Chemotherapy of Mycobacterium tuberculosis infections in mice with a combination of isoniazid and rifampicin entrapped in Poly (DL-lactide-co-glycolide) microparticles

A Current Perspective on the Potential of Nanomedicine for Anti-Tuberculosis Therapy

Tuberculosis (TB) is one of the ten infectious diseases that cause the highest amount of human mortality and morbidity. This infection, which is caused by a single pathogen, Mycobacterium tuberculosis, kills over a million people every year. There is an emerging problem of antimicrobial resistance in TB that needs urgent treatment and management. Tuberculosis treatment is complicated by its complex drug regimen, its lengthy duration and the serious side-effects caused by the drugs required. There are a number of critical issues around drug delivery and subsequent intracellular bacterial clearance. Drugs have a short lifespan in systemic circulation, which limits their activity. Nanomedicine in TB is an emerging research area which offers the potential of effective drug delivery using nanoparticles and a reduction in drug doses and side-effects to improve patient compliance with the treatment and enhance their recovery. Here, we provide a minireview of anti-TB treatment, research progress on nanomedicine and the prospects for future applications in developing innovative therapies.

Mimicking chronic glaucoma over 6 months with a single intracameral injection of dexamethasone/fibronectin-loaded PLGA microspheres

To create a chronic glaucoma animal model by a single intracameral injection of biodegradable poly lactic-co-glycolic acid (PLGA) microspheres (Ms) co-loaded with dexamethasone and fibronectin (MsDexaFibro). MsDexaFibro were prepared by a water-in-oil-in-water emulsion method including dexamethasone in the organic phase and fibronectin in the inner aqueous phase. To create the chronic glaucoma model, an interventionist and longitudinal animal study was performed using forty-five Long Evans rats (4-week-old). Rats received a single intracameral injection of MsDexafibro suspension (10%w/v) in the right eye. Ophthalmological parameters such as clinical signs, intraocular pressure (IOP), neuro-retinal functionality by electroretinography (ERG), retinal structural analysis by optical coherence tomography (OCT), and histology were evaluated up to six months. According to the results obtained, the model proposed was able to induce IOP increasing in both eyes over the study, higher in the injected eyes up to 6 weeks (p < 0.05), while preserving the ocular surface. OCT quantified progressive neuro-retinal degeneration (mainly in the retinal nerve fiber layer) in both eyes but higher in the injected eye. Ganglion cell functionality decreased in injected eyes, thus smaller amplitudes in PhNR were detected by ERG. In conclusion, a new chronic glaucoma animal model was created by a single injection of MsDexaFibro very similar to open-angle glaucoma occurring in humans. This model would impact in different fields such as ophthalmology, allowing long period of study of this pathology; pharmacology, evaluating the neuroprotective activity of active compounds; and pharmaceutical technology, allowing the correct evaluation of the efficacy of long-term sustained ocular drug delivery systems.

In silico identification and synthesis of a multi-drug loaded MOF for treating tuberculosis

Conventional drug delivery systems have been applied to a myriad of active ingredients but may be difficult to tailor for a given drug. Herein, we put forth a new strategy, which designs and selects the drug delivery material by considering the properties of encapsulated drugs (even multiple drugs, simultaneously). Specifically, through an in-silico screening process of 5109 MOFs using grand canonical Monte Carlo simulations, a customized MOF (referred as BIO-MOF-100) was selected and experimentally verified to be biologically stable, and capable of loading 3 anti-Tuberculosis drugs Rifampicin+Isoniazid+Pyrazinamide at 10% + 28% + 23% wt/wt (total > 50% by weight). Notably, the customized BIO-MOF-100 delivery system cleared naturally Pyrazinamide-resistant Bacillus Calmette-Guérin, reduced growth of virulent Erdman infection in macaque macrophages 10-100-fold compared to soluble drugs in vitro and was also significantly reduced Erdman growth in mice. These data suggest that the methodology of identifying-synthesizing materials can be used to generate solutions for challenging applications such as simultaneous delivery of multiple, small hydrophilic and hydrophobic molecules in the same molecular framework.

Dual antitubercular drug loaded liposomes for macrophage targeting: development, characterisation, ex vivo and in vivo assessment

AIM

The present study was conducted to formulate and investigate liposomes for the dual drug delivery based on anti-tubercular drug(s) combination i.e. Isoniazid (INH) and Rifampicin (RIF).

