Lymphoid tissue targeting of anti-HIV drugs using liposomes

MicroRNA-195 liposomes for therapy of Alzheimer's disease

The complex etiologies and mechanisms of Alzheimer's disease (AD) underscore the importance for devising multitarget drugs to achieve effective therapy. MicroRNAs (miRNAs) are capable of concurrently regulating the expression of multiple proteins by selectively targeting disease- associated genes in a sequence-specific fashion. Nonetheless, as RNA-based drugs, their stability in the circulation and capacity of traversing the blood-brain barrier (BBB) is largely compromised, thereby limiting their potential clinical applications. In this study, we formulated the nanoliposomes encapsulating polyethyleneimine (PEI)/miR-195 complex (DPMT@PEI/miR-195) that was engineered through dual modifications to contain P-aminophenyl-alpha-d-mannopyranoside (MAN) and cationic cell-penetrating peptide (TAT). DPMT@PEI/miR-195 exhibited the enhanced BBB- and cell membrane penetrating capability. As expected, we observed that DPMT@PEI/miR-195 administered through intravenous tail injection of produced greater effectiveness than donepezil and the same range of effect as aducanumab in alleviating the cognitive decline in 7-month-old APP/PS1 mice. Moreover, the combination treatment with DPMT@PEI/miR-195 and donepezil effectively ameliorated the deterioration of cognition in 16-month-old APP/PS1 mice, with enhanced effects than either DPMT@PEI/miR-195 or donepezil alone. Furthermore, DPMT@PEI/miR-195 effectively attenuated the positive signals of Aβ, AT8, and CD68 in APP/PS1 mice without notable side effects. Our findings indicate DPMT@PEI/miR-195 as a promising potentially new agent or approach for the prophylaxis and treatment of early and advanced stages of Alzheimer's disease.

Enhanced tissue distribution of ritonavir-loaded nanostructured lipid carriers-recommending its dose reduction

Human immunodeficiency virus (HIV) mainly attacks lymphocytes of the human immune system. The untreated infection leads to acquired immune deficiency syndrome (AIDS). Ritonavir (RTV) belongs to protease inhibitors (PIs), the crucial contributors of the combination therapy used in the treatment of HIV that is called highly active antiretroviral therapy (HAART). Formulations targeting the lymphatic system (LS) play a key role in delivering and maintaining therapeutic drug concentrations in HIV reservoirs. In our previous study, we developed RTV-loaded nanostructured lipid carriers (NLCs), which contain the natural antioxidant alpha-tocopherol (AT). In the current study, the cytotoxicity of the formulation was studied in HepG2, MEK293, and H9C2 cell lines. The formulation efficacy to reach the LS was evaluated through a cycloheximide-injected chylomicron flow blockade model in Wistar rats. Biodistribution and toxicity studies were conducted in rodents to understand drug distribution patterns in various organs and to establish the safety profile of the optimized formulation (RTV-NLCs). From the MTT assay, it was found that the cell viability of the formulation is comparable with the pure drug (RTV-API). More than 2.5-folds difference in AUC was observed in animals treated with RTV-NLCs with and without cycloheximide injection. Biodistribution studies revealed higher drug exposure in the lymphoidal organs with the RTV-NLCs. No significant increase in serum biomarkers for hepatotoxicity was observed in rats dosed with the RTV-NLCs. The current study reveals the lymphatic uptake of the RTV-NLCs and their safety in rodents. As the tissue distribution of RTV-NLCs is high, hence re-adjusting the RTV-NLCs dose to get the response equivalent to RTV-API may be more beneficial with respect to its safety and efficacy.

Liposomes in Cancer Therapy: How Did We Start and Where Are We Now

Since their first discovery in the 1960s by Alec Bangham, liposomes have been shown to be effective drug delivery systems for treating various cancers. Several liposome-based formulations received approval by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA), with many others in clinical trials. Liposomes have several advantages, including improved pharmacokinetic properties of the encapsulated drug, reduced systemic toxicity, extended circulation time, and targeted disposition in tumor sites due to the enhanced permeability and retention (EPR) mechanism. However, it is worth noting that despite their efficacy in treating various cancers, liposomes still have some potential toxicity and lack specific targeting and disposition. This explains, in part, why their translation into the clinic has progressed only incrementally, which poses the need for more research to focus on addressing such translational limitations. This review summarizes the main properties of liposomes, their current status in cancer therapy, and their limitations and challenges to achieving maximal therapeutic efficacy.

