pH-dependent interactions of indinavir and lipids in nanoparticles and their ability to entrap a solute

Nanomedicine based approaches for combating viral infections

Millions of people die each year from viral infections across the globe. There is an urgent need to overcome the existing gap and pitfalls of the current antiviral therapy which include increased dose and dosing frequency, bioavailability challenges, non-specificity, incidences of resistance and so on. These stumbling blocks could be effectively managed by the advent of nanomedicine. Current review emphasizes over an enhanced understanding of how different lipid, polymer and elemental based nanoformulations could be potentially and precisely used to bridle the said drawbacks in antiviral therapy. The dawn of nanotechnology meeting vaccine delivery, role of RNAi therapeutics in antiviral treatment regimen, various regulatory concerns towards clinical translation of nanomedicine along with current trends and implications including unexplored research avenues for advancing the current drug delivery have been discussed in detail.

Nanosystems Applied to HIV Infection: Prevention and Treatments

Sexually-transmitted infections (STIs) are a global health concern worldwide as they cause acute diseases, infertility, and significant mortality. Among the bacterial, viral, and parasitic pathogens that can be sexually transmitted, human immunodeficiency virus (HIV) has caused one of the most important pandemic diseases, which is acquired immune deficiency syndrome (AIDS). 32.7 million people have died from AIDS-related illnesses since the start of the epidemic. Moreover, in 2019, 38 million people were living with HIV worldwide. The need to deal with this viral infection becomes more obvious, because it represents not only a problem for public health, but also a substantial economic problem. In this context, it is necessary to focus efforts on developing methods for prevention, detection and treatment of HIV infections that significantly reduce the number of newly infected people and provide a better quality of life for patients. For several decades, biomedical research has been developed allowing quick solutions through the contribution of effective tools. One of them is the use of polymers as vehicles, drug carrier agents, or as macromolecular prodrugs. Moreover, nanosystems (NSs) play an especially important role in the diagnosis, prevention, and therapy against HIV infection. The purpose of this work is to review recent research into diverse NSs as potential candidates for prevention and treatment of HIV infection. Firstly, this review highlights the advantages of using nanosized structures for these medical applications. Furthermore, we provide an overview of different types of NSs used for preventing or combating HIV infection. Then, we briefly evaluate the most recent developments associated with prevention and treatment alternatives. Additionally, the implications of using different NSs are also addressed.

Nano-ART and NeuroAIDS

Human immunodeficiency virus (HIV) is a neurotropic virus that enters the central nervous system (CNS) early in the course of infection. Although highly active antiretroviral therapy (HAART) has resulted in remarkable decline in the morbidity and mortality in AIDS patients, controlling HIV infections still remains a global health priority. HIV access to the CNS serves as the natural viral preserve because most antiretroviral (ARV) drugs possess inadequate or zero delivery across the brain barriers. The structure of the blood-brain barrier (BBB), the presence of efflux pumps, and the expression of metabolic enzymes pose hurdles for ARV drug-brain entry. Thus, development of target-specific, effective, safe, and controllable drug delivery approach is an important health priority for global elimination of AIDS progression. Nanoformulations can circumvent the BBB to improve CNS-directed drug delivery by affecting such pumps and enzymes. Alternatively, they can be optimized to affect their size, shape, and protein and lipid coatings to facilitate drug uptake, release, and ingress across the barrier. Improved drug delivery to the CNS would affect pharmacokinetic and drug biodistribution properties. This review focuses on how nanotechnology can serve to improve the delivery of antiretroviral medicines, termed NanoART, across the BBB and affect the biodistribution and clinical benefit for NeuroAIDS.