MATERIALS AND METHODS

Mannosylated and non mannosylated liposomes were prepared by lipid thin film hydration method, using DSPC: Chol at a molar ratio 6:4 while in case of mannosylated liposomes DSPC: Chol: Man-C4-Chol at a molar ratio 6.0:3.5:0.5 were used and extensively characterised. The particle size and zeta potential were recorded to be 1.29 ± 0.24 µm and -9.1 ± 0.11 mV. The drug entrapment (%) was recorded to be 84.7 ± 1.25% for Rifampicin and 31.8 ± 0.12% for Isoniazid.

RESULTS

The antitubercular activity studied in Balb/C mice was maximum in the case of mannosylated liposomes. The biodistribution studies also revealed higher drug(s) concentration (accumulation) maintained over a protracted period.

CONCLUSIONS

The liposomal preparations are passively as well as actively uptaken by the alveolar macrophages which are the cellular tropics of infection. The mannosylated liposomes appear to be a potential carrier for dual drug delivery and targeted antitubercular therapy.

Gentamicin-Loaded Chitosan Nanoparticles Improve Its Therapeutic Effects on Brucella-Infected J774A.1 Murine Cells

BACKGROUND

Final elimination of some intracellular bacterial agents, such as Brucella, is often a complex issue and impossible to achieve, primarily due to the presence and survival of the bacteria within phagocytic cells. By penetrating into the cell membrane, drug delivery nanosystems can reduce the number of intracellular bacteria. The aim of this study was to assess the efficacy of chitosan nanoparticles on the delivery of gentamicin into Brucella infected J774A.1 murine cells in vitro.

MATERIALS AND METHODS

Chitosan nanoparticles (NPs) were synthesized using ionic gelation technique. The shape, size and charge of NPs, loading rate and release of the drug were investigated. Finally, the effects of gentamicin-loaded chitosan NPs (Gen-Cs) and free gentamicin on J774A.1 murine cells infected with these bacteria were examined.

RESULTS

The mean size and charge of NPs were computed as 100 nm and +28mV, respectively. The loading capacity of NPs was 22%. About 70% of the drug was released from NPs during the first 8 hours. Antimicrobial activity of the two formulations showed that MIC (minimum inhibitory concentration) of the Gen-Cs and free drug was 3.1 and 6.25 µg, respectively. The minimum bactericidal concentration of the NPs-loaded drug and free drug was 6.25 and 12.5 µg, respectively. Cell culture analysis revealed that there was a significant reduction in the load of the intercellular bacteria in J774A.1 murine cells in both formulations.

CONCLUSION

Our results showed the Gen-Cs have a proper potential for optimal treatment of intracellular bacterial agents.

Synthesis and Characterization of pH-Sensitive Inulin Conjugate of Isoniazid for Monocyte-Targeted Delivery

The use of particles for monocyte-mediated delivery could be a more efficient strategy and approach to achieve intracellular targeting and delivery of antitubercular drugs to host macrophages. In this study, the potential of inulin microparticles to serve as a drug vehicle in the treatment of chronic tuberculosis using a monocytes-mediated drug targeting approach was evaluated. Isoniazid (INH) was conjugated to inulin via hydrazone linkage in order to obtain a pH-sensitive inulin-INH conjugate. The conjugate was then characterized using proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FTIR) as well as in vitro, cellular uptake and intracellular Mycobacterium tuberculosis (Mtb) antibacterial efficacy. The acid-labile hydrazone linkage conferred pH sensitivity to the inulin-INH conjugate with ~95, 77 and 65% of the drug released after 5 h at pH 4.5, 5.2, and 6.0 respectively. Cellular uptake studies confirm that RAW 264.7 monocytic cells efficiently internalized the inulin conjugates into endocytic compartments through endocytosis. The intracellular efficacy studies demonstrate that the inulin conjugates possess a dose-dependent targeting effect against Mtb-infected monocytes. This was through efficient internalization and cleavage of the hydrazone bond by the acidic environment of the lysosome, which subsequently released the isoniazid intracellularly to the Mtb reservoir. These results clearly suggest that inulin conjugates can serve as a pH-sensitive intracellular drug delivery system for TB treatment.

Carbon nanomaterials: a new way against tuberculosis

Introduction: Tuberculosis (TB) remains one of the most alarming worldwide infectious diseases primarily in low-income countries, where the infection shows a higher and unvaried prevalence. In the last years, the emergence and spread of Mycobacterium tuberculosis (Mtb) strains resistant to first-line anti-TB drugs are the cause of major concern and prompted the implementation of new treatments, including the development of new drugs and the repurposing of old ones. Areas covered: In this review, we discuss solutions against TB based on nanomaterials (NMTs), alone or combined with current anti-TB drugs. We will summarize drug delivery platforms tested in in vivo or in vitro models and their activity against mycobacteria. We will describe how the new nanotechnologies based on carbon nanomaterials, like carbon nanotubes and graphene oxide are now facing the panorama of the medical fight against TB. Expert opinion: We foresee that in the next decade carbon nanomaterials will be at the forefront in fighting emerging antibiotic-resistant Mtb strains by shortening treatment periods, reducing adverse effects and mitigating antibiotic use. However, toxicity and biodegradation studies should be done prior to the clinical translation of carbon nanomaterials.

