Biodegradable cisplatin microspheres for direct brain injection: preparation and characterization

Multi-vesicular Liposome and its Applications: A Novel Chemically Modified Approach for Drug Delivery Application

BACKGROUND

This study aimed to elaborate on all the aspects of multivesicular liposomes, including structure, function, topology, etc. Liposomes are a unique drug delivery system, in which both hydrophilic and hydrophobic drug molecules can be incorporated. Particularly, multivesicular liposomes have more advantages than other liposomes because of their unique structure. This study provides an overview of several works already performed by various researchers in this field. Numerous studies have reported on preparing and evaluating multivesicular liposomes for drug delivery applications. This study summarizes the process of formulating multivesicular liposomes and their application in drug delivery systems and provides details about how to resolve the problem of limited solubility and stability of biomolecules, along with controlled drug release kinetics, with the possibility of loading various drugs. There is no doubt that multivesicular liposome opens new avenues to develop novel drug delivery system for achieving the desired functional performances and expanding the applications in the drug delivery area.

Intratumoral delivery of paclitaxel-loaded poly(lactic-co-glycolic acid) microspheres for Hep-2 laryngeal squamous cell carcinoma xenografts

The introduction of induction chemotherapy provides an expectation of laryngeal function preservation without reduction in survival for patients with advanced laryngeal squamous cell carcinoma. The antitumor activity of conventional intravenous chemotherapy, however, is limited by systemic toxicity. The polymeric drug system delivered locally provides a novel modality of increasing therapeutic concentrations of drug for a prolonged period while decreasing systemic levels. In the current study, paclitaxel-loaded sustained-release microspheres were developed using poly(lactic-co-glycolic acid) as a drug carrier. Intratumoral administration of paclitaxel in the formulation of polymer showed enhanced efficacy against laryngeal squamous cell carcinoma in nude mice compared with conventional paclitaxel injection via the intratumoral or intraperitoneal route. No significant toxic reactions were observed in the experiment. Immunohistochemical findings indicated that paclitaxel exhibited antiangiogenic activity by inhibiting the expression of basic fibroblast growth factor and vascular endothelial growth factor within the tumor. Moreover, this effect could be better exploited via localized delivery of polymeric paclitaxel. In conclusion, direct administration of polymeric drug system at the tumor sites proved to be promising for the treatment of laryngeal carcinoma.

Process and formulation variables in the preparation of injectable and biodegradable magnetic microspheres

The aim of this study was to prepare biodegradable sustained release magnetite microspheres sized between 1 to 2 microm. The microspheres with or without magnetic materials were prepared by a W/O/W double emulsion solvent evaporation technique using poly(lactide-co-glycolide) (PLGA) as the biodegradable matrix forming polymer. Effects of manufacturing and formulation variables on particle size were investigated with non-magnetic microspheres. Microsphere size could be controlled by modification of homogenization speed, PLGA concentration in the oil phase, oil phase volume, solvent composition, and polyvinyl alcohol (PVA) concentration in the outer water phase. Most influential were the agitation velocity and all parameters that influence the kinematic viscosity of oil and outer water phase, specifically the type and concentration of the oil phase. The magnetic component yielding homogeneous magnetic microspheres consisted of magnetite nanoparticles of 8 nm diameter stabilized with a polyethylene glycole/polyacrylic acid (PEG/PAA) coating and a saturation magnetization of 47.8 emu/g. Non-magnetic and magnetic microspheres had very similar size, morphology, and size distribution, as shown by scanning electron microscopy. The optimized conditions yielded microspheres with 13.7 weight% of magnetite and an average diameter of 1.37 microm. Such biodegradable magnetic microspheres seem appropriate for vascular administration followed by magnetic drug targeting.

