Polyanionic carbosilane dendrimer-conjugated antiviral drugs as efficient microbicides: Recent trends and developments in HIV treatment/therapy

A new class of polyphenolic carbosilane dendrimers binds human serum albumin in a structure-dependent fashion

The use of dendrimers as drug and nucleic acid delivery systems requires knowledge of their interactions with objects on their way to the target. In the present work, we investigated the interaction of a new class of carbosilane dendrimers functionalized with polyphenolic and caffeic acid residues with human serum albumin, which is the most abundant blood protein. The addition of dendrimers to albumin solution decreased the zeta potential of albumin/dendrimer complexes as compared to free albumin, increased density of the fibrillary form of albumin, shifted fluorescence spectrum towards longer wavelengths, induced quenching of tryptophan fluorescence, and decreased ellipticity of circular dichroism resulting from a reduction in the albumin α-helix for random coil structural form. Isothermal titration calorimetry showed that, on average, one molecule of albumin was bound by 6-10 molecules of dendrimers. The zeta size confirmed the binding of the dendrimers to albumin. The interaction of dendrimers and albumin depended on the number of caffeic acid residues and polyethylene glycol modifications in the dendrimer structure. In conclusion, carbosilane polyphenolic dendrimers interact with human albumin changing its structure and electrical properties. However, the consequences of such interaction for the efficacy and side effects of these dendrimers as drug/nucleic acid delivery system requires further research.

Molecular dynamics simulations show how antibodies may rescue HIV-1 mutants incapable of infecting host cells

High mutation and replication rates of HIV-1 result in the continuous generation of variants, allowing it to adapt to changing host environments. Mutations often have deleterious effects, but variants carrying them are rapidly purged. Surprisingly, a particular variant incapable of entering host cells was found to be rescued by host antibodies targeting HIV-1. Understanding the molecular mechanism of this rescue is important to develop and improve antibody-based therapies. To unravel the underlying mechanisms, we performed fully atomistic molecular dynamics simulations of the HIV-1 gp41 trimer responsible for viral entry into host cells, its entry-deficient variant, and its complex with the rescuing antibody. We find that the Q563R mutation, which the entry-deficient variant carries, prevents the native conformation of the gp41 6-helix bundle required for entry and stabilizes an alternative conformation instead. This is the consequence of substantial changes in the secondary structure and interactions between the domains of gp41. Binding of the antibody F240 to gp41 reverses these changes and re-establishes the native conformation, resulting in rescue. To test the generality of this mechanism, we performed simulations with the entry-deficient L565A variant and antibody 3D6. We find that 3D6 binding was able to reverse structural and interaction changes introduced by the mutation and restore the native gp41 conformation. Viral variants may not only escape antibodies but be aided by them in their survival, potentially compromising antibody-based therapies, including vaccination and passive immunization. Our simulation framework could serve as a tool to assess the likelihood of such resistance against specific antibodies.Communicated by Ramaswamy H. SarmaCommunicated by Ramaswamy H. Sarma.

Dendrimer: An update on recent developments and future opportunities for the brain tumors diagnosis and treatment

A brain tumor is an uncontrolled cell proliferation, a mass of tissue composed of cells that grow and divide abnormally and appear to be uncontrollable by the processes that normally control normal cells. Approximately 25,690 primary malignant brain tumors are discovered each year, 70% of which originate in glial cells. It has been observed that the blood-brain barrier (BBB) limits the distribution of drugs into the tumour environment, which complicates the oncological therapy of malignant brain tumours. Numerous studies have found that nanocarriers have demonstrated significant therapeutic efficacy in brain diseases. This review, based on a non-systematic search of the existing literature, provides an update on the existing knowledge of the types of dendrimers, synthesis methods, and mechanisms of action in relation to brain tumours. It also discusses the use of dendrimers in the diagnosis and treatment of brain tumours and the future possibilities of dendrimers. Dendrimers are of particular interest in the diagnosis and treatment of brain tumours because they can transport biochemical agents across the BBB to the tumour and into the brain after systemic administration. Dendrimers are being used to develop novel therapeutics such as prolonged release of drugs, immunotherapy, and antineoplastic effects. The use of PAMAM, PPI, PLL and surface engineered dendrimers has proven revolutionary in the effective diagnosis and treatment of brain tumours.