Selective drug deposition in lungs through pulmonary drug delivery system for effective management of drug-resistant TB

INTRODUCTION

The emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) is a major health issue and continues to be a global health concern. Despite significant advancements in treatment modalities, ~1.6 million deaths worldwide occur due to TB infection. This is because of tuberculosis reservoirs in the alveoli making it a challenge for the formulation scientist to target this.

AREAS COVERED

This review recent investigations on the forefront of pulmonary drug delivery for managing MDR-TB and XDR-TB. Novel delivery systems like liposomes, niosomes, employing carbohydrate, and -coated molecules via conjugation to selectively deliver the drugs to the lung TB reservoir via pulmonary administration are discussed.

EXPERT OPINION

Poor patient adherence to treatment due to side effects and extended therapeutic regimen leads to drug-resistant TB. Thus, it is essential to design novel strategies this issue by developing new chemical entities and/or new delivery systems for delivery to the lungs, consequently reducing the side effects, the frequency and the duration of treatment. Delivery of drugs to enhance the efficacy of new/existing anti-TB drugs to overcome the resistance and enhance patient compliance is underway.

Glucosamine/L-lactide copolymers as potential carriers for the development of a sustained rifampicin release system using Mycobacterium smegmatis as a tuberculosis model

The present study aims at developing a new, ultrafine particle-based efficient antibiotic delivery system for the treatment of tuberculosis. The carrier material to make the rifampicin (RIF)-loaded particles is a low molecular weight star-shaped polymer produced from glucosamine (core building unit) and L-lactide (GluN-LLA). Particles were made via electrohydrodynamic atomization. Prolonged release (for up to 14 days) of RIF from these particles is reported. Drug release data fits the Korsmeyer-Peppas equation, which suggests the occurrence of a modified diffusion-controlled RIF release mechanism in vitro and is also supported by differential scanning calorimetry and drug leaching tests. Cytotoxicity tests on Mycobacterium smegmatis showed that antibiotic-free GluN-LLA and polylactides (PLA) particles (reference materials) did not show any significant anti-bacterial activity. The minimum inhibitory concentration and minimum bactericidal concentration values obtained for RIF-loaded particles showed 2- to 4-fold improvements in the anti-bacterial activity relative to the free drug. Cytotoxicity tests on macrophages indicated that cell death correlates with an increase of particle concentration but is not significantly affected by material type or particle size. Confocal microscopy was used to track internalization and localization of particles in the macrophages. The uptake of GluN-LLA particles is higher than those of their PLA counterparts. In addition, after phagocytosis, the GluN-LLA particles stayed in the cytoplasm and showed favorable long-term drug release behavior, which facilitated the killing of intracellular bacteria when compared to free RIF. The present studies suggest that these drug carrier materials are potentially very attractive candidates for the development of high-payload, sustained-release antibiotic/resorbable polymer particle systems for treating bacterial lung infections.

Long-acting formulations for the treatment of latent tuberculous infection: opportunities and challenges

Long-acting/extended-release drug formulations have proved very successful in diverse areas of medicine, including contraception, psychiatry and, most recently, human immunodeficiency virus (HIV) disease. Though challenging, application of this technology to anti-tuberculosis treatment could have substantial impact. The duration of treatment required for all forms of tuberculosis (TB) put existing regimens at risk of failure because of early discontinuations and treatment loss to follow-up. Long-acting injections, for example, administered every month, could improve patient adherence and treatment outcomes. We review the state of the science for potential long-acting formulations of existing tuberculosis drugs, and propose a target product profile for new formulations to treat latent tuberculous infection (LTBI). The physicochemical properties of some anti-tuberculosis drugs make them unsuitable for long-acting formulation, but there are promising candidates that have been identified through modeling and simulation, as well as other novel agents and formulations in preclinical testing. An efficacious long-acting treatment for LTBI, particularly for those co-infected with HIV, and if coupled with a biomarker to target those at highest risk for disease progression, would be an important tool to accelerate progress towards TB elimination.