Tenofovir disoproxil fumarate loaded PLGA nanoparticles for enhanced oral absorption: Effect of experimental variables and in vitro, ex vivo and in vivo evaluation

In this study, PLGA based nanoparticles of tenofovir disoproxil fumarate (TDF) were designed for enhancing its oral absorption. To develop PLGA based TDF nanoparticles with the goal of minimum particle size and maximum entrapment efficiency statistical optimization techniques (factorial design and response surface methodology) were employed. The optimized nanoparticles were characterized for size, shape, charge and physical state. Further, the stability, cytotoxicity and metabolic protective effect of the nanoparticles were evaluated. Single dose pharmacokinetic study in rats was conducted to evaluate the oral absorption of the designed nanoparticles. Ex vivo everted gut sac studies were performed to evaluate the role of active uptake mechanisms in the absorption of the designed nanoparticles. The results showed that the statistical models employed could determine the interaction effects of the critical factors which were used in the optimization of the nanoparticles. The optimized nanoparticles with a particle size of 218±3.85nm and an entrapment efficiency of 57.3±1.6%. The nanoparticles were able to increase the AUC of tenofovir by 5.8 fold. It was observed that active uptake mechanisms predominantly via clathrin-mediated uptake played a key role in increasing the oral absorption of TDF.

Stimuli-sensitive thiolated hyaluronic acid based nanofibers: synthesis, preclinical safety and in vitro anti-HIV activity

AIM

To develop a seminal enzyme bioresponsive, mucoadhesive nanofibers (NFs) as safe and effective nanocarriers for the prevention of HIV vaginal transmission.

METHODS

A novel thiolated hyaluronic acid (HA-SH) polymer was synthesized to fabricate tenofovir (TFV)-loaded electrospun NFs (HA-SH-NFs) and characterized in vitro/in vivo.

RESULTS

A triggered drug release (87% w/w) from the engineered HA-SH-NFs (mean diameter ∼75 nm) occured within 1 h under the influence of seminal hyaluronidase enzyme. HA-SH-NFs were noncytotoxic, induced no damage on the C57BL/6 mice genital-tract and other organs. No significant CD45 cell-infiltration and changes in cytokines level in cervicovaginal tissues were observed. HA-SH-NFs significantly enhanced both TFV retention and bioavailability in vaginal tissue compared with the 1% TFV-gel. The anti-HIV activity of TFV (on pseudotyped virus followed by luciferase assay) was not adversely affected by the electrospinning process.

CONCLUSION

HA-SH-NFs developed in this study could potentially serve as a safe nanotemplate for topical intravaginal delivery of HIV/AIDS microbicides.

Smart nanoparticles as targeting platforms for HIV infections

While Human Immunodeficiency Virus (HIV) infections are reducing in incidence with the advent of Highly Active Anti-retroviral Therapy (HAART), there remain a number of challenges including the existence of reservoirs, drug resistance and anatomical barriers to antiretroviral therapy. To overcome these, smart nanoparticles with stimuli responsive release are proposed for delivery of anti-retroviral agents. The paper highlights the strategic similarities between the design of smart antiretroviral nanocarriers and those optimized for cancer chemotherapy. This includes the development of nanoparticles capable of passive and active targeting as well as those that are responsive to various internal and external triggers. For antiretroviral therapy, the relevant triggers for stimuli responsive release of drugs include semen, enzymes, endosomal escape, temperature and magnetic field. Deriving from the experience of cancer chemotherapy, additional potential triggers are light and ultrasound which remain hitherto unexplored in HIV therapy. In addition, the roles of nanomicrobicides (nanogels) and virus mimetic nanoparticles are discussed from the point of view of prevention of HIV transmission. The challenges associated with translation of smart nanoparticles for HIV infections to realize the Millennium Development Goal of combating HIV infections are discussed.

pH-responsive artemisinin dimer in lipid nanoparticles are effective against human breast cancer in a xenograft model

Artemisinin (ART), a well-known antimalaria drug, also exhibits anticancer activities. We previously reported a group of novel dimeric artemisinin piperazine conjugates (ADPs) possessing pH-dependent aqueous solubility and a proof-of-concept lipid nanoparticle formulation based on natural egg phosphatidylcholine (EPC). EPC may induce allergic reactions in individuals sensitive to egg products. Therefore, the goal of this report is to develop ADP-synthetic lipid particles suitable for in vivo evaluation. We found that ADP binds to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) with greater than 90% efficiency and forms drug-lipid particles (d ∼ 80 nm). Cryo-electron microscopy of the ADP drug-lipid particles revealed unilamellar vesicle-like structures. Detailed characterization studies show insertion of the ADP lead compound, ADP109, into the DPPC membrane and the presence of an aqueous core. Over 50% of the ADP109 was released in 48 hours at pH4 compared with less than 20% at neutral. ADP109-lipid particles exhibited high potency against human breast cancer, but was tolerated well by nontumorigenic cells. In MDA-MB-231 mouse xenograft model, lipid-bound ADP109 particles were more effective than paclitaxel in controlling tumor growth. Cellular uptake studies showed endocytosis of the nanoparticles and release of core-trapped marker throughout the cytosol at 37°C. These results demonstrate, for the first time, the in vivo feasibility of lipid-bound ART dimer for cancer chemotherapy.

Anti-HIV drug-combination nanoparticles enhance plasma drug exposure duration as well as triple-drug combination levels in cells within lymph nodes and blood in primates

HIV patients on combination oral drug therapy experience insufficient drug levels in lymph nodes, which is linked to viral persistence. Following success in enhancing lymph node drug levels and extending plasma residence time of indinavir formulated in lipid nanoparticles, we developed multidrug anti-HIV lipid nanoparticles (anti-HIV LNPs) containing lopinavir (LPV), ritonavir (RTV), and tenofovir (PMPA). These anti-HIV LNPs were prepared, characterized, scaled up, and evaluated in primates with a focus on plasma time course and intracellular drug exposure in blood and lymph nodes. Four macaques were subcutaneously administered anti-HIV LNPs and free drug suspension in a crossover study. The time course of the plasma drug concentration as well as intracellular drug concentrations in blood and inguinal lymph nodes were analyzed to compare the effects of LNP formulation. Anti-HIV LNPs incorporated LPV and RTV with high efficiency and entrapped a reproducible fraction of hydrophilic PMPA. In primates, anti-HIV LNPs produced over 50-fold higher intracellular concentrations of LPV and RTV in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained up to 7 days, beyond that achievable by their free drug counterpart. Thus, multiple antiretroviral agents can be simultaneously incorporated into anti-HIV lipid nanoparticles to enhance intracellular drug concentrations in blood and lymph nodes, where viral replication persists. As these anti-HIV lipid nanoparticles also prolonged plasma drug exposure, they hold promise as a long-acting dosage form for HIV patients in addressing residual virus in cells and tissue.

Long-acting three-drug combination anti-HIV nanoparticles enhance drug exposure in primate plasma and cells within lymph nodes and blood

Insufficient HIV drug levels in lymph nodes have been linked to viral persistence. To overcome lymphatic drug insufficiency, we developed and evaluated in primates a lipid-drug nanoparticle containing lopinavir, ritonavir, and tenofovir. These nanoparticles produced over 50-fold higher intracellular lopinavir, ritonavir and tenofovir concentrations in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained for 7 days after a single subcutaneous dose, exceeding that achievable with current oral therapy.

Linking the population pharmacokinetics of tenofovir and its metabolites with its cellular uptake and metabolism

Empirical pharmacokinetic models are used to explain the pharmacokinetics of the antiviral drug tenofovir (TFV) and its metabolite TFV diphosphate (TFV-DP) in peripheral blood mononuclear cells. These empirical models lack the ability to explain differences between the disposition of TFV-DP in HIV-infected patients vs. healthy individuals. Such differences may lie in the mechanisms of TFV transport and phosphorylation. Therefore, we developed an exploratory model based on mechanistic mass transport principles and enzyme kinetics to examine the uptake and phosphorylation kinetics of TFV. TFV-DP median C_max from the model was 38.5 fmol/10⁶ cells, which is bracketed by two reported healthy volunteer studies (38 and 51 fmol/10⁶ cells). The model presented provides a foundation for exploration of TFV uptake and phosphorylation kinetics for various routes of TFV administration and can be updated as more is known on actual mechanisms of cellular transport of TFV.

Evaluation of atazanavir and darunavir interactions with lipids for developing pH-responsive anti-HIV drug combination nanoparticles

We evaluated two human immunodeficiency virus (HIV) protease inhibitors, atazanavir (ATV) and darunavir (DRV), for pH-dependent solubility, lipid binding, and drug release from lipid nanoparticles (LNPs). Both ATV and DRV incorporated into LNPs composed of pegylated and non-pegylated phospholipids with nearly 100% efficiency, but only ATV-LNPs formed stable lipid-drug particles and exhibited pH-dependent drug release. DRV-LNPs were unstable and formed mixed micelles at low drug-lipid concentrations, and thus are not suitable for lipid-drug particle development. When ATV-LNPs were prepared with ritonavir (RTV), a metabolic and cellular membrane exporter inhibitor, and tenofovir (TFV), an HIV reverse-transcriptase inhibitor, stable, scalable, and reproducible anti-HIV drug combination LNPs were produced. Drug incorporation efficiencies of 85.5 ± 8.2, 85.1 ± 7.1, and 6.1 ± 0.8% for ATV, RTV, and TFV, respectively, were achieved. Preliminary primate pharmacokinetic studies with these pH-responsive anti-HIV drug combination LNPs administered subcutaneously produced detectable plasma concentrations that lasted for 7 days for all three drugs. These anti-HIV LNPs could be developed as a long-acting targeted antiretroviral therapy.

Aerosol-stable peptide-coated liposome nanoparticles: a proof-of-concept study with opioid fentanyl in enhancing analgesic effects and reducing plasma drug exposure

Previously, we reported a novel pressurized olfactory drug (POD) delivery device that deposits aerosolized drug preferentially to upper nasal cavity. This POD device provided sustained central nervous system (CNS) levels of soluble morphine analgesic effects. However, analgesic onset of less soluble fentanyl was more rapid but brief, likely because of hydrophobic fentanyl redistribution readily back to blood. To determine whether fentanyl incorporated into an aerosol-stable liposome that binds to nasal epithelial cells will enhance CNS drug exposure and analgesic effects and reduce plasma exposure, we constructed Arg-Gly-Asp (RGD) liposomes anchored with acylated integrin-binding peptides (palmitoyl-Gly-Arg-Gly-Asp-Ser). The RGD liposomes, which assume gel phase membrane structure at 25 °C, were stable under the stress of aerosolization as only 2.2 ± 0.5% calcein leakage was detected. The RGD-mediated integrin binding of liposome is also verified to be unaffected by aerosolization. Rats treated with fentanyl in RGD liposome and POD device exhibited greater analgesic effect, as compared with the free drug counterpart (AUC(effect) = 1387.1% vs. 760.1% MPE*min), whereas approximately 20% reduced plasma drug exposure was noted (AUC(0-120) = 208.2 vs. 284.8 ng min/mL). Collectively, fentanyl incorporated in RGD liposomes is physically and biologically stable under aerosolization, enhanced the overall analgesic effects, and reduced plasma drug exposure for the first 2 h.

Comparative biophysical properties of tenofovir-loaded, thiolated and nonthiolated chitosan nanoparticles intended for HIV prevention

AIM

This study is designed to test the hypothesis that tenofovir-loaded (an anti-HIV microbicide) chitosan-thioglycolic acid-conjugated (CS-TGA) nanoparticles (NPs) exhibit superior biophysical properties for mucoadhesion compared with those of native CS NPs.

MATERIALS & METHODS

The NPs are prepared by ionotropic gelation. The particle mean diameter, encapsulation efficiency and release profile are analyzed by dynamic light scattering and UV spectroscopy, respectively. The cytotoxicity, cellular uptake and uptake mechanism are assessed on VK2/E6E7 and End1/E6E7 cell lines by colorimetry/fluorimetry, and percentage mucoadhesion is assessed using porcine vaginal tissue.

RESULTS

The mean diameter of the optimal NP formulations ranges from 240 to 252 nm, with a maximal encapsulation efficiency of 22.60%. Tenofovir release from CS and CS-TGA NPs follows first-order and Higuchi models, respectively. Both NPs are noncytotoxic in 48 h. The cellular uptake, which is time dependent, mainly occurs via the caveolin-mediated pathway. The percentage of mucoadhesion of CS-TGA NPs is fivefold higher than that of CS NPs, and reached up to 65% after 2 h.

CONCLUSION

Collectively, CS-TGA NPs exhibit superior biophysical properties and can potentially maximize the retention time of a topical microbicide, such as tenofovir, intended for the prevention of HIV transmission.

Hyaluronidase-sensitive nanoparticle templates for triggered release of HIV/AIDS microbicide in vitro

This study was designed to test the hypothesis that a triggered release of a topical microbicide (tenofovir) from hyaluronic acid nanoparticles (HA-NPs) can be achieved under the influence of hyaluronidase (HAase) enzyme. A fractional factorial experimental design was used to examine the factors [molar concentrations of adipic acid dihydrazide (X1) and 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (X2), volume of acetone (X3) and reaction time (X4)] influencing the responses, Y1; particle mean diameter: PMD (nanometers: nm), Y2; polydispersity index: PDI and Y3; zeta (ζ) potential: (millivolts). The amide bond formation between HA and ADH after cross-linking was confirmed by FT-IR and (13)C-NMR analyses. These NPs were also characterized for cytotoxicity on a human vaginal epithelial cell line and L. crispatus. When formulated with factors X1; 2.49 mM, X2; 9.96 mM, X3; 60 mL, X4; 6 h, HA-NPs exhibited a spherical shape with PMD, PDI, ζ potential, encapsulation efficiency, and drug loading of 70.6 ± 4.1 nm, 0.07 ± 0.02, -38.2 ± 2.8 mV, 51.8 ± 2.4% w/w and 26.1 ± 1.2% w/w, respectively, (n = 3). Unlike for HA based gel, HAase significantly triggered the drug release and HA degradation from the NPs after 24 h (~90% w/w and 65% w/w, respectively); whereas, in its absence, these values were ~39% w/w and 26% w/w, respectively. The NPs were non-cytotoxic to human vaginal VK2/E6E7, End1/E6E7 cells and Lactobacillus crispatus. These data highlight the potential of HAase-sensitive HA-NPs templates for the controlled and vaginal delivery of anti-HIV/AIDS microbicides.

pH-responsive artemisinin derivatives and lipid nanoparticle formulations inhibit growth of breast cancer cells in vitro and induce down-regulation of HER family members

Artemisinin (ART) dimers show potent anti-proliferative activities against breast cancer cells. To facilitate their clinical development, novel pH-responsive artemisinin dimers were synthesized for liposomal nanoparticle formulations. A new ART dimer was designed to become increasingly water-soluble as pH declines. The new artemisinin dimer piperazine derivatives (ADPs) remained tightly associated with liposomal nanoparticles (NPs) at neutral pH but were efficiently released at acidic pH's that are known to exist within solid tumors and organelles such as endosomes and lysosomes. ADPs incorporated into nanoparticles down regulated the anti-apoptotic protein, survivin, and cyclin D1 when incubated at low concentrations with breast cancer cell lines. We demonstrate for the first time, for any ART derivative, that ADP NPs can down regulate the oncogenic protein HER2, and its counterpart, HER3 in a HER2+ cell line. We also show that the wild type epidermal growth factor receptor (EGFR or HER1) declines in a triple negative breast cancer (TNBC) cell line in response to ADP NPs. The declines in these proteins are achieved at concentrations of NP109 at or below 1 µM. Furthermore, the new artemisinin derivatives showed improved cell-proliferation inhibition effects compared to known dimer derivatives.

Polymeric particulate technologies for oral drug delivery and targeting: a pathophysiological perspective

The oral route for delivery of pharmaceuticals is the most widely used and accepted. Nanoparticles and microparticles are increasingly being applied within this arena to optimize drug targeting and bioavailability. Frequently the carrier systems used are either constructed from or contain polymeric materials. Examples of these nanocarriers include polymeric nanoparticles, solid lipid nanocarriers, self-nanoemulsifying drug delivery systems and nanocrystals. It is the purpose of this review to describe these cutting edge technologies and specifically focus on the interaction and fate of these polymers within the gastrointestinal system.

Nanotechnology and the treatment of HIV infection

Suboptimal adherence, toxicity, drug resistance and viral reservoirs make the lifelong treatment of HIV infection challenging. The emerging field of nanotechnology may play an important role in addressing these challenges by creating drugs that possess pharmacological advantages arising out of unique phenomena that occur at the “nano” scale. At these dimensions, particles have physicochemical properties that are distinct from those of bulk materials or single molecules or atoms. In this review, basic concepts and terms in nanotechnology are defined, and examples are provided of how nanopharmaceuticals such as nanocrystals, nanocapsules, nanoparticles, solid lipid nanoparticles, nanocarriers, micelles, liposomes and dendrimers have been investigated as potential anti-HIV therapies. Such drugs may, for example, be used to optimize the pharmacological characteristics of known antiretrovirals, deliver anti-HIV nucleic acids into infected cells or achieve targeted delivery of antivirals to the immune system, brain or latent reservoirs. Also, nanopharmaceuticals themselves may possess anti-HIV activity. However several hurdles remain, including toxicity, unwanted biological interactions and the difficulty and cost of large-scale synthesis of nanopharmaceuticals.

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.

Sensitive and rapid HPLC quantification of tenofovir from hyaluronic acid-based nanomedicine

The purpose of this study was to develop and validate a rapid, sensitive, and specific reversed-phase high-performance liquid chromatography method for the quantitative determination of native tenofovir (TNF) for various applications. Different analytical performance parameters such as linearity, precision, accuracy, limit of quantification (LOQ), limit of detection (LOD), and robustness were determined according to International Conference on Harmonization (ICH) guidelines. A Bridge™ C18 column (150 × 4.6 mm, 5 μm) was used as stationary phase. The retention time of TNF was 1.54 ± 0.03 min (n = 6). The assay was linear over the concentration range of 0.1-10 μg/mL. The proposed method was sensitive with LOD and LOQ values equal to 50 and 100 ng/mL, respectively. The method was accurate with percent mean recovery from 95.41% to 102.90% and precise as percent RSD (relative standard deviation) values for intra-day, and inter-day precision were less than 2%. This method was utilized for the estimation of molar absorptivity of TNF at 259 nm (ε(259) = 12,518 L/mol/cm), calculated from linear regression analysis. The method was applied for determination of percentage of encapsulation efficiency (22.93 ± 0.04%), drug loading (12.25 ± 1.03%), in vitro drug release profile in the presence of enzyme (43% release in the first 3 h) and purification analysis of hyaluronic acid-based nanomedicine.

pH-responsive nanoparticles releasing tenofovir intended for the prevention of HIV transmission

This study is designed to test the hypothesis that tenofovir (TNF) or tenofovir disoproxil fumarate (TDF) loaded nanoparticles (NPs) prepared with a blend of poly(lactic-co-glycolic acid) (PLGA) and methacrylic acid copolymer (Eudragit® S-100, or S-100) are noncytotoxic and exhibit significant pH-responsive release of anti-HIV microbicides in the presence of human semen fluid simulant (SFS). After NPs preparation by emulsification diffusion, their size, encapsulation efficiency (EE%), drug release profile, morphology, and cytotoxicity are characterized by dynamic light scattering, spectrophotometry, transmission electron microscopy, and cellular viability assay/transepithelial electrical resistance measurement, respectively. Cellular uptake was elucidated by fluorescence spectroscopy and confocal microscopy. The NPs have an average size of 250 nm, maximal EE% of 16.1% and 37.2% for TNF and TDF, respectively. There is a 4-fold increase in the drug release rate from the 75% S-100 blend in the presence of SFS over 72 h. At a concentration up to 10mg/ml, the PLGA/S-100 NPs are noncytotoxic for 48 h to vaginal endocervical/epithelial cells and Lactobacillus crispatus. The particle uptake (∼ 50% in 24h) by these vaginal cell lines mostly occurred through caveolin-mediated pathway. These data suggest the promise of using PLGA/S-100 NPs as an alternative controlled drug delivery system in intravaginal delivery of an anti-HIV/AIDS microbicide.

AIDS treatment with novel anti-HIV compounds improved by nanotechnology

The first International Symposium of Nanomedicine on AIDS "AIDS Treatment with Novel Anti-HIV compounds Improved by Nanotechnology" was held November 19-20, 2009 in Beijing, China. This symposium provided an international forum for presentation and discussion of exciting new advances in the emerging research area of nanobiomedical research on AIDS treatment as the focus point, as well as some issues in relevant fields such as nanobiomedical research on tumor treatment and safety evaluation of nanomedicines. Key highlights of the symposium include (1) reviewing current status of nanobiotechnology programs and their relations, more or less, with AIDS treatment; (2) reviewing current AIDS epidemiology in China and examining effectiveness and efficiency of current prevention and treatment strategies; (3) highlighting the obstacles to improve AIDS prevention and treatment, and (4) exploring innovative ways for nanotechnology to advance AIDS treatment, especially to combat HIV resistance to drugs.

Nanotechnology-based systems for the treatment and prevention of HIV/AIDS

The HIV/AIDS pandemic is an increasing global burden with devastating health-related and socioeconomic effects. The widespread use of antiretroviral therapy has dramatically improved life quality and expectancy of infected individuals, but limitations of currently available drug regimens and dosage forms, alongside with the extraordinary adapting capacity of the virus, have impaired further success. Alongside, circumventing the escalating number of new infections can only be attained with effective and practical preventative strategies. Recent advances in the field of drug delivery are providing evidence that engineered nanosystems may contribute importantly for the enhancement of current antiretroviral therapy. Additionally, groundwork is also being carried out in the field nanotechnology-based systems for developing preventative solutions for HIV transmission. This manuscript reviews recent advances in the field of nanotechnology-based systems for the treatment and prevention of HIV/AIDS. Particular attention is given to antiretroviral drug targeting to HIV reservoirs and the usefulness of nanosystems for developing topical microbicides and vaccines.

NanoART, neuroAIDS and CNS drug delivery

A broad range of nanomedicines is being developed to improve drug delivery for CNS disorders. The structure of the blood-brain barrier (BBB), the presence of efflux pumps and the expression of metabolic enzymes pose hurdles for drug-brain entry. Nanoformulations can circumvent the BBB to improve CNS-directed drug delivery by affecting such pumps and enzymes. Alternatively, they can be optimized to affect their size, shape, and protein and lipid coatings to facilitate drug uptake, release and ingress across the barrier. This is important as the brain is a sanctuary for a broad range of pathogens including HIV-1. Improved drug delivery to the CNS would affect pharmacokinetic and drug biodistribution properties. This article focuses on how nanotechnology can serve to improve the delivery of antiretroviral medicines, termed nanoART, across the BBB and affect the biodistribution and clinical benefit for HIV-1 disease.

Diffusion of an ionic drug in micellar aqueous solutions

Supramolecular carriers such as micelles can be used to noncovalently bind drug molecules for pharmaceutical applications. However, these carriers can fundamentally affect diffusion-based drug transport due to host-guest coupled diffusion. We report a ternary interdiffusion study on an ionic drug in aqueous micellar solutions. Specifically, high-precision Rayleigh interferometry was used to determine the four multicomponent diffusion coefficients for the potassium naproxenate-tyloxapol-water ternary system at 25 degrees C and pH 7. In addition, we have measured drug solubility as a function of tyloxapol concentration. These measurements were used to characterize drug-surfactant thermodynamic interactions using the two-phase partitioning model. Furthermore, we propose a novel model on host-guest coupled diffusion that includes counterions. We show that quantitative agreement between model and experimental diffusion results can be achieved if the effect of micelle solvation on transport parameters is included in the model. This work represents an essential addition to our previous diffusion study on a nonionic drug and provides guidance for the development of accurate models of drug diffusion-based controlled release in the presence of nanocarriers.