Carbosilane dendritic nanostructures, highly versatile platforms for pharmaceutical applications

Dendrimers are multifunctional molecules with well-defined size and structure due to the step-by-step synthetic procedures required in their preparation. Dendritic constructs based on carbosilane scaffolds present carbon-carbon and carbon-silicon bonds, which results in stable, lipophilic, inert, and flexible structures. These properties are highly appreciated in different areas, including the pharmaceutical field, as they can increase the interaction with cell membranes and improve the therapeutic action. This article summarizes the most recent advances in the pharmaceutical applications of carbosilane dendritic molecules, from therapeutics to diagnostics and prevention tools. Dendrimers decorated with cationic, anionic, or other moieties, including metallodendrimers; supramolecular assemblies; dendronized nanoparticles and surfaces; as well as dendritic networks like hydrogels are described. The collected examples confirm the potential of carbosilane dendrimers and dendritic materials as antiviral or antibacterial agents; in therapy against cancer, neurodegenerative disease, or oxidative stress; or many other biomedical applications. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Baseline and time-updated factors in preclinical development of anionic dendrimers as successful anti-HIV-1 vaginal microbicides

Although a wide variety of topical microbicides provide promising in vitro and in vivo efficacy, most of them failed to prevent sexual transmission of human immunodeficiency virus type 1 (HIV‐1) in human clinical trials. In vitro, ex vivo, and in vivo models must be optimized, considering the knowledge acquired from unsuccessful and successful clinical trials to improve the current gaps and the preclinical development protocols. To date, dendrimers are the only nanotool that has advanced to human clinical trials as topical microbicides to prevent HIV‐1 transmission. This fact demonstrates the importance and the potential of these molecules as microbicides. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV‐1 that disturb HIV‐1 entry. Herein, the most significant advancements in topical microbicide development, trying to mimic the real‐life conditions as closely as possible, are discussed. This review also provides the preclinical assays that anionic dendrimers have passed as microbicides because they can improve current antiviral treatments' efficacy.

This article is categorized under:

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease

Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine

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.

Clinical diagonal translation of nanoparticles: Case studies in dendrimer nanomedicine

Among the numerous nanomedicine formulations, dendrimers have emerged as original, efficient, carefully assembled, hyperbranched, polymeric nanoparticles based on synthetic monomers. Dendrimers are used either as nanocarriers of drugs or as drugs themselves. When used as drug carriers, dendrimers are considered 'best-in-class agents', modifying and enhancing the pharmacokinetic and pharmacodynamic properties of the active entities encapsulated or conjugated with the dendrimers. When used as drugs themselves, dendrimers represent a novel category of "first-in-class" drugs. The purpose of this original review is to analyse the different strategies involved in the development, application, and impact of dendrimers as drugs. We examine a selection of nanoparticles that use multifunctional elements and demonstrate clinical multifunctionality, and we extend these principles to applications in dendrimer nanomedicine design. Finally, for practical consideration, the concepts of vertical and diagonal translation are introduced as potential strategies to facilitate dendrimer development.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

First-in-class and best-in-class dendrimer nanoplatforms from concept to clinic: Lessons learned moving forward

Research to develop active dendrimers by themselves or as nanocarriers represents a promising approach to discover new biologically active entities that can be used to tackle unmet medical needs including difficult diseases. These developments are possible due to the exceptional physicochemical properties of dendrimers, including their biocompatibility, as well as their therapeutic activity as nanocarriers and drugs themselves. Despite a large number of academic studies, very few dendrimers have crossed the 'valley of death' between. Only a few number of pharmaceutical companies have succeeded in this way. In fact, only Starpharma (Australia) and Orpheris, Inc. (USA), an Ashvattha Therapeutics subsidiary, can fill all the clinic requirements to have in the market dendrimers based drugs/nancocarriers. After evaluating the main physicochemical properties related to the respective biological activity of dendrimers classified as first-in-class or best-in-class in nanomedicine, this original review analyzes the advantages and disavantages of these two strategies as well the concerns to step in clinical phases. Various solutions are proposed to advance the use of dendrimers in human health.

Applications of Nanoparticles for Herpes Simplex Virus (HSV) and Human Immunodeficiency Virus (HIV) Treatment

In recent years, the growing studies focused on the immunotherapy of hepatocellular carcinoma and proved the preclinical and clinical promises of host antitumor immune response. However, there were still various obstacles in meeting satisfactory clinic need, such as low response rate, primary resistance and secondary resistance to immunotherapy. Tackling these barriers required a deeper understanding of immune underpinnings and a broader understanding of advanced technology. This review described immune microenvironment of liver and HCC which naturally decided the complexity of immunotherapy, and summarized recent immunotherapy focusing on different points. The ever-growing clues indicated that the instant killing of tumor cell and the subsequent relive of immunosuppressive microenvironment were both indis- pensables. The nanotechnology applied in immunotherapy and the combination with intervention technology was also discussed.

