Rifampicin-carrying poly(D,L-lactide) microspheres: loading and release

Formulation, Characterisation, and Biocompatibility Assessment of Rifampicin-Loaded Poly(d,l-lactide-co-glycolide) Composites for Local Treatment of Orthopaedic and Wound Infections

Background/Objectives: The escalating challenge of antimicrobial resistance (AMR) necessitates the development of targeted antibiotic delivery platforms, minimising systemic administration. Polymer-based drug delivery emerges as a promising solution, ensuring sustained release and prolonged efficacy of bioactive compounds, ensuring long-term efficacy. Methods: This study focuses on encapsulating rifampicin (RIF), a key antibiotic for orthopaedic and wound-related infections, within Poly(d,l-lactide-co-glycolide) (PLGA), a biodegradable polymer, through solvent casting, to formulate a PLGA-RIF composite membrane. Comprehensive characterisation, employing Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis and X-ray Diffraction (XRD), confirmed the integrity of both the starting and produced materials. UV-Vis spectroscopy revealed a controlled drug release profile over 21 days in various media, with the chosen media influencing the drug release, notably the tryptic soya broth (TSB) caused the highest release. The quantitative assessment of the antimicrobial efficacy of the developed PLGA-RIF composite was conducted by measuring the size of the inhibition zones against both Gram-negative and Gram-positive bacteria. Results: The results confirmed the composite's potential as a robust antibacterial biomaterial, demonstrating a rapid and effective antibacterial response. Cytocompatibility tests incorporated human fibroblast and osteoblast-like cell lines and demonstrated that the RIF:PLGA (1:8) formulation maintained eukaryotic cell viability, indicating the composite's potential for targeted medical applications in combating bacterial infections with minimal systemic impact. Conclusions: This study presents the significance of investigating drug release within appropriate and relevant physiological media. A key novelty of this work therefore lies in the exploration of drug release dynamics across different media, allowing for a comprehensive understanding of how varying physiological conditions may influence drug release and its effect on biological responses.

Nanosized Drug Delivery Systems to Fight Tuberculosis

Tuberculosis (TB) is currently the second deadliest infectious disease. Existing antitubercular therapies are long, complex, and have severe side effects that result in low patient compliance. In this context, nanosized drug delivery systems (DDSs) have the potential to optimize the treatment's efficiency while reducing its toxicity. Hundreds of publications illustrate the growing interest in this field. In this review, the main challenges related to the use of drug nanocarriers to fight TB are overviewed. Relevant publications regarding DDSs for the treatment of TB are classified according to the encapsulated drugs, from first-line to second-line drugs. The physicochemical and biological properties of the investigated formulations are listed. DDSs could simultaneously (i) optimize the therapy's antibacterial effects; (ii) reduce the doses; (iii) reduce the posology; (iv) diminish the toxicity; and as a global result, (v) mitigate the emergence of resistant strains. Moreover, we highlight that host-directed therapy using nanoparticles (NPs) is a recent promising trend. Although the research on nanosized DDSs for TB treatment is expanding, clinical applications have yet to be developed. Most studies are only dedicated to the development of new formulations, without the in vivo proof of concept. In the near future, it is expected that NPs prepared by "green" scalable methods, with intrinsic antibacterial properties and capable of co-encapsulating synergistic drugs, may find applications to fight TB.

Embolization with Polyhydroxybutyrate (PHB) Microspheres: In-Vivo Studies

In this study polyhydroxybutyrate (PHB), produced by a methanol-utilizing bacteria, was used to prepare microspheres in the 120-200 μm size range for embolization. A solvent evaporation technique was utilized to obtain microspheres in which methylene chloride, distilled water and polyvinyl alcohol were used as the solvent, precipitation medium and emulsifier, respectively. Dogs were the test animals. Renal angiograms obtained before and after embolization and also the histopathological observations showed the feasibility of using these microspheres as an alternative embolization/chemoembolization agent.

