorphous structure and a 50:50 lactide-to-glycolide co-monomer ratio were preserved without the formation of crystalline oligomers. However, mobility of polymeric chains obtained after ultrasonic processing was lower indicating ordering the structure of polymeric chains as a result of processing. Additionally, it was observed that the mobility of the PLGA macromolecules was lower within the composite in comparison with the mobility of the chains within the PLGA alone in the case when both were obtained after ultrasonic processing. This was a consequence of the structure formation through the interactions between the PLGA and the HAp. Based on these results different degradation rate of PLGA in composite can be expected, which is important in the application of this material for the controlled drug delivery of medicaments.

Formulation and characterization of injectable poly(DL-lactide-co-glycolide) implants loaded with N-acetylcysteine, a MMP inhibitor

PURPOSE

The objective of this study was to develop poly(lactic-co-glycolic acid) (PLGA) injectable implants (i.e., millicylinders) with microencapsulated N-acetylcysteine (NAC) for site-specific controlled NAC release, for potential chemopreventive applications in persons with previously excised head and neck cancers.

METHODS

PLGA 50:50 (i.v.=0.57 dl/g) implants with 1-10 wt% NAC free acid or 10 wt% NAC salts (NAC-Na+, NAC-Mg2+ and NAC-Ca2+) were prepared by solvent extrusion and/or fluid energy micronization (FEM) methods. X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) studies were performed to evaluate the physical mixing of NAC with PLGA. PLGA implant degradation was studied by kinetics of polymer molecular weight decline (gel permeation chromatography) and mass loss. Release studies were conducted in N2 purged PBS (pH 7.4) at 37 degrees C in evacuated and sealed ampoules. NAC was quantified by HPLC at 210 nm.

RESULTS

XRD, SEM and DSC studies indicated that NAC had dissolved in the polymer phase at 1-3.5% w/w loading, but became discretely suspended in the polymer at 6-10% w/w. Initial burst and long-term release rate increased with increased drug loading, and release was uncharacteristically rapid at higher loading (6-10% w/w). The cause of the rapid release was linked to extensive plasticization, matrix porosity and general acid catalysis of PLGA degradation caused by the NAC free acid. PLGA millicylinders loaded with 10% w/w NAC-Ca2+ and NAC-Mg2+salts exhibited reduced burst (34 vs 13-22% release within a day of incubation for NAC free acid vs NAC-Ca2+ and NAC-Mg2+salts, respectively) and slow and continuous complete release over 4 weeks without significant NAC-catalyzed degradation of PLGA. Release of NAC from NAC-Ca2+/PLGA implant was slower than that of NAC-Mg2+/PLGA consistent with the lower solubility of the former salt. NAC with its free thiol was rapidly converted to its cystine dimer in the presence of molecular oxygen. PLGA released samples in sealed and evacuated ampoules indicated>80% parent NAC remaining after the 1 month release analysis irrespective of initial NAC free acid and salt forms.

CONCLUSION

By encapsulating the NAC-Mg2+ and NAC-Ca2+ salts in PLGA implants, the high initial burst, short release duration, and the general acid catalysis caused by the NAC free acid were each prevented and 1-month slow and continuous release was attained with minimal instability of the free thiol group.

Polymer-based biodegradable drug delivery systems in pain management

Pain is an unpleasant sensory experience commonly produced by damage to bodily tissues and it is one of the most significant public health problems, because 21.5% of the world population is estimated to suffer from pain. It results in a total loss of more than 165 billion US dollars each year in the United States alone. Pain reflects a mixture of various pathophysiologic, psychologic, and genetic contributions. When undertreated, pain usually results in serious immune and metabolic upset. Therefore, it requires wide understanding and intensive effort for a better management. Currently, pain control is limited by the modest efficiency of the used drugs, the serious side effects of these drugs, and the inefficacy of conventional drug administration. By the introduction of the technology of biodegradable controlled-release devices into clinical practice, pain control not only benefits from these novel methods for a better delivery of various drugs, but the side effects of the drugs are reduced because use of the devices improves patient compliance. Biodegradable controlled-release devices are polymer-based devices that are designed to deliver drugs locally in a predesigned manner. Recently, there was a high interest in developing these devices for the delivery of different drugs used for pain control. This paper first highlights the dimensions and basics of the problem of pain. Then, it presents an overview of the biodegradable polymers that are used in drug delivery systems and summarizes the studies carried out on these systems in the field of pain management. We refer to our experience in developing a device for multimodal drug delivery, including the use of nanotechnology. Future perspectives are also presented.