Nanotechnology-based antiviral therapeutics

The host immune system is highly compromised in case of viral infections and relapses are very common. The capacity of the virus to destroy the host cell by liberating its own DNA or RNA and replicating inside the host cell poses challenges in the development of antiviral therapeutics. In recent years, many new technologies have been explored for diagnosis, prevention, and treatment of viral infections. Nanotechnology has emerged as one of the most promising technologies on account of its ability to deal with viral diseases in an effective manner, addressing the limitations of traditional antiviral medicines. It has not only helped us to overcome problems related to solubility and toxicity of drugs, but also imparted unique properties to drugs, which in turn has increased their potency and selectivity toward viral cells against the host cells. The initial part of the paper focuses on some important proteins of influenza, Ebola, HIV, herpes, Zika, dengue, and corona virus and those of the host cells important for their entry and replication into the host cells. This is followed by different types of nanomaterials which have served as delivery vehicles for the antiviral drugs. It includes various lipid-based, polymer-based, lipid-polymer hybrid-based, carbon-based, inorganic metal-based, surface-modified, and stimuli-sensitive nanomaterials and their application in antiviral therapeutics. The authors also highlight newer promising treatment approaches like nanotraps, nanorobots, nanobubbles, nanofibers, nanodiamonds, nanovaccines, and mathematical modeling for the future. The paper has been updated with the recent developments in nanotechnology-based approaches in view of the ongoing pandemic of COVID-19.Graphical abstract.

Application of Dendrimers for Treating Parasitic Diseases

Despite advances in medical knowledge, parasitic diseases remain a significant global health burden and their pharmacological treatment is often hampered by drug toxicity. Therefore, drug delivery systems may provide useful advantages when used in combination with conventional therapeutic compounds. Dendrimers are three-dimensional polymeric structures, characterized by a central core, branches and terminal functional groups. These nanostructures are known for their defined structure, great water solubility, biocompatibility and high encapsulation ability against a wide range of molecules. Furthermore, the high ratio between terminal groups and molecular volume render them a hopeful vector for drug delivery. These nanostructures offer several advantages compared to conventional drugs for the treatment of parasitic infection. Dendrimers deliver drugs to target sites with reduced dosage, solving side effects that occur with accepted marketed drugs. In recent years, extensive progress has been made towards the use of dendrimers for therapeutic, prophylactic and diagnostic purposes for the management of parasitic infections. The present review highlights the potential of several dendrimers in the management of parasitic diseases.

Sulfoglycodendrimer Therapeutics for HIV-1 and SARS-CoV-2

Hexavalent sulfoglycodendrimers (SGDs) are synthesized as mimics of host cell heparan sulfate proteoglycans (HSPGs) to inhibit the early stages in viral binding/entry of HIV‐1 and SARS‐CoV‐2. Using an HIV neutralization assay, the most promising of the seven candidates are found to have sub‐micromolar anti‐HIV activities. Molecular dynamics simulations are separately implemented to investigate how/where the SGDs interacted with both pathogens. The simulations revealed that the SGDs: 1) develop multivalent binding with polybasic regions within and outside of the V3 loop on glycoprotein 120 (gp120) for HIV‐1, and consecutively bind with multiple gp120 subunits, and 2) interact with basic amino acids in both the angiotensin‐converting enzyme 2 (ACE2) and HSPG binding regions of the Receptor Binding Domain (RBD) from SARS‐CoV‐2. These results illustrate the considerable potential of SGDs as inhibitors in viral binding/entry of both HIV‐1 and SARS‐CoV‐2 pathogens, leading the way for further development of this class of molecules as broad‐spectrum antiviral agents.

Peptides and Dendrimers: How to Combat Viral and Bacterial Infections

The alarming growth of antimicrobial resistance and recent viral pandemic events have enhanced the need for novel approaches through innovative agents that are mainly able to attach to the external layers of bacteria and viruses, causing permanent damage. Antimicrobial molecules are potent broad-spectrum agents with a high potential as novel therapeutics. In this context, antimicrobial peptides, cell penetrating peptides, and antiviral peptides play a major role, and have been suggested as promising solutions. Furthermore, dendrimers are to be considered as suitable macromolecules for the development of advanced nanosystems that are able to complement the typical properties of dendrimers with those of peptides. This review focuses on the description of nanoplatforms constructed with peptides and dendrimers, and their applications.