Cellular cytotoxicity and in-vivo biodistribution of docetaxel poly(lactide-co-glycolide) nanoparticles

Docetaxel (DTX) is one of the most effective antineoplastic drugs. However, its current clinical administration, formulated in tween80, causes serious side effects. This study is focused on preparation and evaluation of poly(lactide-co-glycolide) nanoparticles (NPs) containing DTX to remove tween80. Drug encapsulation efficiency, in-vitro drug release, cellular cytotoxicity, and in-vivo biodistribution of NPs in mice after intravenous administration were investigated. The average diameter of the NPs was approximately 172-178 nm with encapsulation efficiency of 68%. A burst release of approximately 30% (w/w) of the loaded drug followed by a sustained release profile was observed. Cellular mortality of the NPs was more than or at least as great as DTX free drug; for example, cell viability measured at 100 nmol/l drug concentration was decreased from 50.9% for DTX free drug to 15.9% for the NP formulation after 48 h incubation with T47D cells. The DTX plasma amount remained at a good level (13% of the initial dose) in the NP formulation compared with the DTX conventional formulation, which is approximately 0.5% of the initial dose, was present in plasma up to 2 h. Poly(lactide-co-glycolide) NPs containing DTX prepared in this study may be regarded as a suitable and superior formulation for the current formulation in the market containing tween80 with improved cancerous cell mortality and biodistribution characteristics.

Preparation of pegylated nano-liposomal formulation containing SN-38: In vitro characterization and in vivo biodistribution in mice

7-Ethyl-10-hydroxy-camptothecin (SN-38), a metabolite of irinotecan x HCl, is poorly soluble in aqueous solutions and practically insoluble in most physiologically compatible and pharmaceutically acceptable solvents. Formulation of SN-38 in concentrated pharmaceutical delivery systems for parenteral administration is thus very difficult. Due to their biocompatibility and low toxicity, liposomes were considered for the delivery of SN-38. In this study, pegylated liposomes with distearoylphosphatidylcholine, distearoylphosphatidylethanolamine containing SN-38 were prepared and their characteristics, such as particle size, encapsulation efficiency, in vitro drug release and biodistribution, were investigated. The particle size of liposomes was in the range of 150--200 nm. The encapsulation efficiency and in vitro release rate of pegylated liposomes was higher than those of non-pegylated liposomes. As expected, the distribution of pegylated liposomes in body organs such as liver, kidney, spleen and lung was considerably lower than that of non-pegylated liposomes. Also, their blood concentration was at least 50 % higher than that of non-pegylated liposomes.

Folate-receptor-targeted delivery of docetaxel nanoparticles prepared by PLGA-PEG-folate conjugate

For folate-receptor-targeted anticancer therapy, docetaxel (DTX) nanoparticles (NPs) were produced employing polylactide-co-glycolide-polyethylene glycol-folate (PLGA-PEG-FOL) conjugate. The FOL-conjugated di-block copolymer was synthesized by coupling the PLGA-PEG-NH(2) di-block copolymer with an activated folic acid. It was expected that FOL moieties were exposed on the micellar surface. The conjugates assisted in the formation of DTX NPs with an average size of 200 nm in diameter through an emulsification/solvent diffusion method. The FOL-targeted NPs showed a greater extent of intracellular uptake in FOL-receptor-positive cancer cells (SKOV3) in comparison with the non-targeted NPs, indicating that the FOL-receptor-mediated endocytosis mechanism could have a role in the cellular uptake of NPs. These results suggested that FOL-targeted DTX NPs could be a potentially useful delivery system for FOL-receptor-positive cancer cells.