Nanomedicines as Drug Delivery Carriers of Anti-Tubercular Drugs: From Pathogenesis to Infection Control

In spite of advances in tuberculosis (TB) chemotherapy, TB is still airborne deadly disorder as a major issue of health concern worldwide today. Extensive researches have been focused to develop novel drug delivery systems to shorten the lengthy therapy approaches, prevention of relapses, reducing dose-related toxicities and to rectify technologically related drawbacks of anti-tubercular drugs. Moreover, the rapid emergence of drug resistance, poor patient compliance due to negative therapeutic outcomes and intracellular survival of Mycobacterium highlighted to develop carrier with optimum effectiveness of the anti-tubercular drugs. This could be achieved by targeting and concentrating the drug on the infection reservoir of Mycobacterium. In this article, we briefly compiled the general aspects of Mycobacterium pathogenesis, disease treatment along with progressive updates in novel drug delivery carrier system to enhance therapeutic effects of drug and the high level of patient compliance. Recently developed several vaccines might be shortly available as reported by WHO.

Antimycobacterial susceptibility evaluation of rifampicin and isoniazid benz-hydrazone in biodegradable polymeric nanoparticles against Mycobacterium tuberculosis H37Rv strain

INTRODUCTION

Tuberculosis (TB) is the single largest infectious disease which requires a prolonged treatment regime with multiple drugs. The present treatment for TB includes frequent administration of a combination of four drugs for a duration of 6 months. This leads to patient's noncompliance, in addition to developing drug-resistant strains which makes treatment more difficult. The formulation of drugs with biodegradable polymeric nanoparticles (NPs) promises to overcome this problem.

MATERIALS AND METHODS

In this study, we focus on two important drugs used for TB treatment - rifampicin (RIF) and isoniazid (INH) - and report a detailed study of RIF-loaded poly lactic-co-glycolic acid (PLGA) NPs and INH modified as INH benz-hydrazone (IH2) which gives the same therapeutic effect as INH but is more stable and enhances the drug loading in PLGA NPs by 15-fold compared to INH. The optimized formulation was characterized using particle size analyzer, scanning electron microscopy and transmission electron microscopy. The drug release from NPs and stability of drug were tested in different pH conditions.

RESULTS

It was found that RIF and IH2 loaded in NPs release in a slow and sustained manner over a period of 1 month and they are more stable in NPs formulation compared to the free form. RIF- and IH2-loaded NPs were tested for antimicrobial susceptibility against Mycobacterium tuberculosis H37Rv strain. RIF loaded in PLGA NPs consistently inhibited the growth at 70% of the minimum inhibitory concentration (MIC) of pure RIF (MIC level 1 µg/mL), and pure IH2 and IH2-loaded NPs showed inhibition at MIC equivalent to the MIC of INH (0.1 µg/mL).

CONCLUSION

These results show that NP formulations will improve the efficacy of drug delivery for TB treatment.

Targeted delivery of rifampicin to tuberculosis-infected macrophages: design, in-vitro, and in-vivo performance of rifampicin-loaded poly(ester amide)s nanocarriers

We have developed a nano drug delivery system for the treatment of tuberculosis (TB) using rifampicin (RF) encapsulated in poly(ester amide)s nanoparticles (PEA-RF-NPs), which are biocompatible polymers. In this study, biodegradable amino acid based poly(ester amide)s (PEAs) were synthesized by the poly condensation reaction and RF-loaded NPs were fabricated by the dialysis method. The surface morphology and in-vitro drug release efficiency were examined. The effect of time and temperature on the cellular uptake of PEA-RF-NPs in NR8383 cells was evaluated. Fluorescence microscopic results of PEA-RF-NPs from NR8383 cell lines suggest its potential application in treating TB. The antibacterial activity of RF against Mycobacterium smegmatis was also evaluated. Based on these results, this approach provides a new means for controlled and efficient release of RF using the PEA-NPs delivery system and is promising for the treatment of TB.

Targeted theranostic liposomes: rifampicin and ofloxacin loaded pegylated liposomes for theranostic application in mycobacterial infections

Theranostic liposomes as effective drug delivery systems for the management of infections.

Delivery of antibiotics with polymeric particles

Despite the wide use of antibiotics, bacterial infection is still one of the leading causes of hospitalization and mortality. The clinical failure of antibiotic therapy is linked with low bioavailability, poor penetration to bacterial infection sites, and the side effects of antibiotics, as well as the antibiotic resistance properties of bacteria. Antibiotics encapsulated in nanoparticles or microparticles made up of a biodegradable polymer have shown great potential in replacing the administration of antibiotics in their "free" form. Polymeric particles provide protection to antibiotics against environmental deactivation and alter antibiotic pharmacokinetics and biodistribution. Polymeric particles can overcome tissue and cellular barriers and deliver antibiotics into very dense tissues and inaccessible target cells. Polymeric particles can be modified to target or respond to particular tissues, cells, and even bacteria, and thereby facilitate the selective concentration or release of the antibiotic at infection sites, respectively. Thus, the delivery of antibiotics with polymeric particles augments the level of the bioactive drug at the site of infection while reducing the dosage and the dosing frequency. The end results are improved therapeutic effects as well as decreased "pill burden" and drug side effects in patients. The main objective of this review is to analyze recent advances and current perspectives in the use of polymeric antibiotic delivery systems in the treatment of bacterial infection.