Emergence of Nanotechnology to Fight HIV Sexual Transmission: The Trip of G2-S16 Polyanionic Carbosilane Dendrimer to Possible Pre-Clinical Trials

Development of new, safe, and effective microbicides to prevent human immunodeficiency virus HIV sexual transmission is needed. Unfortunately, most microbicides proved ineffective to prevent the risk of HIV-infection in clinical trials. We are working with G2-S16 polyanionic carbosilane dendrimer (PCD) as a new possible vaginal topical microbicide, based on its short reaction times, wide availability, high reproducibility, and quantitative yields of reaction. G2-S16 PCD exerts anti-HIV activity at an early stage of viral replication, by blocking gp120/CD4/CCR5 interaction, and providing a barrier against infection for long periods of time. G2-S16 PCD was stable at different pH values, as well as in the presence of seminal fluids. It maintained the anti-HIV activity against R5/X4 HIV over time, did not generate any type of drug resistance, and retained the anti-HIV effect when exposed to semen-enhanced viral infection. Importantly, G2-S16 PCD did not modify vaginal microbiota neither in vitro or in vivo. Histopathological examination did not show vaginal irritation, inflammation, lesions, or damage in the vaginal mucosa, after administration of G2-S16 PCD at different concentrations and times in female mice and rabbit animal models. Based on these promising data, G2-S16 PCD could become a good, safe, and readily available candidate to use as a topical vaginal microbicide against HIV.

Dendritic Nanotheranostic for the Delivery of Infliximab: A Potential Carrier in Rheumatoid Arthritis Therapy

Antibodies are macromolecules that specifically recognize their target, making them good candidates to be employed in various therapies. The possibility of attaching a drug to an immunoglobulin makes it possible to release it specifically into the affected tissue as long as it overexpresses the target. However, chemical coupling could affect the functionality (specificity and affinity) of the antibody. It has been observed that the use of intermediaries, such as dendrimers, could resolve this issue. Because carbosilane dendrimers have aroused great interest in the field of biomedicine, this report describes the synthesis of an anionic carbosilane dendrimer with a fluorochrome on its surface that then forms a conjugate with an antibody. It has been used as immunoglobulin and infliximab, whose target is TNF-α, which is a cytokine that is overexpressed in the inflamed area or even in the blood of patients with autoimmune diseases, such as rheumatoid arthritis. In addition, the integrity and functionality of the antibody has been studied to see if they have been affected after the chemical coupling process.

Novel Applications of Nanotechnology in Controlling HIV and HSV Infections

Infectious diseases have been prevalent since many decades and viral pathogens have caused global health crisis and economic meltdown on a devastating scale. High occurrence of newer viral infections in the recent years, in spite of the progress achieved in the field of pharmaceutical sciences defines the critical need for newer and more effective antiviral therapies and diagnostics. The incidence of multi-drug resistance and adverse effects due to the prolonged use of anti-viral therapy is also a major concern. Nanotechnology offers a cutting edge platform for the development of novel compounds and formulations for biomedical applications. The unique properties of nano-based materials can be attributed to the multi-fold increase in the surface to volume ratio at the nano-scale, tunable surface properties of charge and chemical moieties. Idealistic pharmaceutical properties such as increased bioavailability and retention times, lower toxicity profiles, sustained release formulations, lower dosage forms and most importantly, targeted drug delivery can be achieved through the approach of nanotechnology. The extensively researched nano-based materials are metal and polymeric nanoparticles, dendrimers and micelles, nano-drug delivery vesicles, liposomes and lipid based nanoparticles. In this review article, the impact of nanotechnology on the treatment of Human Immunodeficiency Virus (HIV) and Herpes Simplex Virus (HSV) viral infections during the last decade are outlined.

Applications and Limitations of Dendrimers in Biomedicine

Biomedicine represents one of the main study areas for dendrimers, which have proven to be valuable both in diagnostics and therapy, due to their capacity for improving solubility, absorption, bioavailability and targeted distribution. Molecular cytotoxicity constitutes a limiting characteristic, especially for cationic and higher-generation dendrimers. Antineoplastic research of dendrimers has been widely developed, and several types of poly(amidoamine) and poly(propylene imine) dendrimer complexes with doxorubicin, paclitaxel, imatinib, sunitinib, cisplatin, melphalan and methotrexate have shown an improvement in comparison with the drug molecule alone. The anti-inflammatory therapy focused on dendrimer complexes of ibuprofen, indomethacin, piroxicam, ketoprofen and diflunisal. In the context of the development of antibiotic-resistant bacterial strains, dendrimer complexes of fluoroquinolones, macrolides, beta-lactamines and aminoglycosides have shown promising effects. Regarding antiviral therapy, studies have been performed to develop dendrimer conjugates with tenofovir, maraviroc, zidovudine, oseltamivir and acyclovir, among others. Furthermore, cardiovascular therapy has strongly addressed dendrimers. Employed in imaging diagnostics, dendrimers reduce the dosage required to obtain images, thus improving the efficiency of radioisotopes. Dendrimers are macromolecular structures with multiple advantages that can suffer modifications depending on the chemical nature of the drug that has to be transported. The results obtained so far encourage the pursuit of new studies.