Preparation and Characterization of Triamcinolone Acetonide-loaded Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) Microspheres

Triamcinolone acetonide loaded in poly(3-hydroxybutyrate-co-3 hydroxyhexanoate) (PHBHx) microspheres were prepared to treat cystoid macular oedema (CMO) and acute posterior segment inflammation associated with uveitis. The PHBHx microspheres were prepared by solvent evaporation technique using methylene chloride as the solvent and aqueous poly(vinyl alcohol) emulsifier as the dispersion medium. The PHBHx microspheres obtained were well formed with narrow size distribution; the average size prepared ranged from 40—200 μm depending on the formulation used. The stirring rate of the dispersion medium, emulsifier concentration, and polymer/solvent ratio parameters were varied to determine their effect on the size and size distribution of the PHBHx microspheres. Increasing the stirring rate and emulsifier concentration decreased the size and the size distribution of the microspheres, while increasing the polymer/solvent ratio caused the opposite effect. The polymer/drug ratio was the most effective parameter for controlling drug loading and release properties. More than 90% of the loaded drug was released within the first 24 h; after that, the release rate was slower for all formulations.

Preparation and antibacterial activity evaluation of rifampicin-loaded poly lactide-co-glycolide nanoparticles

Biodegradable polymers such as poly lactide-co-glycolides (PLGA) have been considered for the preparation of nanoparticles (NPs). In this study, rifampicin (RIF)-loaded PLGA NPs were fabricated by an emulsification/solvent diffusion method. The effect of several variables on the NPs' characteristics were evaluated, including the amount of RIF, amount of the poly vinyl alcohol as surfactant, and internal-phase volume and composition. The RIF encapsulation efficacy and the particle size distribution were optimized by varying these parameters. NPs were spherical with a relatively monodispersed size distribution. The effect of nanoencapsulation of RIF on the antibacterial activity of RIF against gram-positive and gram-negative bacteria was evaluated. It was shown that RIF NPs could considerably improve the RIF antibacterial efficacy.

Tuberculosis chemotherapy: current drug delivery approaches

Tuberculosis is a leading killer of young adults worldwide and the global scourge of multi-drug resistant tuberculosis is reaching epidemic proportions. It is endemic in most developing countries and resurgent in developed and developing countries with high rates of human immunodeficiency virus infection. This article reviews the current situation in terms of drug delivery approaches for tuberculosis chemotherapy. A number of novel implant-, microparticulate-, and various other carrier-based drug delivery systems incorporating the principal anti-tuberculosis agents have been fabricated that either target the site of tuberculosis infection or reduce the dosing frequency with the aim of improving patient outcomes. These developments in drug delivery represent attractive options with significant merit, however, there is a requisite to manufacture an oral system, which directly addresses issues of unacceptable rifampicin bioavailability in fixed-dose combinations. This is fostered by the need to deliver medications to patients more efficiently and with fewer side effects, especially in developing countries. The fabrication of a polymeric once-daily oral multiparticulate fixed-dose combination of the principal anti-tuberculosis drugs, which attains segregated delivery of rifampicin and isoniazid for improved rifampicin bioavailability, could be a step in the right direction in addressing issues of treatment failure due to patient non-compliance.

Studies on rifampicin release from ethylcellulose coated nonpareil beads

The rifampicin release studies from ethylcellulose coated nonpareil beads were studied. Propylene glycol and Castor oil were used as plasticizers. The in vitro dissolution studies revealed that the release rate is inversely proportional to percent of coating thickness. The release rate also depends on the type of plasticizer used in the coating polymer. The mechanism of drug release follows Higuchi diffusion model. Water vapour permeation studies indicated that the water vapour transport rate through free films is directly related to the drug release rate. DSC thermograms and IR spectras revealed that there is no interaction between rifampicin and other additives. SEM photographs of coated beads, before dissolution and after dissolution, also indicates that the drug release mechanism follows diffusion model.