Adjunctive immunotherapy with α-crystallin based DNA vaccination reduces Tuberculosis chemotherapy period in chronically infected mice

By employing modified Cornell model, we have evaluated the potential of adjunctive immunotherapy with DNA vaccines to shorten the tuberculosis chemotherapy period and reduce disease reactivation. We demonstrate that α-crystallin based DNA vaccine (DNAacr) significantly reduced the chemotherapy period from 12 weeks to 8 weeks when compared with the chemotherapy alone. Immunotherapy with SodA based DNA vaccine (DNAsod) reduced the pulmonary bacilli only as much as DNAvec. Both DNAacr and DNAsod, although significantly delayed the reactivation in comparison to the chemotherapy alone, this delay was associated with the immunostimulatory sequences present in the vector backbone and was not antigen specific. Both DNA vaccines resulted in the production of significantly higher number of T_EM cells than the chemotherapy alone, however, only in the case of DNAsod, this enhancement was significant over the DNAvec treatment. Overall, our findings emphasize the immunotherapeutic potential of DNAacr in shortening the duration of TB chemotherapy.

Stimuli responsive nanocarrier for an effective delivery of multi-frontline tuberculosis drugs

We prepare stimuli responsive polymeric nanocarrier, RCP-2 to demonstrate the high drug content as well as controlled release in a systematic manner.

In VitroStudies on the Release of Isoniazid Incorporated in Poly(ε-Caprolactone)

A polymeric micro- and nanosphere formulation using poly (epsilon-caprolactone) (PCL) to entrap an antituberculosis drug, isoniazid (INH), was developed and characterized. The microspheres were prepared by a solvent evaporation method using ethyl acetate, PCL and INH as the organic phase and water and Tween 40 as the aqueous phase. The nanospheres were prepared by a spontaneous emulsification solvent diffusion method using 40% ethanol in acetone (v/v), PCL and INH as the organic phase and water and Tween 40 as the aqueous phase. After freeze-drying, these systems were characterized by scanning electron microscopy (SEM), particle size analysis, determination of entrapped INH content, in vitro INH release and brine shrimp toxicity bioassay.

Fabrication and characterization of monodisperse PLGA-alginate core-shell microspheres with monodisperse size and homogeneous shells for controlled drug release

Monodisperse PLGA-alginate core-shell microspheres with controlled size and homogeneous shells were first fabricated using capillary microfluidic devices for the purpose of controlling drug release kinetics. Sizes of PLGA cores were readily controlled by the geometries of microfluidic devices and the fluid flow rates. PLGA microspheres with sizes ranging from 15 to 50μm were fabricated to investigate the influence of the core size on the release kinetics. Rifampicin was loaded into both monodisperse PLGA microspheres and PLGA-alginate core-shell microspheres as a model drug for the release kinetics studies. The in vitro release of rifampicin showed that the PLGA core of all sizes exhibited sigmoid release patterns, although smaller PLGA cores had a higher release rate and a shorter lag phase. The shell could modulate the drug release kinetics as a buffer layer and a near-zero-order release pattern was observed when the drug release rate of the PLGA core was high enough. The biocompatibility of PLGA-alginate core-shell microspheres was assessed by MTT assay on L929 mouse fibroblasts cell line and no obvious cytotoxicity was found. This technique provides a convenient method to control the drug release kinetics of the PLGA microsphere by delicately controlling the microstructures. The obtained monodisperse PLGA-alginate core-shell microspheres with monodisperse size and homogeneous shells could be a promising device for controlled drug release.

Drug delivery systems: An updated review

Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. For the treatment of human diseases, nasal and pulmonary routes of drug delivery are gaining increasing importance. These routes provide promising alternatives to parenteral drug delivery particularly for peptide and protein therapeutics. For this purpose, several drug delivery systems have been formulated and are being investigated for nasal and pulmonary delivery. These include liposomes, proliposomes, microspheres, gels, prodrugs, cyclodextrins, among others. Nanoparticles composed of biodegradable polymers show assurance in fulfilling the stringent requirements placed on these delivery systems, such as ability to be transferred into an aerosol, stability against forces generated during aerosolization, biocompatibility, targeting of specific sites or cell populations in the lung, release of the drug in a predetermined manner, and degradation within an acceptable period of time.