Lipid-Based Nanocarriers for Neurological Disorders: A Review of the State-of-the-Art and Therapeutic Success to Date

Neurodegenerative disorders including Alzheimer's, Parkinson's, and dementia are chronic and advanced diseases that are associated with loss of neurons and other related pathologies. Furthermore, these disorders involve structural and functional defections of the blood-brain barrier (BBB). Consequently, advances in medicines and therapeutics have led to a better appreciation of various pathways associated with the development of neurodegenerative disorders, thus focusing on drug discovery and research for targeted drug therapy to the central nervous system (CNS). Although the BBB functions as a shield to prevent toxins in the blood from reaching the brain, drug delivery to the CNS is hindered by its presence. Owing to this, various formulation approaches, including the use of lipid-based nanocarriers, have been proposed to address shortcomings related to BBB permeation in CNS-targeted therapy, thus showing the potential of these carriers for translation into clinical use. Nevertheless, to date, none of these nanocarriers has been granted market authorization following the successful completion of all stages of clinical trials. While the aforementioned benefits of using lipid-based carriers underscores the need to fast-track their translational development into clinical practice, technological advances need to be initiated to achieve appropriate capacity for scale-up and the production of affordable dosage forms.

Top-Down Synthesis of a Lamivudine-Zidovudine Nano Co-Crystal

Lamivudine (3TC) and zidovudine (AZT) are antiretroviral agents used to manage HIV/AIDS infection. A wet media milling top-down approach was used to develop and produce nano co-crystals of 3TC and AZT. Micro co-crystals were prepared by solvent evaporation and subsequently milled in the presence of two surfactants, viz., sodium lauryl sulfate (SLS) and α-tocopheryl polyethylene glycol succinate 1000 (TPGS 1000). Optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) to establish and identify parameters that may affect the manufacturing of nano co-crystals. The impact of SLS and TPGS 1000 concentration, milling time, and number of units of milling medium on the manufacturing of nano co-crystals, was investigated. The critical quality attributes (CQA) monitored were particle size (PS), Zeta potential (ZP), and polydispersity index (PDI). Powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, transmission electron microscopy, energy dispersive X-ray spectroscopy scanning electron microscopy, and cytotoxicity assays were used for additional characterization of the optimised nano co-crystal. The mean PS, PDI, and ZP of the optimised top-down nanocrystal were 271.0 ± 92.0 nm, 0.467 ± 0.073, and −41.9 ± 3.94 mV, respectively. In conclusion, a simple, inexpensive, rapid, and precise method of nano co-crystal manufacturing was developed, validated, and optimised using DoE and RSM, and the final product exhibited the target CQA.

Quality by Design Optimization of Cold Sonochemical Synthesis of Zidovudine-Lamivudine Nanosuspensions

Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used to manage HIV/AIDS infection. The compounds require frequent dosing, exhibit unpredictable bioavailability and a side effect profile that includes hepato- and haema-toxicity. A novel pseudo one-solvent bottom-up approach and Design of Experiments using sodium dodecyl sulphate (SDS) and α-tocopheryl polyethylene glycol succinate 1000 (TPGS 1000) to electrosterically stablize the nano co-crystals was used to develop, produce and optimize 3TC and AZT nano co-crystals. Equimolar solutions of 3TC in surfactant dissolved in de-ionised water and AZT in methanol were rapidly injected into a vessel and sonicated at 4 °C. The resultant suspensions were characterized using a Zetasizer and the particle size, polydispersity index and Zeta potential determined. Optimization of the nanosuspensions was conducted using a Central Composite Design to produce nano co-crystals with specific identified and desirable Critical Quality Attributes including particle size (PS) < 1000 nm, polydispersity index (PDI) < 0.500 and Zeta potential (ZP) < −30mV. Further characterization was undertaken using Fourier Transform infrared spectroscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, powder X-ray diffraction and transmission electron microscopy. In vitro cytotoxicity studies revealed that the optimized nano co-crystals reduced the toxicity of AZT and 3TC to HeLa cells.