Correlation of "in vitro" release and "in vivo" absorption characteristics of rifampicin from ethylcellulose coated nonpareil beads

The purpose of this study was to investigate the possibility to develop different levels of correlation between in vitro dissolution parameters and in vivo pharmacokinetic parameters for three rifampicin formulations. A level A correlation of in vitro release and in vivo absorption could be obtained for individual plasma level data by means of the Wagner and Nelson method. Linear correlation could be obtained when percent dose released in vitro was plotted vs percent dose absorbed in vivo with correlation coefficients between 0.954,0.983 and 0.997 for the formulations studied. A second level correlation between mean in vitro dissolution time (MDT) and mean in vivo residence time (MRT) was performed with a correlation coefficient of 0.536,0.420 and 0.335. Finally, it was also possible to establish a good in vitro-in vivo correlation when the T(50%hrs) (time taken to release 50% of rifampicin) in vitro and C(max),T(max) or AUC in vivo were compared.

Effect of chloroquine on phagolysosomal fusion in cultured guinea pig alveolar macrophages: implications in drug delivery

The aim of this study was to evaluate the effects of chloroquine on phagolysosomal fusion (PLF) in cultured guinea pig alveolar macrophages (AMs). This technique may be of significance for antitubercular drugs, because.the survival of Mycobacterium tuberculosis is linked to evasion of PLF. Guinea pig AMs were obtained from anesthetized animals after exsanguination. The AMs were cultured at a density of 1 x 10(6) cell/mL in 24-well plates after attachment to 13-mm coverslips. Culture conditions were at 37 degrees C, with 95% air/5% CO2 in Roswell Park Memorial Institute (RPMI) 1640 medium with 10% heat-inactivated fetal bovine serum. Rhodamine-dextran (70 kd) was incubated with the cells at 0.25 mg/mL for 24 hours to label the lysosomes. Chloroquine treatment where indicated was performed at 10-20 microg/mL for 1 hour. Fluorescent BioParticles were then added, and PLF was monitored by formation of an orange-yellow fluorescence on fusion of green fluorescent BioParticles with rhodamine-labeled lysosomes. PLF endpoints were measured by scoring for the percentage of orange-yellow cells in the field of view. Image analysis to measure the intensity of the orange-yellow color was performed by obtaining a, b values for 5 x 5 pixel areas using the PhotoAdobe program 4.0.1. The results indicated that the rate of PLF was enhanced by chloroquine. Thus, chloroquine may be used to potentiate the effects of rifampicin. This may be confirmed by studies involving similar dual fluorophore labeling techniques of fluorescein-labeled formulation in macrophages infected with M.tuberculosis. Preliminary studies with the rhodamine-labeled formulation confirmed cellular uptake and persistence for up to 7 days in culture.

Preparation and in vitro evaluation of chitosan matrices cross-linked by formaldehyde vapors

Rifampicin-chitosan matrices were prepared by a chemical cross-linking method to develop a sustained-release form. The effects of cross-linking agent (formaldehyde) on the drug release rate and release kinetics were investigated in this study. Moreover, the kinetics of rifampicin released from chitosan matrices exposed to formaldehyde vapors for predetermined time intervals were analyzed using Ritger and Peppas exponential equation. The in vitro release kinetics exhibited a non-Fickian transport model. Increasing the exposure time to formaldehyde vapors decreased the release rate of rifampicin from chitosan matrices as a result of formation of greater structural strength and tighter texture.

Respirable PLGA microspheres containing rifampicin for the treatment of tuberculosis: manufacture and characterization

PURPOSE

Particles with aerodynamic diameters of 1-5 microm deposit in the periphery of the lungs and are phagocytized by alveolar macrophages, the primary site of Mycobacterium tuberculosis infection. Aerosols of biodegradable polymeric microspheres containing antitubercular agents may be delivered to the lungs to improve the treatment of tuberculosis.

METHODS

Poly(lactide-co-glycolide) (PLGA) microspheres containing rifampicin were prepared using solvent evaporation and spray drying methods. The solvent evaporation process was optimized using factorial experimental design and surface response methodology. The morphology, particle size, drug loading, and dissolution of microspheres was evaluated.