Antitubercular effect of 8-[(4-Chloro phenyl) sulfonyl]-7-Hydroxy-4-Methyl-2H-chromen-2-One in guinea pigs

OBJECTIVE

TO EVALUATE THE ANTITUBERCULAR EFFICACY AND SAFETY OF NEW CHEMICAL ENTITY (NCE): 8-[(4-Chloro phenyl) sulfonyl]-7-Hydroxy-4-Methyl-2H-chromen-2-One (CSHMC) in guinea pigs.

MATERIALS AND METHODS

This pilot study was carried out in guinea pigs. They were infected with M. tuberculosis H(37)Rv (1.5 × 10(4) cfu/guinea pig) via intramuscular route. After 30 days, infections were confirmed in 6 guinea pigs by histopathology of spleen, lung, and liver. After that CSHMC (5 and 20 mg/kg) was administered for 1 month and its effect was compared with vehicle, rifampicin (60 mg/kg) and isoniazid (30 mg/kg). Efficacy of CSHMC was evaluated on the basis of histopathologic scoring of lesion in lung, spleen, liver, and safety on the basis of measuring hemogram, liver and renal function parameters.

RESULTS

Isoniazid, rifampicin, and CSHMC (20 mg/kg) significantly reduce the median lesion score in lung, spleen, and liver as compared to disease control group. Reduction in median lesion score for lung and spleen were not statistically significant for CSHMC 5 mg/kg. CSHMC (20 and 5 mg/kg) did not produce any changes in hemogram, liver and renal function parameters with respect to normal values.

CONCLUSIONS

CSHMC had shown significant antitubercular efficacy comparable to isoniazid and rifampicin and did not show hematological, hepato- and nephrotoxicity.

Drug delivery systems for differential release in combination therapy

INTRODUCTION

Combination therapy with multiple therapeutic agents has wide applicability in medical and surgical treatment, especially in the treatment of cancer. Thus, new drug delivery systems that can differentially release two or more drugs are desired. Utilizing new techniques to engineer the established drug delivery systems and synthesizing new materials and designing carriers with new structures are feasible ways to fabricate proper multi-agent delivery systems, which are critical to meet requirements in the clinic and improve therapeutic efficacy.

AREAS COVERED

This paper aims to give an overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy. Multi-agent delivery systems from nanoscale to bulk scale, such as liposomes, micelles, polymer conjugates, nano/microparticles and hydrogels, developed over the last 10 years, have been collected and summarized. The characteristics of different delivery systems are described and discussed, including the structure of drug carriers, drug-loading techniques, release behaviors and consequent evaluation in biological assays.

EXPERT OPINION

The chemical structure of drug delivery systems is the key to controlling the release of therapeutic agents in combination therapy, and the differential release of multiple drugs could be realized by the successful design of a proper delivery system. Besides biological evaluation in vitro and in vivo, it is important to speed up practical application of the resulting delivery systems.

Fighting tuberculosis: old drugs, new formulations

This review reports the state of the art on innovative drug delivery strategies designed for antitubercular chemotherapeutics. The introduction contains the fundamental biological background concerning tuberculosis and a review of the current antitubercular therapy, and is followed by a critical report of the micrometric and nanometric particulate systems designed and investigated to improve tuberculosis chemotherapy.

Biodegradable polymeric nanocarriers for pulmonary drug delivery

BACKGROUND

Pulmonary drug delivery is attractive for both local and systemic drug delivery as a non-invasive route that provides a large surface area, thin epithelial barrier, high blood flow and the avoidance of first-pass metabolism.

OBJECTIVE

Nanoparticles can be designed to have several advantages for controlled and targeted drug delivery, including controlled deposition, sustained release, reduced dosing frequency, as well as an appropriate size for avoiding alveolar macrophage clearance or promoting transepithelial transport.

METHODS

This review focuses on the development and application of biodegradable polymers to nanocarrier-based strategies for the delivery of drugs, peptides, proteins, genes, siRNA and vaccines by the pulmonary route.

RESULTS/CONCLUSION

The selection of natural or synthetic materials is important in designing particles or nanoparticle clusters with the desired characteristics, such as biocompatibility, size, charge, drug release and polymer degradation rate.