Eradication of Human Immunodeficiency Virus Type-1 (HIV-1)-Infected Cells

Predictions made soon after the introduction of human immunodeficiency virus type-1 (HIV-1) protease inhibitors about potentially eradicating the cellular reservoirs of HIV-1 in infected individuals were too optimistic. The ability of the HIV-1 genome to remain in the chromosomes of resting CD4+ T cells and macrophages without being expressed (HIV-1 latency) has prompted studies to activate the cells in the hopes that the immune system can recognize and clear these cells. The absence of natural clearance of latently infected cells has led to the recognition that additional interventions are necessary. Here, we review the potential of utilizing suicide gene therapy to kill infected cells, excising the chromosome-integrated HIV-1 DNA, and targeting cytotoxic liposomes to latency-reversed HIV-1-infected cells.

Pharmacokinetic stability of macrocyclic peptide triazole HIV-1 inactivators alone and in liposomes

Previously, we reported the discovery of macrocyclic peptide triazoles (cPTs) that bind to HIV-1 Env gp120, inhibit virus cell infection with nanomolar potencies, and cause irreversible virion inactivation. Given the appealing virus-killing activity of cPTs and resistance to protease cleavage observed in vitro, we here investigated in vivo pharmacokinetics of the cPT AAR029b. AAR029b was investigated both alone and encapsulated in a PEGylated liposome formulation that was designed to slowly release inhibitor. Pharmacokinetic analysis in rats showed that the half-life of FITC-AAR029b was substantial both alone and liposome-encapsulated, 2.92 and 8.87 hours, respectively. Importantly, liposome-encapsulated FITC-AAR029b exhibited a 15-fold reduced clearance rate from serum compared with the free FITC-cPT. This work thus demonstrated both the in vivo stability of cPT alone and the extent of pharmacokinetic enhancement via liposome encapsulation. The results obtained open the way to further develop cPTs as long-acting HIV-1 inactivators against HIV-1 infection.

Immunostimulatory Agent Evaluation: Lymphoid Tissue Extraction and Injection Route-Dependent Dendritic Cell Activation

For evaluation of a new therapeutic agent for immunotherapy or vaccination, analysis of immune cell activation in lymphatic tissues is essential. Here, we investigated immunological effects of a novel lipid-DNA immunostimulant in nanoparticle form from different administration routes in the mouse: oral, intranasal, subcutaneous, footpad, intraperitoneal, and intravenous. These injections will directly influence the immune response, and harvesting lymphatic tissues and analysis of dendritic cell (DC) activation in the tissues are crucial parts of these evaluations. The extraction of mediastinal lymph nodes (mLNs) is important but quite complex because of the size and location of this organ. A stepwise procedure for harvesting the inguinal lymph node (iLN), mLN, and spleen and analyzing DC activation by flow cytometry is described.

Lipid-calcium phosphate nanoparticles for delivery to the lymphatic system and SPECT/CT imaging of lymph node metastases

A lipid/calcium/phosphate (LCP) nanoparticle (NP) formulation (particle diameter ∼25 nm) with superior siRNA delivery efficiency was developed and reported previously. Here, we describe the successful formulation of (111)In into LCP for SPECT/CT imaging. Imaging and biodistribution studies showed that, polyethylene glycol grafted (111)In-LCP preferentially accumulated in the lymph nodes at ∼70% ID/g in both C57BL/6 and nude mice when the improved surface coating method was used. Both the liver and spleen accumulated only ∼25% ID/g. Larger LCP (diameter ∼67 nm) was less lymphotropic. These results indicate that 25 nm LCP was able to penetrate into tissues, enter the lymphatic system, and accumulate in the lymph nodes via lymphatic drainage due to 1) small size, 2) a well-PEGylated lipid surface, and 3) a slightly negative surface charge. The capability of intravenously injected (111)In-LCP to visualize an enlarged, tumor-loaded sentinel lymph node was demonstrated using a 4T1 breast cancer lymph node metastasis model. Systemic gene delivery to the lymph nodes after IV injection was demonstrated by the expression of red fluorescent protein cDNA. The potential of using LCP for lymphatic drug delivery is discussed.