RESULTS

The spray dried rifampicin loaded PLGA microparticles were shriveled, unlike the spherical particles produced by solvent evaporation. Drug loadings of 20% and 30% were achieved for solvent evaporation and spray dried products, respectively. The particles prepared by solvent evaporation and spray drying had 3.45 microm and 2.76 microm median diameters by volume, respectively.

CONCLUSIONS

Respirable rifampicin loaded PLGA microspheres were produced by both solvent evaporation and spray drying methods. These particles are being evaluated in an animal model of tuberculosis.

Rifampicin carrying polyhydroxybutyrate microspheres as a potential chemoembolization agent

In this study, we attempted to prepare microspheres from a microbial biodegradable polyester, i.e. polyhydroxybutyrate (PHB) as a potential chemoembolization agent. The drug loaded PHB microspheres were prepared by a solvent evaporation technique, in which methylene chloride, distilled water, and polyvinyl alcohol were utilized as the solvent, dispersion medium, and emulsifier, respectively. Microspheres were obtained within a size range of 5-100 microns by changing the initial polymer/solvent ratio, emulsifier concentration, stirring rate, and initial drug concentration. It was possible to obtain PHB with very narrow size distributions by applying gravity field-flow fractionation technique. Very high drug loadings of up to 407.6 mg rifampicin/g PHB were achieved. Drug release rates were very rapid. Almost 90% of the drug loaded was released in about 24 h. Both the size and drug content of PHB microspheres were found to be effective in controlling the drug release from these microspheres.

Rifampicin carrying poly (D,L-lactide)/poly(ethylene glycol) microspheres: loading and release

The aim of this study is to prepare rifampicin-loaded poly (D,L-lactide)/poly(ethylene golycol) (PDLLA/ PEG) copolymer microspheres as an injectable drug delivery system. PDLLA homopolymers with three different molecular weights (9,760, 14,540, and 23,050 daltons) were synthesized and then transesterified with PEG (with a molecular weight of approximately 3,300-4,000 daltons). By changing the ratio of PEG to PDLLA, block copolymers with different chain structures were synthesized. PDLLA and PDLLA/PEG microspheres in the size range of 2-10 microns were prepared by a modified solvent evaporation technique with the use of methylene chloride as the solvent and methyl cellulose as the emulsifier within the aqueous dispersion medium. Rifampicin was loaded within the microspheres during particle formation. Effects of the solvent/polymer and drug/polymer ratios, PDLLA molecular weight, and PEG content on drug loading and release were investigated. High drug loadings up to 100 mg rifampicin/g polymer were achieved. Both size and drug loadings were decreased by an increase in the solvent/polymer ratio and PEG content and by a decrease in the drug/polymer ratio and PDLLA molecular weight. High release rates were observed in the first 5 days after which constant and slow release rates were noted. Drug release was decreased by a decrease in the solvent/polymer ratio and PEG content and by an increase in the drug/polymer ratio and PDLLA molecular weight.

A potential soft tissue filling material: chloramphenicol loaded poly(D,L-lactide) sponges

Poly(D,L-lactide) (PDLLA) homopolymers were produced by the ring opening polymerization of a D,L-lactide dimer by using stannous chloride as the catalyst. Chloramphenicol loaded PDLLA sponges were pre- pared by a solvent evaporation procedure by using the PDLLA homopolymers with three different molecular weights (i.e., 11,000, 20,000 and 35,000 daltons). Chloramphenicol loading was changed by using three different solvents (i.e., acetone, ethyl acetate, and acetonitrile) and by changing the initial polymer concentration and its molecular weight and the initial concentration of the drug. Higher degradation rates of the chloramphenicol loaded PDLLA sponges in alkaline pH 9.0 and at 37 degrees C were observed. Chloramphenicol release rates were also high at these conditions. It was concluded that chloramphenicol release was both degradation and diffusion controlled.