Dendrimer-Based Drug Delivery Systems for Brain Targeting

Human neuroscience has made remarkable progress in understanding basic aspects of functional organization; it is a renowned fact that the blood-brain barrier (BBB) impedes the permeation and access of most drugs to central nervous system (CNS) and that many neurological diseases remain undertreated. Therefore, a number of nanocarriers have been designed over the past few decades to deliver drugs to the brain. Among these nanomaterials, dendrimers have procured an enormous attention from scholars because of their nanoscale uniform size, ease of multi-functionalization, and available internal cavities. As hyper-branched 3D macromolecules, dendrimers can be maneuvered to transport diverse therapeutic agents, incorporating small molecules, peptides, and genes; diminishing their cytotoxicity; and improving their efficacy. Herein, the present review will give exhaustive details of extensive researches in the field of dendrimer-based vehicles to deliver drugs through the BBB in a secure and effectual manner. It is also a souvenir in commemorating Donald A. Tomalia on his 80th birthday.

Combination of G2-S16 dendrimer/dapivirine antiretroviral as a new HIV-1 microbicide

Aim: To research the synergistic activity of G2-S16 dendrimer and dapivirine (DPV) antiretroviral as microbicide candidate to prevent HIV-1 infection. Materials & methods: We assess the toxicity of DPV on cell lines by MTT assay, the anti-HIV-1 activity of G2-S16 and DPV alone or combined at several fixed ratios. Finally, their ability to inhibit the bacterial growth in vitro was assayed. The analysis of combinatorial effects and the effective concentrations were performed with CalcuSyn software. Conclusion: Our results represent the first proof-of-concept study of G2-S16/DPV combination to develop a safe microbicide.

Reverse Transcriptase Inhibitors Nanosystems Designed for Drug Stability and Controlled Delivery

An in-depth analysis of nanotechnology applications for the improvement of solubility, distribution, bioavailability and stability of reverse transcriptase inhibitors is reported. Current clinically used nucleoside and non-nucleoside agents, included in combination therapies, were examined in the present survey, as drugs belonging to these classes are the major component of highly active antiretroviral treatments. The inclusion of such agents into supramolecular vesicular systems, such as liposomes, niosomes and lipid solid NPs, overcomes several drawbacks related to the action of these drugs, including drug instability and unfavorable pharmacokinetics. Overall results reported in the literature show that the performances of these drugs could be significantly improved by inclusion into nanosystems.

Poly(N-vinylcaprolactam) Nanogels with Antiviral Behavior against HIV-1 Infection

Stimuli-responsive nanogels offer promising perspectives for the development of next generation formulations for biomedical applications. In this work, poly(N-vinylcaprolactam) nanogels were synthesized varying the concentration of monomer and crosslinking agent. Thus, the inhibitory effect of poly(N-vinylcaprolactam) nanogels against HIV-1 infection is presented for the first time. In particular, we have demonstrated that one of the synthesized poly(N-vinylcaprolactam) nanogels with initial concentration of 80 mg of vinylcaprolactam and 4% of crosslinking agent shows antiviral behavior against HIV-1 infection since this nanogel inhibits the viral replication in TZM.bl target cells.

Polymeric therapeutic delivery systems for the treatment of infectious diseases

Infectious diseases caused by germs, parasites, fungi, virus and bacteria are one of the leading causes of death worldwide. Polymeric therapeutics are nanomedicines that offer several advantages making them useful for the treatment of infectious diseases such as targeted drug release mechanism, ability to maintain the drug concentration within a therapeutic window for a desired duration, biocompatibility with low immunogenicity and reduced drug toxicity resulting in enhanced therapeutic efficacy of the incorporated drug. Although polymeric therapeutics have been evaluated for the treatment of infectious diseases in vitro and in vivo with improved therapeutic efficacy, most treatments for infectious disease have not been evaluated using polymeric therapeutics. This review will focus on the applications of polymeric therapeutics for the treatment of infectious diseases (preclinical studies and clinical trials), with particular focus on parasitic and viral infections.