Lymphatic system: a prospective area for advanced targeting of particulate drug carriers

INTRODUCTION

The lymphatic system has a critical role in the immune system's recognition and response to disease and it is an additional circulatory system throughout the entire body. Extensive multidisciplinary investigations have been carried out in the area of lymphatic delivery, and lymphatic targeting has attracted a lot of attention for providing preferential chemotherapy and improving bioavailability of drugs that undergo hepatic first-pass metabolism.

AREAS COVERED

This review focuses on progress in the field of lymphatic therapeutics and diagnosis. Moreover, the anatomy and physiology of the lymphatic system, particulate drug carriers and different physicochemical parameters of both modified and unmodified particulate drug carriers and their effect on lymphatic targeting are addressed.

EXPERT OPINION

Particulate drug carriers have encouraged lymphatic targeting, but there are still challenges in targeting drugs and bioactives to specific sites, maintaining desired action and crossing all the physiological barriers. Lymphatic therapy using drug-encapsulated lipid carriers, especially liposomes and solid lipid nanoparticles, emerges as a new technology to provide better penetration into the lymphatics where residual disease exists. Size is the most important criteria when designing nanocarriers for targeting lymphatic vessels as the transportation of these particles into lymphatic vessels is size dependent. By increasing our understanding of lymphatic transport and uptake, and the role of lymphatics in various diseases, we can design new therapeutics for effective disease control.

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Delivery Systems for Lymphatic Targeting

The lymphatic system has a critical role in the immune system’s recognition and response to disease, and it is an additional circulatory system throughout the entire body. Most solid cancers primarily spread from the main site via the tumour’s surrounding lymphatics before haematological dissemination. Targeting drugs to lymphatic system is quite complicated because of its intricate physiology. Therefore, it tends to be an important target for developing novel therapeutics. Currently, nanocarriers have encouraged the lymphatic targeting, but still there are challenges of locating drugs and bioactives to specific sites, maintaining desired action and crossing all the physiological barriers. Lymphatic therapy using drug-encapsulated colloidal carriers especially liposomes and solid lipid nanoparticles emerges as a new technology to provide better penetration into the lymphatics where residual disease exists. Optimising the proper procedure, selecting the proper delivery route and target area and making use of surface engineering tool, better carrier for lymphotropic system can be achieved. Thus, new methods of delivering drugs and other carriers to lymph nodes are currently under investigation.

Enhanced anti-HIV efficacy of indinavir after inclusion in CD4-targeted lipid nanoparticles

BACKGROUND

Combination drug therapy has reduced plasma HIV to undetectable levels; however, drug-sensitive virus persists in patients' lymphoid tissue. We have reported significant lymphoid tissue drug localization with indinavir-associated lipid nanoparticles (LNPs). Our current objective is to evaluate whether additional enhancement is achievable by targeting these particles to CD4-HIV host cells.

METHODS

We characterized 2 peptide-coated (CD4-BP2 and CD4-BP4) drug-associated LNPs and demonstrated CD4-cell specificity. Drug-associated LNPs expressing polyethyleneglycol were exposed on HIV-2-infected cells under dynamic conditions that emulated lymph node physiology for 15, 30, and 60 minutes at concentrations from 0 to 25 μM and evaluated for antiviral activity and cell-associated drug concentrations. The specificity of CD4-mediated enhancement of indinavir LNPs antiviral activity was evaluated by blocking with anti-CD4 antibody.