Optimisation and characterisation of bioadhesive controlled release tetracycline microspheres

A Box-Behnken experimental design was employed to statistically optimise the formulation parameters of a tetracycline microsphere preparation for maximum bioadhesivity and controlled drug release. The quantitative effect of the formulation parameters at different levels on bioadhesion and drug release could be predicted using polynomial equations. A formulation comprising of 3% (w/w) chitosan, 10% (w/w) tetracycline HCl and 9% (w/v) tripolyphosphate was identified for maximising bioadhesivity and obtaining controlled drug release. The optimal microsphere preparation was subsequently characterised in terms of hydration dynamics, release kinetics, antimicrobial activity, thermal properties, morphology and surface pH. Kinetic models revealed that drug release followed Fickian diffusion while textural analysis showed minimal hydration over the test period. Antimicrobial studies showed that the drug concentrations in the in vitro release samples were above the minimum concentration of drug required for inhibition of Staphylococcus aureus growth. Thermal analyses showed a possible interaction between the drug and polymer. Scanning electron microscopy confirmed the integrity of the microspheres and identified the morphological changes following drug release. Surface pH of the microspheres was similar to salivary pH and did not show extremes in changes over the test period.

Controlled release of paclitaxel from microemulsion containing PLGA and evaluation of anti-tumor activity in vitro and in vivo

The main objective of this study was to develop an optimal paclitaxel microemulsion prepared by self-microemulsifying drug delivery system (SMEDDS) which is a mixture of paclitaxel, tetraglycol, Cremophor ELP, and Labrafil 1944 and a paclitaxel microemulsion containing poly(D,L-lactide-co-glycolide) (PLGA) in order to offer controlled release of paclitaxel. To achieve this goal, paclitaxel and PLGA were dissolved by solubilizer like tetraglycol. There was not observed any change in molecular weight of PLGA after being solubilized by tetraglycol. The droplet size for all of the formulation of microemulsion was found in the range of 45-270nm by dynamic light scattering (DLS). It was observed that the droplet size of microemulsion without PLGA was smaller than that of microemulsion containing PLGA by transmission electron microscopy (TEM). The droplet of microemulsion containing PLGA was almost of spherical shape with smooth surface and there was no aggregation or adhesion among droplet of microemulsion by atomic force microscopy (AFM). The release behaviour of paclitaxel from microemulsion containing PLGA having various molecular weights (8K, 33K, and 90K) exhibited a biphasic pattern characterized by a fast initial release during the first 48h, followed by a slower and continuous release for 144h, in contrast that the release of paclitaxel from microemulsion without PLGA was finished during 24h. This result was identical with the result of anti-tumor activity in vitro of paclitaxel from microemulsion containing PLGA against human breast cancer cell line MCF7 and this formulation enhanced anti-tumor activity in vivo compared with microemulsion without PLGA against SKOV-3 human ovarian cancer cells bearing nude mice model.

Hydrolytic degradation of poly(lactide-co-glycolide) films: effect of oligomers on degradation rate and crystallinity

Oligomers are thought to accelerate the hydrolytic degradation of devices prepared from poly(lactide-co-glycolide), PLGA, due to their increased number of carboxylic end groups. To experimentally verify this hypothesis, two D,L-lactic acid oligomers having molecular weights close to their critical limit of solubility were synthesized and incorporated into PLGA films in three concentrations (0, 10, and 30% w/w). All films were translucent, rather flexible and initially amorphous. With increasing oligomer concentration the glass transition temperature (T(g)) and the molecular weight of films decreased prior to erosion. The degradation studies show that initial mass loss and water absorption are increased in oligomer-containing films as a function of average molecular weight and oligomer concentration. However, the incorporation of oligomers does not accelerate the degradation of films. By contrast, oligomer-containing films show extended lag phase until onset of polymer erosion. This was shown to be related to crystallization. Moreover, it was found that crystallization occurs earlier in oligomer-containing films and that the degree of crystallization is related to the average molecular weight of the oligomer. These findings bring new insight into the role of oligomers in the degradation process and can be used to explain why erosion in massive polymer devices occurs from the center to the surface.