Anionic Carbosilane Dendrimers Destabilize the GP120-CD4 Complex Blocking HIV-1 Entry and Cell to Cell Fusion

Cell-to-cell transmission is the most effective pathway for the spread of human immunodeficiency virus (HIV-1). Infected cells expose virus-encoded fusion proteins on their surface as a consequence of HIV-1 replicative cycle that interacts with noninfected cells through CD4 receptor and CXCR4 coreceptor leading to the formation of giant multinucleated cells known as syncytia. Our group previously described the potent activity of dendrimers against CCR5-tropic viruses. Nevertheless, the study of G1-S4, G2-S16, and G3-S16 dendrimers in the context of X4-HIV-1 tropic cell-cell fusion referred to syncytium formation remains still unknown. These dendrimers showed a suitable biocompatibility in all cell lines studied and our results demonstrated that anionic carbosilane dendrimers G1-S4, G2-S16, and G3-S16 significantly inhibit the X4-HIV-1 infection, as well as syncytia formation, in a dose dependent manner. We also demonstrated that G2-S16 and G1-S4 significantly reduced syncytia formation in HIV-1 Env-mediated cell-to-cell fusion model. Molecular modeling and in silico models showed that G2-S16 dendrimer interfered with gp120-CD4 complex and demonstrated its potential use for a treatment.

Recent progress in dendrimer-based nanomedicine development

Dendrimers offer well-defined nanoarchitectures with spherical shape, high degree of molecular uniformity, and multiple surface functionalities. Such unique structural properties of dendrimers have created many applications for drug and gene delivery, nanomedicine, diagnostics, and biomedical engineering. Dendrimers are not only capable of delivering drugs or diagnostic agents to desired sites by encapsulating or conjugating them to the periphery, but also have therapeutic efficacy in their own. When compared to traditional polymers for drug delivery, dendrimers have distinct advantages, such as high drug-loading capacity at the surface terminal for conjugation or interior space for encapsulation, size control with well-defined numbers of peripheries, and multivalency for conjugation to drugs, targeting moieties, molecular sensors, and biopolymers. This review focuses on recent applications of dendrimers for the development of dendrimer-based nanomedicines for cancer, inflammation, and viral infection. Although dendrimer-based nanomedicines still face some challenges including scale-up production and well-characterization, several dendrimer-based drug candidates are expected to enter clinical development phase in the near future.

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

Various strategies (single & multi-pot) to synthesize dendrimer-coated metal nanoparticles and their exploration in various biomedical applications.

Macromolecular Antiviral Agents against Zika, Ebola, SARS, and Other Pathogenic Viruses

Viral pathogens continue to constitute a heavy burden on healthcare and socioeconomic systems. Efforts to create antiviral drugs repeatedly lag behind the advent of pathogens and growing understanding is that broad‐spectrum antiviral agents will make strongest impact in future antiviral efforts. This work performs selection of synthetic polymers as novel broadly active agents and demonstrates activity of these polymers against Zika, Ebola, Lassa, Lyssa, Rabies, Marburg, Ebola, influenza, herpes simplex, and human immunodeficiency viruses. Results presented herein offer structure–activity relationships for these pathogens in terms of their susceptibility to inhibition by polymers, and for polymers in terms of their anionic charge and hydrophobicity that make up broad‐spectrum antiviral agents. The identified leads cannot be predicted based on prior data on polymer‐based antivirals and represent promising candidates for further development as preventive microbicides.

Carbosilane dendrons with fatty acids at the core as a new potential microbicide against HSV-2/HIV-1 co-infection

Herpes simplex virus type 2 (HSV-2) and human immunodeficiency virus type 1 (HIV-1) represent the two most frequent sexually transmitted infections (STI) worldwide. Epidemiological studies suggest that HSV-2 increases the risk of HIV-1 acquisition approximately 3-fold mainly due to the clinical and immunological manifestations. In the absence of vaccines against both STI, the development of new preventive strategies has become essential for further studies. We performed the screening of six novel polyanionic carbosilane dendrons to elucidate their potential activity against HSV-2/HIV-1 co-infection and their mechanism of action. These new nanoparticles are carbosilane branched dendrons from first to third generation, with palmitic or hexanoic fatty acids as the core and capped with sulfonate groups, named G1_d-STE2Hx, G2_d-STE4Hx, G3_d-STE8Hx, G1_d-STE2Pm, G2_d-STE4Pm and G3_d-STE8Pm. G3_d-STE8Hx and G3_d-STE8Pm carbosilane branched dendrons showed high viability. These dendrons also showed a great broad-spectrum antiviral activity, as well as a suitable efficacy against HIV-1 even if the mucosal disruption occurs as a consequence of HSV-2 infection. Our results exert high inhibition against HSV-2 and HIV-1 by blocking the entry of both viruses with the median effective concentration EC₅₀ values in the nanomolar range. Additionally, G3_d-STE8Hx and G3_d-STE8Pm retained their anti-HSV-2/HIV-1 activity at different pH values. G3_d-STE8Hx and G3_d-STE8Pm dendrons may be potential candidates as dual-acting microbicides against HSV-2/HIV-1 co-infection.