RESULTS

Inclusion of CD4-binding peptides on LNPs enhanced antiviral activity for all incubation conditions, compared with control particles or soluble drug (eg, 60 minutes exposure, EC50 = 0.12-0.13 vs. 0.46 μM for targeted nanoparticles vs. soluble drug). The CD4-BP4 peptide exhibited higher efficiency in eliciting antiviral activity than CD4-BP2-coated particles (EC50 = 7.5 μM vs. >25 μM at 15 minutes drug exposure). This enhancement seems to be driven by CD4 availability and cell-associated indinavir concentrations, as blocking of CD4 significantly ablated indinavir efficacy in targeted particles and indinavir concentrations reflected the observed anti-HIV activity.

CONCLUSIONS

We constructed CD4-targeted LNPs that provide selective binding and efficient delivery of indinavir to CD4-HIV host cells. Inclusion of polyethyleneglycol in LNPs would minimize immune recognition of peptides. The enhancement of anti-HIV effects is effective even under limited time exposure.

In vivo anti-HIV activity of the heparin-activated serine protease inhibitor antithrombin III encapsulated in lymph-targeting immunoliposomes

Endogenous serine protease inhibitors (serpins) are anti-inflammatory mediators with multiple biologic functions. Several serpins have been reported to modulate HIV pathogenesis, or exhibit potent anti-HIV activity in vitro, but the efficacy of serpins as therapeutic agents for HIV in vivo has not yet been demonstrated. In the present study, we show that heparin-activated antithrombin III (hep-ATIII), a member of the serpin family, significantly inhibits lentiviral replication in a non-human primate model. We further demonstrate greater than one log(10) reduction in plasma viremia in the nonhuman primate system by loading of hep-ATIII into anti-HLA-DR immunoliposomes, which target tissue reservoirs of viral replication. We also demonstrate the utility of hep-ATIIII as a potential salvage agent for HIV strains resistant to standard anti-retroviral treatment. Finally, we applied gene-expression arrays to analyze hep-ATIII-induced host cell interactomes and found that downstream of hep-ATIII, two independent gene networks were modulated by host factors prostaglandin synthetase-2, ERK1/2 and NFκB. Ultimately, understanding how serpins, such as hep-ATIII, regulate host responses during HIV infection may reveal new avenues for therapeutic intervention.

Design and characterization of novel peptide-coated lipid nanoparticles for targeting anti-HIV drug to CD4 expressing cells

Human immunodeficiency virus (HIV) persists in lymph nodes and lymphoid tissues even during aggressive drug treatment, likely due to insufficient drug concentrations at this site. Therefore, to eliminate this residual virus, methods that enhance lymph node drug concentrations are currently being evaluated. Although enhanced drug concentrations in tissue have been achieved with drug-associated lipid nanoparticles, targeting these particles to CD4(+) cells may provide specific delivery of drug to HIV target cells and further enhance drug efficacy. We have evaluated four candidate peptides with reported binding specificity to CD4 for anchoring on lipid nanoparticle preparations previously shown to localize in lymph nodes. Terminal cysteine containing candidate peptides were conjugated to lipid nanoparticles through maleimide-linked phospholipids for targeting to CD4 cells. Using fluorescently labeled lipid nanoparticle binding to cells with varying degree of CD4 expression (CEMx174, Molt-4, Jurkat, and Ramos), we indentified two peptide sequences that provided CD4 selectivity to nanoparticles. These two peptide candidates on lipid nanoparticles bound to cells corresponding to the degree of CD4 expression and in a peptide dose dependent manner. Further, binding of these targeted lipid nanoparticles was CD4 specific, as pre-exposure of CD4(+) cells to anti-CD4 antibodies or free peptides inhibited the binding interactions. These results indicate targeting of lipid nanoparticles for specific binding to CD4 can be accomplished by tagging CD4 binding peptides with peptides, and these results provide a basis for further evaluation of this targeted delivery system to enhance antiviral drug delivery to CD4(+) HIV host cells, particularly those in lymph nodes and lymphoid tissues.