Sustained release of cisplatin from multivesicular liposomes: potentiation of antitumor efficacy against S180 murine carcinoma

Cisplatin was encapsulated into multivesicular liposomes (MVLs) and the entrapment efficiency, size distribution, and in vitro drug release characteristics of the cisplatin-MVLs were studied. Pharmacokinetics, tissue distribution, and therapeutic efficacy of cisplatin-MVLs were compared against injection of cisplatin solution into mice inoculated with the murine carcinoma 180 (S180) tumor. The results showed that the cisplatin-MVLs were capable of high drug loading (0.148:1 mg cisplatin/mg lipid) and high encapsulation efficiency (>80%). The mean diameter of cisplatin-MVLs was 17 microm. In vitro studies of cisplatin-MVLs in saline solution showed that they sustained release of encapsulated drug for >7 days. Cisplatin-MVLs showed higher drug accumulation in the liver, spleen, and tumor regions than cisplatin solution, as well as higher plasma concentrations and a longer circulation time. The therapeutic efficacy of the cisplatin-MVL preparation against S180 tumor-bearing mice is significantly higher than that of cisplatin solution.

Kinetics of a model nucleoside (guanosine) release from biodegradable poly(DL-lactide-co-glycolide) microspheres: a delivery system for long-term intraocular delivery

The objective of this study was to prepare poly(DL-lactide-co-glycolide) (PLGA) microspheres containing guanosine as a model drug for intraocular administration. Microspheres were prepared by solvent evaporation technique using o/w emulsion system. The influence of composition and molecular weight of PLGA, drug loading efficiency, microsphere size, and in vitro and in vivo release rates were determined. Differential scanning calorimetry (DSC) and FTIR studies were conducted to examine the guanosine-polymer interaction. In vitro release studies indicated that the permeant release from microspheres exhibits an initial burst followed by slow first-order kinetics. Ascending molecular weights of the polymers generated progressively slower release rates. Three different sizes of microspheres were prepared. The release continued for 7 days with a maximum of 70% of the content released within that time period. DSC and FTIR studies showed no polymer-guanosine interaction. A novel microdialysis technique was used to examine the initial release kinetics from microspheres in isolated vitreous humor. This technique was also employed to observe in vivo intravitreal release in albino rabbits. A good correlation exists between in vitro and in vivo release rates from both 75 and 140 kDa PLGA microspheres. Guanosine-loaded microspheres could be prepared for once-a-week intravitreal injection with minimum required concentration maintained throughout the dosing interval. Because the structural and solubility characteristics of guanosine are similar to those of acyclovir and ganciclovir (two acycloguanosine analogues effective against herpes simplex virus [HSV-1] and cytomegalovirus [CMV], respectively), similar biodegradable polymer-based microsphere technology can be employed for the long-term intraocular delivery of these two drugs.

Application of membrane-based dendrimer/DNA complexes for solid phase transfection in vitro and in vivo

In this study a general description of the use of solid support membranes as the device for DNA delivery mediated by PAMAM dendrimers is presented. In contrast to the other DNA carriers, dendrimer/DNA complexes retain the ability to transfect after drying, which enabled coating or incorporation of complexes into poly(DL-lactide-co-glycolide) or collagen-based bioerodable membranes. These studies provide support for the use of this technology for in vitro and in vivo transfection of skin cells. Expression of luciferase or green fluorescent protein from pCF1-Luc and pEGFP1 plasmids indicated that dendrimer/DNA complexes can mediate transfection after dissociation from the solid support and/or when retained on the surface of the membranes. Modification of the membranes by incorporation of an anionic lipid, phosphatidyl glycerol (PG) at 1-5% concentrations, resulted in more efficient in situ transfection, particularly with dendrimer/DNA complexes formed at the low charge ratios (1-5). We also report data supporting the feasibility of membrane-based dendrimer/DNA complexes, particularly formed at lower than neutralizing conditions, for topical in vivo delivery of DNA to hairless mouse skin.