Function Oriented Molecular Design: Dendrimers as Novel Antimicrobials

In recent years innovative nanostructures are attracting increasing interest and, among them, dendrimers have shown several fields of application. Dendrimers can be designed and modified in plentiful ways giving rise to hundreds of different molecules with specific characteristics and functionalities. Biomedicine is probably the field where these molecules find extraordinary applicability, and this is probably due to their multi-valency and to the fact that several other chemicals can be coupled to them to obtain desired compounds. In this review we will describe the different production strategies and the tools and technologies for the study of their characteristics. Finally, we provide a panoramic overview of their applications to meet biomedical needs, especially their use as novel antimicrobials.

Docking field-based QSAR and pharmacophore studies on the substituted pyrimidine derivatives targeting HIV-1 reverse transcriptase

HIV-1 reverse transcriptase (RT) is one of the most important enzymes required for viral replication, thus acting as an attractive target for antiretroviral therapy. Pyrimidine analogues reportedly have selective inhibition on HIV-1 RT with favorable antiviral activities in our previous study. To further explore the relationship between inhibitory activity and pharmacophoric characteristics, field-based QSAR models were generated and validated using Schrodinger Suite (correlation coefficient of .8078, cross-validated value of 0.5397 for training set and Q² of 0.4669, Pearson's r of .7357 for test set). Docking, pocket surfaces, and pharmacophore study were also investigated to define the binding pattern and pharmacophoric features, including (i) π-π interaction with residue Tyr181, Tyr188, and Trp229 and p-π interaction with His235 and (ii) hydrogen bond with residue Lys101 and halogen bond with residue Tyr188. The pharmacophore features of six-point hypothesis AADRRR.184, AAADRR.38, and AADRRR.26 further complimented to the docking and QSAR results. We also found that the protein-ligand complex exhibited high relative binding free energy. These observations could be potentially utilized to guide the rational design and optimization of novel HIV-1 RT inhibitors.

New anionic carbosilane dendrons functionalized with a DO3A ligand at the focal point for the prevention of HIV-1 infection

Novel third-generation polyanionic carbosilane dendrons with sulfonate or carboxylate end-groups and functionalized with a DO3A ligand at the focal point, and their corresponding copper complexes, have been prepared as antiviral compounds to prevent HIV-1 infection. The topology enables the compound to have an excellent chelating agent, DO3A, while keeping anionic peripheral groups for a therapeutic action. In this study, the cytotoxicity and anti-HIV-1 abilities of carboxylate- (5) or sulfonate-terminated (6) dendrons containing DO3A and their copper complexes (7 or 8) were evaluated. All compounds showed low cytotoxicity and demonstrated potent and broad-spectrum anti-HIV-1 activity in vitro. We also assessed the mode of antiviral action on the inhibition of HIV-1 through a panel of different in vitro antiviral assays. Our results show that copper-free dendron 6 protects the epithelial monolayer from short-term cell disruption. Copper-free dendrons 5 and 6 exert anti-HIV-1 activity at an early stage of the HIV-1 lifecycle by binding to the envelope glycoproteins of HIV-1 and by interacting with the CD4 cell receptor and blocking the binding of gp120 to CD4, and consequently HIV-1 entry. These findings show that copper-free dendrons 5 and 6 have a high potency against HIV-1 infection, confirming their non-specific ability and suggesting that these compounds deserve further study as potential candidate microbicides to prevent HIV-1 transmission.

G2-S16 dendrimer as a candidate for a microbicide to prevent HIV-1 infection in women

Unprotected heterosexual intercourse is the first route for sustaining the global spread of human immunodeficiency virus type 1 (HIV-1), being responsible for 80% of new HIV-1 infections in the world. The presence of inflammation in the female reproductive tract and the presence of semen increases the risk of heterosexual HIV-1 transmission. This state-of-the-art research based on an innovative nanotechnology design was focused on a toxicological study of the limitation of the activity of the novel H₂O-soluble anionic carbosilane dendrimer G2-S16 in the adult cervical and foreskin epithelia. The G2-S16 dendrimer did not cause any irritation or inflammation in the vaginal epithelium, proving that this dendrimer is a safe nanocompound for vaginal application to control viral transmission. It was shown that no significant differences were found in mortality, sublethal or teratogenic effects when the zebra fish embryos were treated with G2-S16. In short, G2-S16 seems to be an ideal candidate for the development of a topical microbicide against HIV-1 infection and the next step is try in clinical trials, because of its great in vivo biocompatibility, as well as its ability to halt HIV-1 infection in the presence of semen.