Surface modified nevirapine nanosuspensions for viral reservoir targeting: In vitro and in vivo evaluation

Most of the time HIV virus escape immunological burden exerted by antiretroviral drugs and develops resistance against therapy. For complete eradication of virus from body one has to use long term chemotherapies, which results in drug toxicity, drug resistance and eventually poor patient compliance. Nevirapine (NNRTI, non nucleoside reverse transcriptase inhibitor) nanosuspensions were developed and surface modified with serum albumin, polysaccharide and polyethylene glycol to enhance its targeting potential. The biodistribution studies revealed improved antiretroviral drug accumulation in various organs of rat for nanosuspensions as compared to the plain drug solution when administered intravenously. Nanosuspension after surface modification showed further enhancement in accumulation. Higher MRT values of surface coated nanosuspension in brain, liver and spleen as compared to pure drug solution ensured enhanced bioavailability and prolonged residence of the drug at the target site.

Lymphatic drug delivery using engineered liposomes and solid lipid nanoparticles

The lymphatic system plays a crucial role in the immune system's recognition and response to disease, and most solid cancers initially spread from the primary site via the tumor's surrounding lymphatics before hematological dissemination. Hence, the lymphatic system is an important target for developing new vaccines, cancer treatments, and diagnostic agents. Targeting the lymphatic system by subcutaneous, intestinal, and pulmonary routes has been evaluated and subsequently utilized to improve lymphatic penetration and retention of drug molecules, reduce drug-related systemic toxicities, and enhance bioavailability of poorly soluble and unstable drugs. Lymphatic imaging is an essential tool for the detection and staging of cancer. New nano-based technologies offer improved detection and characterization of the nodal diseases, while new delivery devices can better target and confine treatments to tumors within the nodal space while sparing healthy tissues. This manuscript reviews recent advances in the field of lymphatic drug delivery and imaging and focuses specifically on the development of liposomes and solid lipid nanoparticles for lymphatic introduction via the subcutaneous, intestinal, and pulmonary routes.

Activation of latent HIV using drug-loaded nanoparticles

Antiretroviral therapy is currently only capable of controlling HIV replication rather than completely eradicating virus from patients. This is due in part to the establishment of a latent virus reservoir in resting CD4+ T cells, which persists even in the presence of HAART. It is thought that forced activation of latently infected cells could induce virus production, allowing targeting of the cell by the immune response. A variety of molecules are able to stimulate HIV from latency. However no tested purging strategy has proven capable of eliminating the infection completely or preventing viral rebound if therapy is stopped. Hence novel latency activation approaches are required. Nanoparticles can offer several advantages over more traditional drug delivery methods, including improved drug solubility, stability, and the ability to simultaneously target multiple different molecules to particular cell or tissue types. Here we describe the development of a novel lipid nanoparticle with the protein kinase C activator bryostatin-2 incorporated (LNP-Bry). These particles can target and activate primary human CD4+ T-cells and stimulate latent virus production from human T-cell lines in vitro and from latently infected cells in a humanized mouse model ex vivo. This activation was synergistically enhanced by the HDAC inhibitor sodium butyrate. Furthermore, LNP-Bry can also be loaded with the protease inhibitor nelfinavir (LNP-Bry-Nel), producing a particle capable of both activating latent virus and inhibiting viral spread. Taken together these data demonstrate the ability of nanotechnological approaches to provide improved methods for activating latent HIV and provide key proof-of-principle experiments showing how novel delivery systems may enhance future HIV therapy.

Bifunctional molecules evade cytochrome P(450) metabolism by forming protective complexes with FK506-binding protein