Development of microspheres for neurological disorders: from basics to clinical applications

Drug delivery to the central nervous system remains a challenging area of investigation for both basic and clinical neuroscientists. Numerous drugs are generally excluded from blood to brain transfer due to the negligible permeability of the brain capillary endothelial wall, which makes up the blood brain barrier in vivo. For several years, we have explored the potential applications of the microencapsulation of therapeutic agents to provide local controlled drug release in the central nervous system. Due to their size, these microparticles can be easily implanted by stereotaxy in discreet, precise and functional areas of the brain without damaging the surrounding tissue. This type of implantation avoids the inconvenient insertion of large implants by open surgery and can be repeated if necessary. We have established the compatibility of poly(lactide-co-glycolide) microspheres with brain tissues. Presently, the most developed applications concern Neurology and Neuro-oncology, with local delivery of neurotrophic factors and antimitotic drugs into neurodegenerative lesions and brain tumours, respectively. The drugs that had been encapsulated by our group included nerve growth factor (NGF), 5-fluorouracil (5-FU), idoxuridine and BCNU. Preclinical studies have been performed with each drug. Studies with NGF are reported as an example. A phase I/II clinical trial has been carried out in patients with newly diagnosed glioblastomas to assess the potentialities of 5-FU-loaded microspheres when intracranially implanted.

Allogeneic astrocytoma in immune competent dogs

We have induced in canines long-term immune tolerance to an allogeneic cell line derived from a spontaneous canine astrocytoma. Allogeneic astrocytoma cells were implanted endoscopically into the subcutaneous space of fetal dogs before the onset of immune competency (< 40th gestational day). At adulthood, dogs rendered tolerant successfully serve as recipients of intracranial transplants of their growing allogeneic, subcutaneous tumor. Transplanted dogs subsequently develop a solid brain tumor with histological features similar to the original astrocytoma. This model may allow rapid development and evaluation of new therapies for brain tumors, as well as afford tumor biology studies that are untenable in smaller, immune incompetent, or inbred animals harboring less representative tumors.

Controlled drug delivery by biodegradable poly(ester) devices: different preparative approaches

There has been extensive research on drug delivery by biodegradable polymeric devices since bioresorbable surgical sutures entered the market two decades ago. Among the different classes of biodegradable polymers, the thermoplastic aliphatic poly(esters) such as poly(lactide) (PLA), poly(glycolide) (PGA), and especially the copolymer of lactide and glycolide referred to as poly(lactide-co-glycolide) (PLGA) have generated tremendous interest because of their excellent biocompatibility, biodegradability, and mechanical strength. They are easy to formulate into various devices for carrying a variety of drug classes such as vaccines, peptides, proteins, and micromolecules. Most importantly, they have been approved by the United States Food and Drug Administration (FDA) for drug delivery. This review presents different preparation techniques of various drug-loaded PLGA devices, with special emphasis on preparing microparticles. Certain issues about other related biodegradable polyesters are discussed.

In vivo evaluation of zidovudine (AZT)-loaded ethylcellulose microspheres after oral administration in beagle dogs

The purpose of this study was to evaluate the in vivo performance of sustained-release zidovudine (AZT) microspheres after oral administration in Beagle dogs, and to establish an in vitro-in vivo correlation. Two AZT microsphere formulations as well as AZT powder were administered to four Beagle dogs. Plasma samples were analyzed by HPLC. The plasma concentration-time data was analyzed by both compartmental and noncompartmental pharmacokinetic analyses. Based on the calculated pharmacokinetic parameters, in vivo release profiles were simulated and compared with in vitro release profiles in three different release media. Significantly longer mean residence time (MRT) was observed after administration of the sustained-release microspheres compared with AZT powder. Significantly lower maximum (Cmax) concentration values and longer times to Cmax (tmax) values were also observed. Formulation I showed the longest MRT (4.4 h). AZT plasma concentration was maintained above the minimum effective concentration for approximately 10 h after administration of Formulation I. The relative bioavailability of the microsphere formulations with respect to AZT powder was not significantly different from 1. The in vitro release of the three formulations was slower in simulated gastric fluid compared with simulated intestinal fluid. The addition of enzymes and mucin to the release media significantly lowered the in vitro release rate of AZT from the microspheres formulations, but not from AZT powder. A good level of in vitro-in vivo correlation (Level A correlation) was achieved with a release medium that was composed of simulated gastric fluid with pepsin and mucin for 2 h followed by simulated intestinal fluid with pancreatin and mucin for 8 h. This in vitro model may be used to predict the in vivo release of AZT, in the further development of controlled-release AZT formulations.