Phagocytic activity of alveolar macrophages toward polystyrene latex microspheres and PLGA microspheres loaded with anti-tuberculosis agent

Phagocytosis of alveolar macrophages (Mphis) toward poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) loaded with the anti-tuberculosis agent rifampicin (RFP-PLGA MS) has been shown to be effective for the treatment of tuberculosis. The phagocytosis should be evaluated in terms of that toward reference MS. We chose polystyrene latex (PSL) MS as a reference. In this study, phagocytic activity of cell line NR8383, derived from rat alveolar Mphi, toward PSL MS with various diameters was examined by incubating the cells for 4h at 37 degrees C with various numbers of PSL MS per Mphi cell (MS/Mphi=0.1-10). The results were then compared with those of the phagocytosis toward RFP-PLGA MS. We determined the phagocytic activity by counting the population of Mphi cells that had phagocytosed MS (N) and the number of particles phagocytosed (n) in microscopic fields. Both N and n for PSL and RFP-PLGA MS increased in general with an increase in MS/Mphi, but both of these values for PSL MS were smaller than those for RFP-PLGA MS. Phagocytosis of the particles were dependent on the particle size; i.e., of the PSL MS the 6-mum ones were taken up by Mphi the most, and the RFP-PLGA MS 3 microm in diameter seemed to be phagocytosed the most efficiently, although we were not able to determine exactly the phagocytosis of 6- and 10-microm RFP-PLGA MS. From the changes in N and n values with MS/Mphi, the phagocytosis of RFP-PLGA MS was likely to enhance the phagocytic activity of Mphi cells, but this effect did not seem to be significant for PSL MS.

Quantification of isoniazid and acetylisoniazid in rat plasma and alveolar macrophages by liquid chromatography-tandem mass spectrometry with on-line extraction

To evaluate if pulmonary delivery of microparticles loaded with a prodrug of isoniazid (INH), isoniazid methanesulfonate (INHMS), can target alveolar macrophages (AM) and reduce metabolism of INH, an HPLC-MS/MS assay with automated online extraction for quantification of INH and its metabolite acetylisoniazid (AcINH) in plasma and AMs was developed and validated. Reproducibility in rat plasma and homogenate of a rat AM cell line, NR8383, for INH and AcINH showed excellent precision and accuracy with calibration curves exhibiting linearity within a range of 1-250ng/ml of INH and 0.05-50ng/ml of AcINH (r(2)>0.99). The validated methods were successfully applied to pharmacokinetic study of INHMS-loaded microparticles in rats, demonstrating efficient targeting of AMs and reduction of INH metabolism.

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.

Dendrimeric micelles for controlled drug release and targeted delivery

This review highlights the developments in dendrimer-based micelles for drug delivery. Dendrimers, the perfectly branched monodisperse macromolecules, have certain structural advantages that make them attractive candidates as drug carriers for controlled release or targeted delivery. As polymeric micelle-based approaches precede the work in dendrimers, these are also discussed briefly. The review concludes with a perspective on possible applications of biaryl-based dendrimeric micelles that exhibit environment-dependent conformations, in drug delivery.

The potential advantages of nanoparticle drug delivery systems in chemotherapy of tuberculosis

Nanoparticle-based drug delivery systems have considerable potential for treatment of tuberculosis (TB). The important technological advantages of nanoparticles used as drug carriers are high stability, high carrier capacity, feasibility of incorporation of both hydrophilic and hydrophobic substances, and feasibility of variable routes of administration, including oral application and inhalation. Nanoparticles can also be designed to allow controlled (sustained) drug release from the matrix. These properties of nanoparticles enable improvement of drug bioavailability and reduction of the dosing frequency, and may resolve the problem of nonadherence to prescribed therapy, which is one of the major obstacles in the control of TB epidemics. This article highlights some of the issues of nanotechnology relevant to the anti-TB drugs.

Chemotherapeutic efficacy of poly (DL-lactide-co-glycolide) nanoparticle encapsulated antitubercular drugs at sub-therapeutic dose against experimental tuberculosis

The present study was designed to evaluate the chemotherapeutic efficacy of poly (DL-lactide-co-glycolide) (PLG) nanoparticles (NP) encapsulating three front-line antitubercular drugs (ATDs: rifampicin, RIF; isoniazid, INH and pyrazinamide, PZA) at 2/3rd therapeutic dose. PLG nanoparticles prepared by the double emulsion and solvent evaporation technique were administered orally at 2/3rd therapeutic dose to guinea pigs. A single oral administration of the formulation resulted in sustained drug levels in the plasma for 7-12 days and in the organs for 11-14 days with a significant improvement in mean residence time as well as drug bioavailability. The administration of PLG nanoparticles every 10 days (five doses) to Mycobacterium tuberculosis H(37)Rv infected guinea pigs led to undetectable bacilli in the organs, as did 46 conventional doses. Therefore, nanoparticle based antitubercular chemotherapy forms a sound basis for a reduction in dosing frequency and also offers the possibility of reducing the drug dosage.

Osmotically regulated asymmetric capsular systems for simultaneous sustained delivery of anti-tubercular drugs

Sustained release asymmetric membrane capsular systems were developed for simultaneous oral delivery of rifampicin and isoniazid sodium in order to reduce the problems associated with the multi drug therapy of tuberculosis. Dense semipermeable membrane coating capsules were also prepared for the delivery of these drugs by adopting two different filling approaches. In vitro release studies were carried out for both types of systems and the results were compared. Asymmetric membrane capsules provided sustained release of rifampicin associated with initial burst release, where isoniazid release rates were comparatively high due to higher aqueous solubility. Dense semipermeable membrane systems provided controlled release of both drugs but were devoid of initial burst release of isoniazid. To overcome these drawbacks, a modified asymmetric system was developed by adding appropriate amount of hydrophilic polymer mixture with isoniazid. The system provided satisfactory sustained release of rifampicin and isoniazid with initial burst release may be sufficient to achieve minimum effective concentration in blood. In vitro dissolution kinetics of the systems followed first order kinetics and statistical analysis of release rate data proved that modified asymmetric system was better amongst the developed systems.

Recent advances in tuberculosis research in India

Tuberculosis (TB) continues to be the leading killer of mankind among all infectious diseases, especially in the developing countries. Since the discovery of tubercle bacillus more than 100 years ago, TB has been the subject of research in an attempt to develop tools and strategies to combat this disease. Research in Indian laboratories has contributed significantly towards developing the DOTS strategy employed worldwide in tuberculosis control programmes and elucidating the biological properties of its etiologic agent, M. tuberculosis. In recent times, the development of tools for manipulation of mycobacteria has given a boost to researchers working in this field. New strategies are being employed towards understanding the mechanisms of protection and pathogenesis of this disease. Molecular methods are being applied to develop new tools and reagents for prevention, diagnosis and treatment of tuberculosis. With the sequencing of the genome of M. tuberculosis, molecules are being identified for the development of new drugs and vaccines. In this chapter, the advances made in these areas by Indian researchers mainly during the last five years are reviewed.

Chemotherapeutic potential of orally administered poly(lactide-co-glycolide) microparticles containing isoniazid, rifampin, and pyrazinamide against experimental tuberculosis

Poly(lactide-co-glycolide) (PLG) microspheres (diameter, less than 3 microm) containing isoniazid, rifampin, and pyrazinamide were used in a sustained oral drug delivery system to treat murine tuberculosis. Drug levels above the MIC were observed up to 72 h in plasma and for 9 days in various organs. Relative bioavailability of encapsulated drugs was greater than that of free drugs. Chemotherapy results showed better or equivalent clearance of bacilli in the PLG-drug-administered group (weekly) than with free drugs (daily).

Nanoparticle encapsulated antitubercular drugs as a potential oral drug delivery system against murine tuberculosis

Patient non-compliance is the major drawback associated with the long-duration chemotherapy of tuberculosis (TB); hence, reduction in dosing frequency forms an important therapeutic strategy. The present study reports the formulation of three frontline antitubercular drugs (ATD), i.e. rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA) encapsulated in poly (DL-lactide-co-glycolide) (PLG) nanoparticles. Drug encapsulation efficiencies were 56.9+/-2.7% for RIF, 66.3+/-5.8% for INH and 68+/-5.6% for PZA. Following a single oral administration of these preparations to mice, the drugs could be detected in the circulation for 6 days (RIF) and 9 days (INH/PZA), whereas therapeutic concentrations in the tissues were maintained for 9-11 days. Further, on oral administration of drug-loaded nanoparticles to Mycobacterium tuberculosis-infected mice at every 10th day, no tubercle bacilli could be detected in the tissues after 5 oral doses of treatment. Therefore, nanoparticle-based ATD therapy forms a sound basis for reduction in dosing frequency for better management of TB.

Chemotherapeutic activity against murine tuberculosis of once weekly administered drugs (isoniazid and rifampicin) encapsulated in liposomes

Co-administration of isoniazid (INH) and rifampicin (RIF) encapsulated in lung specific stealth liposomes at one third of their recommended doses of 12 and 10 mg/kg b.wt., respectively, exhibited a sustained release of these drugs in plasma (5 days) and lungs, liver and spleen (7 days). At these concentrations, T(max) and area under curve (AUC) values of liposomal drugs were more than that observed with free drugs. The elimination constant (Kel) was higher for liposomal INH (-0.034+/-0.008) and RIF (-0.017+/-0.009) compared with free INH (-0.392) and RIF (-0.243). Chemotherapeutic efficacy of once weekly-administered liposomal drugs for 6 weeks reduced the mycobacterial load significantly in lungs, liver and spleen of infected mice compared with untreated animals.