Despite their large size and complexity, the macrolide natural products rapamycin and FK506 have excellent pharmacological characteristics. We hypothesize that these unexpected properties may arise from protective, high affinity interactions with the cellular FK506-binding protein, FKBP. In this model, the drug-FKBP complex might sequester the small molecule and limit its degradation by restricting access to metabolic enzymes. In support of this idea, we found that adding FKBP blocks binding of FK506 to the common cytochrome P(450) enzyme CYP3A4 in vitro. To further test this idea, we have systematically modified a small collection of otherwise unrelated compounds, such that they acquire affinity for FKBP. Strikingly, we found that many of these synthetic derivatives, but not the unmodified parent compounds, are also protected from CYP3A4-mediated metabolism. Depending on the properties of the linker, the bifunctional molecules exhibited up to a 3.5-fold weaker binding to CYP3A4, and this protective effect was observed in the presence of either purified FKBP or FKBP-expressing cells. Together, these results suggest that the surprising pharmacology of rapamycin and FK506 might arise, in part, from binding to their abundant, intracellular target, FKBP. Furthermore, these findings provide a framework by which other small molecules might be systematically modified to impart this protective effect.

Rapid and simple liquid chromatography tandem mass spectrometry method for the quantification of zidovudine in rat plasma

A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of zidovudine in rat plasma. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 268/127 for zidovudine and m/z 230/112 for the internal standard. The method exhibited a linear dynamic range of 5-500 ng/mL for zidovudine in rat plasma. The lower limit of quantification was 5 ng/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 1.5 min for each sample made it possible to analyze more than 400 plasma samples per day. The validated method was applied for pharmacokinetic studies of the novel drug delivery systems of zidovudine in rats.

Recent advances in delivery systems for anti-HIV1 therapy

In the last years, different non-biological and biological carrier systems have been developed for anti-HIV1 therapy. Liposomes are excellent potential anti-HIV1 carriers that have been tested with drugs, antisense oligonucleotides, ribozymes and therapeutic genes. Nanoparticles and low-density lipoproteins (LDLs) are cell-specific transporters of drugs against macrophage-specific infections such as HIV1. Through a process of protein transduction, cell-permeable peptides of natural origin or designed artificially allow the delivery of drugs and genetic material inside the cell. Erythrocyte ghosts and bacterial ghosts are a promising delivery system for therapeutic peptides and HIV vaccines. Of interest are the advances made in the field of HIV gene therapy by the use of autologous haematopoietic stem cells and viral vectors for HIV vaccines. Although important milestones have been reached in the development of carrier systems for the treatment of HIV, especially in the field of gene therapy, further clinical trials are required so that the efficiency and safety of these new systems can be guaranteed in HIV patients.

Long-circulating gadolinium-encapsulated liposomes for potential application in tumor neutron capture therapy

Gadolinium neutron capture therapy (Gd-NCT) is a promising cancer therapy modality. One of the key factors for a successful Gd-NCT is to deliver and maintain a sufficient amount of Gd in tumor tissues during neutron irradiation. We proposed to prepare a Gd delivery system by complexing a Gd-containing compound, diethylenetriaminepentaacetic acid (Gd-DTPA), with a polycationic peptide, poly-L-lysine (pLL), and then encapsulate the complexed Gd-DTPA into PEGylated liposomes. Complexation of Gd-DTPA with pLL not only enhanced the encapsulation efficiency of Gd-DTPA in liposomes, but also significantly limited the release of Gd-DTPA from the liposomes. A Gd-DTPA-encapsulated liposome formulation that contained 6.8+/-0.3 mg/mL of pure encapsulated Gd was prepared. The blood half-life of the Gd encapsulated into the liposome formulation was estimated to be about 24 h in healthy tumor-free mice. About 12 h after the Gd-encapsulated liposomes were intravenously injected into mice with pre-established model tumors, the Gd content in the tumors reached an average of 159 microg/g of wet tumor tissue. This Gd-DTPA encapsulated liposome may be used to deliver Gd into solid tumors for NCT and tumor imaging.

Nanoparticle uptake by the oral route: Fulfilling its potential?

The absorption of nanoparticles from the gastrointestinal tract is discussed first from a recent historical perspective, emphasising the crucial parameters that influence uptake, such as particle diameter, the nature of the particle and any surface modification with ligands designed to interact with receptors to facilitate targeting to and uptake into cells. Post-absorptive events, including translocation processes, are suggested here to be as important as initial uptake into the epithelial cells or M-cells of the gut associated lymphoid tissue.: