Nano-NRTIs demonstrate low neurotoxicity and high antiviral activity against HIV infection in the brain

Recent advances in nanotherapeutics for HIV-associated neurocognitive disorders and substance use disorders

Substance use disorders (SUD) and HIV-associated neurocognitive disorders (HAND) work synergistically as a significant cause of cognitive decline in adults and adolescents globally. Current therapies continue to be limited due to difficulties crossing the blood-brain barrier (BBB) leading to limited precision and effectiveness, neurotoxicity, and lack of co-treatment options for both HAND and SUD. Nanoparticle-based therapeutics have several advantages over conventional therapies including more precise targeting, the ability to cross the BBB, and high biocompatibility which decreases toxicity and optimizes sustainability. These advantages extend to other neurological disorders such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). This review summarizes recent advances in nanotechnology for application to HAND, SUD, and co-treatment, as well as other neurological disorders. This review also highlights the potential challenges these therapies face in clinical translation and long-term safety.

Nanotechnology in healthcare, and its safety and environmental risks

Nanotechnology holds immense promise in revolutionising healthcare, offering unprecedented opportunities in diagnostics, drug delivery, cancer therapy, and combating infectious diseases. This review explores the multifaceted landscape of nanotechnology in healthcare while addressing the critical aspects of safety and environmental risks associated with its widespread application. Beginning with an introduction to the integration of nanotechnology in healthcare, we first delved into its categorisation and various materials employed, setting the stage for a comprehensive understanding of its potential. We then proceeded to elucidate the diverse healthcare applications of nanotechnology, spanning medical diagnostics, tissue engineering, targeted drug delivery, gene delivery, cancer therapy, and the development of antimicrobial agents. The discussion extended to the current situation surrounding the clinical translation and commercialisation of these cutting-edge technologies, focusing on the nanotechnology-based healthcare products that have been approved globally to date. We also discussed the safety considerations of nanomaterials, both in terms of human health and environmental impact. We presented the in vivo health risks associated with nanomaterial exposure, in relation with transport mechanisms, oxidative stress, and physical interactions. Moreover, we highlighted the environmental risks, acknowledging the potential implications on ecosystems and biodiversity. Lastly, we strived to offer insights into the current regulatory landscape governing nanotechnology in healthcare across different regions globally. By synthesising these diverse perspectives, we underscore the imperative of balancing innovation with safety and environmental stewardship, while charting a path forward for the responsible integration of nanotechnology in healthcare.

Lipid Horizons: Recent Advances and Future Prospects in LBDDS for Oral Administration of Antihypertensive Agents

The lipid-based drug delivery system (LBDDS) is a well-established technique that is anticipated to bring about comprehensive transformations in the pharmaceutical field, impacting the management and administration of drugs, as well as treatment and diagnosis. Various LBDDSs verified to be an efficacious mechanism for monitoring hypertension systems are SEDDS (self-nano emulsifying drug delivery), nanoemulsion, microemulsions, vesicular systems (transferosomes and liposomes), and solid lipid nanoparticles. LBDDSs overcome the shortcomings that are associated with antihypertensive agents because around fifty percent of the antihypertensive agents experience a few drawbacks including short half-life because of hepatic first-pass metabolism, poor aqueous solubility, low permeation rate, and undesirable side effects. This review emphasizes antihypertensive agents that were encapsulated into the lipid carrier to improve their poor oral bioavailability. Incorporating cutting-edge technologies such as nanotechnology and targeted drug delivery, LBDDS holds promise in addressing the multifactorial nature of hypertension. By fine-tuning drug release profiles and enhancing drug uptake at specific sites, LBDDS can potentially target renin-angiotensin-aldosterone system components, sympathetic nervous system pathways, and endothelial dysfunction, all of which play crucial roles in hypertension pathophysiology. The future of hypertension management using LBDDS is promising, with ongoing reviews focusing on precision medicine approaches, improved biocompatibility, and reduced toxicity. As we delve deeper into understanding the intricate mechanisms underlying hypertension, LBDDS offers a pathway to develop next-generation antihypertensive therapies that are safer, more effective, and tailored to individual patient needs.

A Rationale and Approach to the Development of Specific Treatments for HIV Associated Neurocognitive Impairment

Neurocognitive impairment (NCI) associated with HIV infection of the brain impacts a large proportion of people with HIV (PWH) regardless of antiretroviral therapy (ART). While the number of PWH and severe NCI has dropped considerably with the introduction of ART, the sole use of ART is not sufficient to prevent or arrest NCI in many PWH. As the HIV field continues to investigate cure strategies, adjunctive therapies are greatly needed. HIV imaging, cerebrospinal fluid, and pathological studies point to the presence of continual inflammation, and the presence of HIV RNA, DNA, and proteins in the brain despite ART. Clinical trials exploring potential adjunctive therapeutics for the treatment of HIV NCI over the last few decades have had limited success. Ideally, future research and development of novel compounds need to address both the HIV replication and neuroinflammation associated with HIV infection in the brain. Brain mononuclear phagocytes (MPs) are the primary instigators of inflammation and HIV protein expression; therefore, adjunctive treatments that act on MPs, such as immunomodulating agents, look promising. In this review, we will highlight recent developments of innovative therapies and discuss future approaches for HIV NCI treatment.

A Comprehensive Review of Cross-Linked Gels as Vehicles for Drug Delivery to Treat Central Nervous System Disorders

Gels are attractive candidates for drug delivery because they are easily producible while offering sustained and/or controlled drug release through various mechanisms by releasing the therapeutic agent at the site of action or absorption. Gels can be classified based on various characteristics including the nature of solvents used during preparation and the method of cross-linking. The development of novel gel systems for local or systemic drug delivery in a sustained, controlled, and targetable manner has been at the epitome of recent advances in drug delivery systems. Cross-linked gels can be modified by altering their polymer composition and content for pharmaceutical and biomedical applications. These modifications have resulted in the development of stimuli-responsive and functionalized dosage forms that offer many advantages for effective dosing of drugs for Central Nervous System (CNS) conditions. In this review, the literature concerning recent advances in cross-linked gels for drug delivery to the CNS are explored. Injectable and non-injectable formulations intended for the treatment of diseases of the CNS together with the impact of recent advances in cross-linked gels on studies involving CNS drug delivery are discussed.

Nanogels as Novel Nanocarrier Systems for Efficient Delivery of CNS Therapeutics

Nanogels have come out as a great potential drug delivery platform due to its prominently high colloidal stability, high drug loading, core-shell structure, good permeation property and can be responsive to environmental stimuli. Such nanoscopic drug carriers have more excellent abilities over conventional nanomaterials for permeating to brain parenchyma in vitro and in vivo. Nanogel-based system can be nanoengineered to bypass physiological barriers via non-invasive treatment, rendering it a most suitable platform for the management of neurological conditions such as neurodegenerative disorders, brain tumors, epilepsy and ischemic stroke, etc. Therapeutics of central nervous system (CNS) diseases have shown marked limited site-specific delivery of CNS by the poor access of various drugs into the brain, due to the presences of the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Hence, the availability of therapeutics delivery strategies is considered as one of the most major challenges facing the treatment of CNS diseases. The primary objective of this review is to elaborate the newer advances of nanogel for CNS drugs delivery, discuss the early preclinical success in the field of nanogel technology and highlight different insights on its potential neurotoxicity.

Effect of drug-to-lipid ratio on nanodisc-based tenofovir drug delivery to the brain for HIV-1 infection

Background

Combination antiretroviral therapy has significantly advanced HIV-1 infection treatment. However, HIV-1 remains persistent in the brain; the inaccessibility of the blood–brain barrier allows for persistent HIV-1 infections and neuroinflammation. Nanotechnology-based drug carriers such as nanodiscoidal bicelles can provide a solution to combat this challenge.

Methods

This study investigated the safety and extended release of a combination antiretroviral therapy drug (tenofovir)-loaded nanodiscs for HIV-1 treatment in the brain both in vitro and in vivo.

Result

The nanodiscs entrapped the drug in their interior hydrophobic core and released the payload at the desired location and in a controlled release pattern. The study also included a comparative pharmacokinetic analysis of nanodisc formulations in in vitro and in vivo models.

Conclusion

The study provides potential applications of nanodiscs for HIV-1 therapy development.

Nano-based drug delivery system: a smart alternative towards eradication of viral sanctuaries in management of NeuroAIDS

Even though the dawn of highly active antiretroviral therapy (HAART) proved out to be a boon for acquired immunodeficiency syndrome (AIDS) patients, management of HIV infections persists to be a major global health curse. A reduced efficacy with existing conventional therapy for brain targeting has been largely credited to the inability of antiretroviral (ARV) drugs to transmigrate across the blood-brain barrier (BBB) in productive concentrations. The review consists of nano-based drug delivery strategies rendering superior outcomes to delivery of ARV drugs to the viral sanctuaries in the brain. Nano-ART for ARV drugs promotes the development of an optimized dosage regimen, thereby improving the penetration of drugs across the BBB in an attempt to target the central reservoirs hosting viral population. Numerous efforts have been undertaken for making the drug more bioavailable and therapeutically effective by moulding them into various nanostructures. Polymeric nanocarriers, solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, nanodiamonds, vesicle-based drug carriers, metal-based nanoparticles, and nano vaccines have been reported for their advancing role as a smart alternative for drug delivery to central nervous system. The high drug loading capacity of nanocarriers and their small size effectuating increased surface to volume ratio is accountable for improved efficacy of ARV drugs when formulated as nanotherapeutics. This review highlights the advancing role of nanotherapeutics in mediating a successful delivery of ARV drugs to eradicate viral loads in treating NeuroAIDS.

Nanoparticles and nanoformulated drugs as promising delivery system in treatment of microbial-induced CNS infection: a systematic review of literature

Central nervous system (CNS) infection is a global health problem with high rate of mortality and associated morbidities. Viruses, bacteria, fungi, and protozoa parasites are the main cause of CNS infection. Various medications are currently used for treatment of brain infections, but most of them do not have enough efficiency because the majority of conventional drugs cannot pass the blood-brain barrier (BBB) to combat the pathogens. Nanotechnology has provided promising approaches to solve this issue, since nanoparticles (NPs) can facilitate the drugs entrance through the BBB. Herein, we systematically reviewed all available literature to provide evidences for practicality of NPs in treatment of CNS infection. A systematic literature search was performed on January 29, 2021, in Web of Science, PubMed, Scopus, Science Direct, Embase, Ovid, and Google Scholar using "CNS infections" and "NPs/nanoformulation" including all their equivalent terms as keyword. Due to lack of human studies, no strict inclusion criteria were defined, and all relevant documents were included. After several steps of article selection, a total of 29 documents were collected and used for data synthesis. The results showed that drug-loaded NPs is fairly safe and can be a promising approach in developing anti-infective agents for treatment of CNS infection, since nanoformulated drugs could act up to tenfold more efficient that drug alone. Findings of this review indicate the importance of NPs and nanoformulation of drugs to enhance the efficiency of treatment and warrant the safety of treatment in human studies; however, clinical trials are required to confirm such efficiency and safety in clinical practice.

Synthesis of Nanogels: Current Trends and Future Outlook

Nanogels represent an innovative platform for tunable drug release and targeted therapy in several biomedical applications, ranging from cancer to neurological disorders. The design of these nanocarriers is a pivotal topic investigated by the researchers over the years, with the aim to optimize the procedures and provide advanced nanomaterials. Chemical reactions, physical interactions and the developments of engineered devices are the three main areas explored to overcome the shortcomings of the traditional nanofabrication approaches. This review proposes a focus on the current techniques used in nanogel design, highlighting the upgrades in physico-chemical methodologies, microfluidics and 3D printing. Polymers and biomolecules can be combined to produce ad hoc nanonetworks according to the final curative aims, preserving the criteria of biocompatibility and biodegradability. Controlled polymerization, interfacial reactions, sol-gel transition, manipulation of the fluids at the nanoscale, lab-on-a-chip technology and 3D printing are the leading strategies to lean on in the next future and offer new solutions to the critical healthcare scenarios.

Progress in the Application of Nanoparticles and Graphene as Drug Carriers and on the Diagnosis of Brain Infections

The blood–brain barrier (BBB) is the protective sheath around the brain that protects the sensitive microenvironments of the brain. However, certain pathogens, viruses, and bacteria disrupt the endothelial barrier and cause infection and hence inflammation in meninges. Macromolecular therapeutics are unable to cross the tight junctions, thereby limiting their bioavailability in the brain. Recently, nanotechnology has brought a revolution in the field of drug delivery in brain infections. The nanostructures have high targeting accuracy and specificity to the receptors in the case of active targeting, which have made them the ideal cargoes to permeate across the BBB. In addition, nanomaterials with biomimetic functions have been introduced to efficiently cross the BBB to be engulfed by the pathogens. This review focuses on the nanotechnology-based drug delivery approaches for exploration in brain infections, including meningitis. Viruses, bacteria, fungi, or, rarely, protozoa or parasites may be the cause of brain infections. Moreover, inflammation of the meninges, called meningitis, is presently diagnosed using laboratory and imaging tests. Despite attempts to improve diagnostic instruments for brain infections and meningitis, due to its complicated and multidimensional nature and lack of successful diagnosis, meningitis appears almost untreatable. Potential for overcoming the difficulties and limitations related to conventional diagnostics has been shown by nanoparticles (NPs). Nanomedicine now offers new methods and perspectives to improve our knowledge of meningitis and can potentially give meningitis patients new hope. Here, we review traditional diagnosis tools and key nanoparticles (Au-NPs, graphene, carbon nanotubes (CNTs), QDs, etc.) for early diagnosis of brain infections and meningitis.

Nanotechnology-based Targeting of Neurodegenerative Disorders: A Promising Tool for Efficient Delivery of Neuromedicines

Traditional drug delivery approaches remained ineffective in offering better treatment to various neurodegenerative disorders (NDs). In this context, diverse types of nanocarriers have shown their great potential to cross the blood-brain barrier (BBB) and have emerged as a prominent carrier system in drug delivery. Moreover, nanotechnology-based methods usually involve numerous nanosized carrier platforms, which potentiate the effect of the therapeutic agents in the therapy of NDs especially in diagnosis and drug delivery with negligible side effects. In addition, nanotechnology-based techniques have offered several strategies to cross BBB to intensify the bioavailability of drug moieties in the brain. In the last few years, diverse kinds of nanoparticles (NPs) have been developed by incorporating various biocompatible components (e.g., polysaccharide-based NPs, polymeric NPs, selenium NPs, AuNPs, protein-based NPs, gadolinium NPs, etc.), that showed great therapeutic benefits against NDs. Eventually, this review provides deep insights to explore recent applications of some innovative nanocarriers enclosing active molecules for the efficient treatment of NDs.

Nose to brain delivery of antiretroviral drugs in the treatment of neuroAIDS

NeuroAIDS (Neuro Acquired Immunodeficiency Syndrome) or HIV (Human Immunodeficiency Virus) associated neuronal abnormality is continuing to be a significant health issue among AIDS patients even under the treatment of combined antiretroviral therapy (cART). Injury and damage to neurons of the brain are the prime causes of neuroAIDS, which happens due to the ingress of HIV by direct permeation across the blood-brain barrier (BBB) or else via peripherally infected macrophage into the central nervous system (CNS). The BBB performs as a stringent barricade for the delivery of therapeutics drugs. The intranasal route of drug administration exhibits as a non-invasive technique to bypass the BBB for the delivery of antiretroviral drugs and other active pharmaceutical ingredients inside the brain and CNS. This method is fruitful for the drugs that are unable to invade the BBB to show its action in the CNS and thus erase the demand of systemic delivery and thereby shrink systemic side effects. Drug delivery from the nose to the brain/CNS takes very less time through both olfactory and trigeminal nerves. Intranasal delivery does not require the involvement of any receptor as it occurs by an extracellular route. Nose to brain delivery also involves nasal associated lymphatic tissues (NALT) and deep cervical lymph nodes. However, very little research has been done to explore the utility of nose to brain delivery of antiretroviral drugs in the treatment of neuroAIDS. This review focuses on the potential of nasal route for the effective delivery of antiretroviral nanoformulations directly from nose to the brain.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

Nanotechnology approaches to eradicating HIV reservoirs

The advent of combination antiretroviral therapy (cART) has transformed HIV-1 infection into a controllable chronic disease, but these therapies are incapable of eradicating the virus to bring about an HIV cure. Multiple strategies have been proposed and investigated to eradicate latent viral reservoirs from various biological sanctuaries. However, due to the complexity of HIV infection and latency maintenance, a single drug is unlikely to eliminate all HIV reservoirs and novel strategies may be needed to achieve better efficacy while limiting systemic toxicity. In this review, we describe HIV latency in cellular and anatomical reservoirs, and present an overview of current strategies for HIV cure with a focus on their challenges for clinical translation. Then we provide a summary of nanotechnology solutions that have been used to address challenges in HIV cure by delivering physicochemically diverse agents for combination therapy or targeting HIV reservoir sites. We also review nanocarrier-based gene delivery and immunotherapy used in cancer treatment but may have potential applications in HIV cure.

Nanoformulations: A Valuable Tool in the Therapy of Viral Diseases Attacking Humans and Animals

Various viruses can be considered as one of the most frequent causes of human diseases, from mild illnesses to really serious sicknesses that end fatally. Numerous viruses are also pathogenic to animals and plants, and many of them, mutating, become pathogenic also to humans. Several cases of affecting humans by originally animal viruses have been confirmed. Viral infections cause significant morbidity and mortality in humans, the increase of which is caused by general immunosuppression of the world population, changes in climate, and overall globalization. In spite of the fact that the pharmaceutical industry pays great attention to human viral infections, many of clinically used antivirals demonstrate also increased toxicity against human cells, limited bioavailability, and thus, not entirely suitable therapeutic profile. In addition, due to resistance, a combination of antivirals is needed for life-threatening infections. Thus, the development of new antiviral agents is of great importance for the control of virus spread. On the other hand, the discovery and development of structurally new antivirals represent risks. Therefore, another strategy is being developed, namely the reformulation of existing antivirals into nanoformulations and investigation of various metal and metalloid nanoparticles with respect to their diagnostic, prophylactic, and therapeutic antiviral applications. This chapter is focused on nanoscale materials/formulations with the potential to be used for the treatment or inhibition of the spread of viral diseases caused by human immunodeficiency virus, influenza A viruses (subtypes H3N2 and H1N1), avian influenza and swine influenza viruses, respiratory syncytial virus, herpes simplex virus, hepatitis B and C viruses, Ebola and Marburg viruses, Newcastle disease virus, dengue and Zika viruses, and pseudorabies virus. Effective antiviral long-lasting and target-selective nanoformulations developed for oral, intravenous, intramuscular, intranasal, intrarectal, intravaginal, and intradermal applications are discussed. Benefits of nanoparticle-based vaccination formulations with the potential to secure cross protection against divergent viruses are outlined as well.

Core-shell nanoparticles for targeted and combination antiretroviral activity in gut-homing T cells

A major sanctuary site for HIV infection is the gut-associated lymphoid tissue (GALT). The α4β7 integrin gut homing receptor is a promising therapeutic target for the virus reservoir because it leads to migration of infected cells to the GALT and facilitates HIV infection. Here, we developed a core-shell nanoparticle incorporating the α4β7 monoclonal antibody (mAb) as a dual-functional ligand for selectively targeting a protease inhibitor (PI) to gut-homing T cells in the GALT while simultaneously blocking HIV infection. Our nanoparticles significantly reduced cytotoxicity of the PI and enhanced its in vitro antiviral activity in combination with α4β7 mAb. We demonstrate targeting function of our nanocarriers in a human T cell line and primary cells isolated from macaque ileum, and observed higher in vivo biodistribution to the murine small intestines where they accumulate in α4β7+ cells. Our LCNP shows the potential to co-deliver ARVs and mAbs for eradicating HIV reservoirs.

Flow field-flow fractionation and multi-angle light scattering as a powerful tool for the characterization and stability evaluation of drug-loaded metal-organic framework nanoparticles

Asymmetric flow field-flow fractionation (AF4) coupled with UV-Vis spectroscopy, multi-angle light scattering (MALS) and refractive index (RI) detection has been applied for the characterization of MIL-100(Fe) nanoMOFs (metal-organic frameworks) loaded with nucleoside reverse transcriptase inhibitor (NRTI) drugs for the first time. Empty nanoMOFs and nanoMOFs loaded with azidothymidine derivatives with three different degrees of phosphorylation were examined: azidothymidine (AZT, native drug), azidothymidine monophosphate (AZT-MP), and azidothymidine triphosphate (AZT-TP). The particle size distribution and the stability of the nanoparticles when interacting with drugs have been determined in a time frame of 24 h. Main achievements include detection of aggregate formation in an early stage and monitoring nanoMOF morphological changes as indicators of their interaction with guest molecules. AF4-MALS proved to be a useful methodology to analyze nanoparticles engineered for drug delivery applications and gave fundamental data on their size distribution and stability. Graphical abstract ᅟ.

5'-Phosphorothiolate Dinucleotide Cap Analogues: Reagents for Messenger RNA Modification and Potent Small-Molecular Inhibitors of Decapping Enzymes

The 5' cap consists of 7-methylguanosine (m⁷G) linked by a 5'-5'-triphosphate bridge to messenger RNA (mRNA) and acts as the master regulator of mRNA turnover and translation initiation in eukaryotes. Cap analogues that influence mRNA translation and turnover (either as small molecules or as part of an RNA transcript) are valuable tools for studying gene expression, which is often also of therapeutic relevance. Here, we synthesized a series of 15 dinucleotide cap (m⁷GpppG) analogues containing a 5'-phosphorothiolate (5'-PSL) moiety (i.e., an O-to-S substitution within the 5'-phosphoester) and studied their biological properties in the context of three major cap-binding proteins: translation initiation factor 4E (eIF4E) and two decapping enzymes, DcpS and Dcp2. While the 5'-PSL moiety was neutral or slightly stabilizing for cap interactions with eIF4E, it significantly influenced susceptibility to decapping. Replacing the γ-phosphoester with the 5'-PSL moiety (γ-PSL) prevented β-γ-pyrophosphate bond cleavage by DcpS and conferred strong inhibitory properties. Combining the γ-PSL moiety with α-PSL and β-phosphorothioate (PS) moiety afforded first cap-derived hDcpS inhibitor with low nanomolar potency. Susceptibility to Dcp2 and translational properties were studied after incorporation of the new analogues into mRNA transcripts by RNA polymerase. Transcripts containing the γ-PSL moiety were resistant to cleavage by Dcp2. Surprisingly, superior translational properties were observed for mRNAs containing the α-PSL moiety, which were Dcp2-susceptible. The overall protein expression measured in HeLa cells for this mRNA was comparable to mRNA capped with the translation augmenting β-PS analogue reported previously. Overall, our study highlights 5'-PSL as a synthetically accessible cap modification, which, depending on the substitution site, can either reduce susceptibility to decapping or confer superior translational properties on the mRNA. The 5'-PSL-analogues may find application as reagents for the preparation of efficiently expressed mRNA or for investigation of the role of decapping enzymes in mRNA processing or neuromuscular disorders associated with decapping.

Nanoformulated Antiretrovirals for Penetration of the Central Nervous System: State of the Art

The central nervous system is a very challenging HIV-1 sanctuary. But, despite complete suppression of plasmatic viral replication with current antiretroviral therapy, signs of HIV-1 replication can still be found in the cerebrospinal fluid in some patients. The main limitation to achieving HIV-1 eradication from the brain is related to the suboptimal concentrations of antiretrovirals within this site, due to their low permeation across the blood-brain barrier. In recent years, a number of reliable nanotechnological strategies have been developed with the aim of enhancing antiretroviral drug penetration across the blood-brain barrier. The aim of this review is to provide an overview of the different nanoformulated antiretrovirals, used in both clinical and preclinical studies, that are designed to improve their delivery into the brain by active or passive permeation mechanisms through the barrier. Different nanotechnological approaches have proven successful for optimizing antiretrovirals delivery to the central nervous system, with a likely benefit for HIV-associated neurocognitive disorders and a more debated contribution to the complete eradication of the HIV-1 infection.

Nanogels: An overview of properties, biomedical applications and obstacles to clinical translation

Nanogels have emerged as a versatile hydrophilic platform for encapsulation of guest molecules with a capability to respond to external stimuli that can be used for a multitude of applications. These are soft materials capable of holding small molecular therapeutics, biomacromolecules, and inorganic nanoparticles within their crosslinked networks, which allows them to find applications for therapy as well as imaging of a variety of disease conditions. Their stimuli-responsive behavior can be easily controlled by selection of constituent polymer and crosslinker components to achieve a desired response at the site of action, which imparts nanogels the ability to participate actively in the intended function of the carrier system rather than being passive carriers of their cargo. These properties not only enhance the functionality of the carrier system but also help in overcoming many of the challenges associated with the delivery of cargo molecules, and this review aims to highlight the distinct and unique capabilities of nanogels as carrier systems for the delivery of an array of cargo molecules over other nanomaterials. Despite their obvious usefulness, nanogels are still not a commonplace occurrence in clinical practice. We have also made an attempt to highlight some of the major challenges that need to be overcome to advance nanogels further in the field of biomedical applications.

Recent trends on hydrogel based drug delivery systems for infectious diseases

Since centuries, the rapid spread and cure of infectious diseases have been a major concern to the progress and survival of humans. These diseases are a global burden and the prominent cause for worldwide deaths and disabilities. Nanomedicine has emerged as the most excellent tool to eradicate and halt their spread. Various nanoformulations (NFs) using advanced nanotechnology are in demand. Recently, hydrogel and nanogel based drug delivery devices have posed new prospects to simulate the natural intelligence of various biological systems. Owing to their unique porous interpenetrating network design, hydrophobic drug incorporation and stimulus sensitivity hydrogels owe excellent potential as targeted drug delivery systems. The present review is an attempt to highlight the recent trends of hydrogel based drug delivery systems for the delivery of therapeutic agents and diagnostics for major infectious diseases including acquired immune deficiency syndrome (AIDS), malaria, tuberculosis, influenza and ebola. Future prospects and challenges are also described.

Clinical challenges in HIV/AIDS: Hints for advancing prevention and patient management strategies

Acquired immune deficiency syndrome has been one of the most devastating epidemics of the last century. The current estimate for people living with the HIV is 36.9 million. Today, despite availability of potent and safe drugs for effective treatment, lifelong therapy is required for preventing HIV re-emergence from a pool of latently infected cells. However, recent evidence show the importance to expand HIV testing, to offer antiretroviral treatment to all infected individuals, and to ensure retention through all the cascade of care. In addition, circumcision, pre-exposure prophylaxis, and other biomedical tools are now available for included in a comprehensive preventive package. Use of all the available tools might allow cutting the HIV transmission in 2030. In this article, we review the status of the epidemic, the latest advances in prevention and treatment, the concept of treatment as prevention and the challenges and opportunities for the HIV cure agenda.

Humanized mice for HIV and AIDS research

HIV has a very limited species tropism that prevents the use of most conventional small animal models for AIDS research. The in vivo analysis of HIV/AIDS has benefited extensively from novel chimeric animal models that accurately recapitulate key aspects of the human condition. Specifically, immunodeficient mice that are systemically repopulated with human hematolymphoid cells offer a viable alternative for the study of a multitude of highly relevant aspects of HIV replication, pathogenesis, therapy, transmission, prevention, and eradication. This article summarizes some of the multiple contributions that humanized mouse models of HIV infection have made to the field of AIDS research. These models have proven to be highly informative and hold great potential for accelerating multiple aspects of HIV research in the future.

Biodegradable Nanoparticles for Delivery of Therapeutics in CNS Infection

Despite the significant advances in neurological medicine, it remains difficult to treat ailments directly involving the brain. The blood brain barrier (BBB) is a tightly regulated, selectively permeable barrier that restricts access from the blood into the brain extracellular fluid (BEF). Many conditions such as tumors or infections in the brain are difficult to treat due to the fact that drugs and other therapeutic agents are unable to easily pass through this relatively impermeable barrier. Human Immunodeficiency Virus (HIV) presents a particular problem as it is able to remain dormant in the brain for years protected from antiretroviral drugs by the BBB. The development of nanoscale carriers over the past few decades has made possible the delivery of therapies with the potential to overcome membrane barriers and provide specific, targeted delivery. This review seeks to provide a comprehensive overview of the various aspects of nanoparticle formulation and their applications in improving the delivery efficiency of drugs, specifically antiretroviral therapeutics to the brain to treat HIV.

Nanoparticles for brain-specific drug and genetic material delivery, imaging and diagnosis

The poor access of therapeutic drugs and genetic material into the central nervous system due to the presence of the blood-brain barrier often limits the development of effective noninvasive treatments and diagnoses of neurological disorders. Moreover, the delivery of genetic material into neuronal cells remains a challenge because of the intrinsic difficulty in transfecting this cell type. Nanotechnology has arisen as a promising tool to provide solutions for this problem. This review will cover the different approaches that have been developed to deliver drugs and genetic material efficiently to the central nervous system as well as the main nanomaterials used to image the central nervous system and diagnose its disorders.

Solving the Blood-Brain Barrier Challenge for the Effective Treatment of HIV Replication in the Central Nervous System

Recent decades mark a great progress in the treatment of HIV infection. What was once a deadly disease is now a chronic infection. However, HIV-infected patients are prone to develop comorbidities, which severely affect their daily functions. For example, a large population of patients develop a variety of neurological and cognitive complications, called HIV associated neurological disorders (HAND). Despite efficient repression of viral replication in the periphery, evidence shows that the virus can remain active in the central nervous system (CNS). This low level of replication is believed to result in a progression of neurocognitive dysfunction in infected individuals. Insufficient viral inhibition in the brain results from the inability of several treatment drugs in crossing the blood-brain barrier (BBB) and reaching therapeutic concentrations in the CNS. The current manuscript discusses several strategies that are being developed to enable therapeutics to cross the BBB, including bypassing BBB, inhibition of efflux transporters, the use of active transporters present at the BBB, and nanotechnology. The increased concentration of therapeutics in the CNS is desirable to prevent viral replication; however, potential side effects of anti-retroviral drugs need also to be taken into consideration.

Nanogel-Conjugated Reverse Transcriptase Inhibitors and Their Combinations as Novel Antiviral Agents with Increased Efficacy against HIV-1 Infection

Nucleoside reverse transcriptase inhibitors (NRTIs) are an integral part of the current antiretroviral therapy (ART), which dramatically reduced the mortality from AIDS and turned the disease from lethal to chronic. The further steps in curing the HIV-1 infection must include more effective targeting of infected cells and virus sanctuaries inside the body and modification of drugs and treatment schedules to reduce common complications of the long-term treatment and increase patient compliancy. Here, we describe novel NRTI prodrugs synthesized from cholesteryl-ε-polylysine (CEPL) nanogels by conjugation with NRTI 5'-succinate derivatives (sNRTI). Biodegradability, small particle size, and high NRTI loading (30% by weight) of these conjugates; extended drug release, which would allow a weekly administration schedule; high therapeutic index (>1000) with a lower toxicity compared to NRTIs; and efficient accumulation in macrophages known as carriers for HIV-1 infection are among the most attractive properties of new nanodrugs. Nanogel conjugates of zidovudine (AZT), lamivudine (3TC), and abacavir (ABC) have been investigated individually and in formulations similar to clinical NRTI cocktails. Nanodrug formulations demonstrated 10-fold suppression of reverse transcriptase activity (EC90) in HIV-infected macrophages at 2-10, 2-4, and 1-2 μM drug levels, respectively, for single nanodrugs and dual and triple nanodrug cocktails. Nanogel conjugate of lamivudine was the most effective single nanodrug (EC90 2 μM). Nanodrugs showed a more favorable pharmacokinetics compared to free NRTIs. Infrequent iv injections of PEGylated CEPL-sAZT alone could efficiently suppress HIV-1 RT activity to background level in humanized mouse (hu-PBL) HIV model.

Hazard effects of nanoparticles in central nervous system: Searching for biocompatible nanomaterials for drug delivery

Nanostructured materials are widely used in many applications of industry and biomedical fields. Nanoparticles emerges as potential pharmacological carriers that can be applied in the regenerative medicine, diagnosis and drug delivery. Different types of nanoparticles exhibit ability to cross the brain blood barrier (BBB) and accumulate in several brain areas. Then, efforts have been done to develop safer nanocarrier systems to treat disorders of central nervous system (CNS). However, several in vitro and in vivo studies demonstrated that nanoparticles of different materials exhibit a wide range of neurotoxic effects inducing neuroinflammation and cognitive impairment. For this reason, polymeric nanoparticles arise as a promisor alternative due to their biocompatible and biodegradable properties. After an overview of CNS location and neurotoxic effects of translocated nanoparticles, this review addresses the use of polymeric nanoparticles to the treatment of neuroinfectious diseases, as acquired immunodeficiency syndrome (AIDS) and meningitis.

Nanoneuromedicines for degenerative, inflammatory, and infectious nervous system diseases

Interest in nanoneuromedicine has grown rapidly due to the immediate need for improved biomarkers and therapies for psychiatric, developmental, traumatic, inflammatory, infectious and degenerative nervous system disorders. These, in whole or in part, are a significant societal burden due to growth in numbers of affected people and in disease severity. Lost productivity of the patient and his or her caregiver, and the emotional and financial burden cannot be overstated. The need for improved health care, treatment and diagnostics is immediate. A means to such an end is nanotechnology. Indeed, recent developments of health-care enabling nanotechnologies and nanomedicines range from biomarker discovery including neuroimaging to therapeutic applications for degenerative, inflammatory and infectious disorders of the nervous system. This review focuses on the current and future potential of the field to positively affect clinical outcomes. From the clinical editor: Many nervous system disorders remain unresolved clinical problems. In many cases, drug agents simply cannot cross the blood-brain barrier (BBB) into the nervous system. The advent of nanomedicines can enhance the delivery of biologically active molecules for targeted therapy and imaging. This review focused on the use of nanotechnology for degenerative, inflammatory, and infectious diseases in the nervous system.

Amphiphilic cationic nanogels as brain-targeted carriers for activated nucleoside reverse transcriptase inhibitors

Progress in AIDS treatment shifted emphasis towards limiting adverse effects of antiviral drugs while improving the treatment of hard-to-reach viral reservoirs. Many therapeutic nucleoside reverse transcriptase inhibitors (NRTI) have a limited access to the central nervous system (CNS). Increased NRTI levels induced various complications during the therapy, including neurotoxicity, due to the NRTI toxicity to mitochondria. Here, we describe an innovative design of biodegradable cationic cholesterol-ε-polylysine nanogel carriers for delivery of triphosphorylated NRTIs that demonstrated high anti-HIV activity along with low neurotoxicity, warranting minimal side effects following systemic administration. Efficient CNS targeting was achieved by nanogel modification with brain-specific peptide vectors. Novel dual and triple-drug nanoformulations, analogous to therapeutic NRTI cocktails, displayed equal or higher antiviral activity in HIV-infected macrophages compared to free drugs. Our results suggest potential alternative approach to HIV-1 treatment focused on the effective nanodrug delivery to viral reservoirs in the CNS and reduced neurotoxicity.

Macrophages associated with tumors as potential targets and therapeutic intermediates

Tumor-associated macrophages (TAMs) form approximately 50% of tumor mass. TAMs were shown to promote tumor growth by suppressing immunocompetent cells, inducing neovascularization and supporting cancer stem cells. TAMs retain mobility in tumor mass, which can potentially be employed for better intratumoral biodistribution of nanocarriers and effective tumor growth inhibition. Due to the importance of TAMs, they are increasingly becoming principal targets of novel therapeutic approaches. In this review, we compare features of macrophages and TAMs that are essential for TAM-directed therapies, and illustrate the advantages of nanomedicine that are related to the preferential capture of nanocarriers by Mϕ in the process of drug delivery. We discuss recent efforts in reprogramming or inhibiting tumor-protecting properties of TAMs, and potential strategies to increase efficacy of conventional chemotherapy by combining with macrophage-associated delivery of nanodrugs.

Nanoengineered drug delivery systems for enhancing antibiotic therapy

Formulation scientists are recognizing nanoengineered drug delivery systems as an effective strategy to overcome limitations associated with antibiotic drug therapy. Antibiotics encapsulated into nanodelivery systems will contribute to improved management of patients with various infectious diseases and to overcoming the serious global burden of antibiotic resistance. An extensive review of several antibiotic-loaded nanocarriers that have been formulated to target drugs to infectious sites, achieve controlled drug release profiles, and address formulation challenges, such as low-drug entrapment efficiencies, poor solubility and stability is presented in this paper. The physicochemical properties and the in vitro/in vivo performances of various antibiotic-loaded delivery systems, such as polymeric nanoparticles, micelles, dendrimers, liposomes, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles, nanohybirds, nanofibers/scaffolds, nanosheets, nanoplexes, and nanotubes/horn/rods and nanoemulsions, are highlighted and evaluated. Future studies that will be essential to optimize formulation and commercialization of these antibiotic-loaded nanosystems are also identified. The review presented emphasizes the significant formulation progress achieved and potential that novel nanoengineered antibiotic drug delivery systems have for enhancing the treatment of patients with a range of infections.

Humanized mouse models for HIV-1 infection of the CNS

Since the onset of the HIV epidemic, there has been a shift from a deadly diagnosis to the management of a chronic disease. This shift is the result of the development of highly effective drugs that are able to suppress viral replication for years. The availability of these regimens has also shifted the neurocognitive pathology associated with infection from potentially devastating to a much milder phenotype. As the disease outcome has changed significantly with the availability of antiretroviral therapy, there is an opportunity to re-evaluate the currently available models to address the neurocognitive pathology seen in suppressed patients. In the following, we seek to summarize the current literature on humanized mouse models and their utility in understanding how HIV infection leads to changes in the central nervous system (CNS). Also, we identify some of the unanswered questions regarding HIV infection of the CNS as well as the opportunities and limitations of currently existing models to address those questions. Finally, our conclusions indicate that the earlier humanized models used to study HIV infection in the CNS provided an excellent foundation for the type of work currently being performed using novel humanized mouse models. We also indicate the potential of some humanized mouse models that have not been used as of this time for the analysis of HIV infection in the brain.

Infectious Diseases: Need for Targeted Drug Delivery

Infectious diseases are a leading cause of death worldwide, with the constant fear of global epidemics. It is indeed an irony that the reticuloendothelial system (RES), the body’s major defence system, is the primary site for intracellular infections which are more difficult to treat. Pro-inflammatory M1 macrophages play an important role in defence. However, ingenious pathogen survival mechanisms including phagolysosome destruction enable their persistence. Microbial biofilms present additional challenges. Low intracellular drug concentrations, drug efflux by efflux pumps and/or enzymatic degradation, emergence of multi-drug resistance (MDR), are serious limitations of conventional therapy. Targeted delivery using nanocarriers, and passive and active targeting strategies could provide quantum increase in intracellular drug concentration. Receptor mediated endocytosis using appropriate ligands is a viable approach. Liposomes and polymeric/lipidic nanoparticles, dendrimers micelles and micro/nanoemulsions could all be relied upon. Specialised targeting approaches are demonstrated for important diseases like tuberculosis, HIV and Malaria. Application of targeted delivery in the treatment of veterinary infections is exemplified and future possibilities indicated. The chapter thus provides an overview on important aspects of infectious diseases and the challenges therein, while stressing on the promise of targeted drug delivery in augmenting therapy of infectious diseases.

Nanoparticle-based drug delivery to improve the efficacy of antiretroviral therapy in the central nervous system

Antiretroviral drug therapy plays a cornerstone role in the treatment of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome patients. Despite obvious advances over the past 3 decades, new approaches toward improved management of infected individuals are still required. Drug distribution to the central nervous system (CNS) is required in order to limit and control viral infection, but the presence of natural barrier structures, in particular the blood-brain barrier, strongly limits the perfusion of anti-HIV compounds into this anatomical site. Nanotechnology-based approaches may help providing solutions for antiretroviral drug delivery to the CNS by potentially prolonging systemic drug circulation, increasing the crossing and reducing the efflux of active compounds at the blood-brain barrier, and providing cell/tissue-targeting and intracellular drug delivery. After an initial overview on the basic features of HIV infection of the CNS and barriers to active compound delivery to this anatomical site, this review focuses on recent strategies based on antiretroviral drug-loaded solid nanoparticles and drug nanosuspensions for the potential management of HIV infection of the CNS.