Efficacy of carbosilane dendrimers with an antiretroviral combination against HIV-1 in the presence of semen-derived enhancer of viral infection

Amyloid fibrils, which are present in semen, were considered to be a cause of topical vaginal gel ineffectiveness in vivo after microbicides failed as HIV-1 prophylaxis. Therefore, it was necessary to determine whether a dendrimer was suitable for further evaluation in an in vitro model of semen-enhanced viral infection (SEVI). We demonstrated that SEVI in TZM.bl cell cultures increased the infectivity of R5-HIV-1_NL(AD8), pTHRO.c and pCH058.c isolates, causing higher IC₅₀ values for two polyanionic carbosilane dendrimers, G2-STE16 and G3-S16. However, both dendrimers maintained protection rates of 90% at non-toxic concentrations. When dendrimers were combined with Tenofovir/Maraviroc (TDF/MVC), the anti-HIV-1 effect remained at a minimum IC₅₀ increase between 1- and 7-fold in the presence of amyloid fibrils. In peripheral blood mononuclear cells (PBMC), IC₅₀ values were slightly influenced by the presence of semen. In brief, dendrimers combined with antiretrovirals showed a synergistic effect. This result plays a crucial role in new microbicide formulations, as it overcomes the negative effects of amyloid fibrils.

Application of nanotechnology for the development of microbicides

The vaginal route is increasingly being considered for both local and systemic delivery of drugs, especially those unsuitable for oral administration. One of the opportunities offered by this route but yet to be fully utilised is the administration of microbicides. Microbicides have an unprecedented potential for mitigating the global burden from HIV infection as heterosexual contact accounts for most of the new infections occurring in sub-Saharan Africa, the region with the highest prevalent rates. Decades of efforts and massive investment of resources into developing an ideal microbicide have resulted in disappointing outcomes, as attested by several clinical trials assessing the suitability of those formulated so far. The highly complex and multi-level biochemical interactions that must occur among the virus, host cells and the drug for transmission to be halted means that a less sophisticated approach to formulating a microbicide e.g. conventional gels, etc may have to give way for a different formulation approach. Nanotechnology has been identified to offer prospects for fabricating structures with high capability of disrupting HIV transmission. In this review, predominant challenges seen in microbicide development have been highlighted and possible ways of surmounting them suggested. Furthermore, formulations utilising some of these highly promising nanostructures such as liposomes, nanofibres and nanoparticles have been discussed. A perspective on how a tripartite collaboration among governments and their agencies, the pharmaceutical industry and academic scientists to facilitate the development of an ideal microbicide in a timely manner has also been briefly deliberated.

Polyanionic carbosilane dendrimers prevent hepatitis C virus infection in cell culture

Hepatitis C virus (HCV) infection is a major biomedical problem worldwide. Although new direct antiviral agents (DAAs) have been developed for the treatment of chronic HCV infection, the potential emergence of resistant virus variants and the difficulties to implement their administration worldwide make the development of novel antiviral agents an urgent need. Moreover, no effective vaccine is available against HCV and transmission of the virus still occurs particularly when prophylactic measures are not taken. We used a cell-based system to screen a battery of polyanionic carbosilane dendrimers (PCDs) to identify compounds with antiviral activity against HCV and show that they inhibit effective virus adsorption of major HCV genotypes. Interestingly, one of the PCDs irreversibly destabilized infectious virions. This compound displays additive effect in combination with a clinically relevant DAA, sofosbuvir. Our results support further characterization of these molecules as nanotools for the control of hepatitis C virus spread.

Mechanistic Studies of Viral Entry: An Overview of Dendrimer-Based Microbicides As Entry Inhibitors Against Both HIV and HSV-2 Overlapped Infections

This review provides an overview of the development of different dendrimers, mainly polyanionic, against human immunodeficiency virus (HIV) and genital herpes (HSV-2) as topical microbicides targeting the viral entry process. Vaginal topical microbicides to prevent sexually transmitted infections such as HIV and HSV-2 are urgently needed. To inhibit HIV/HSV-2 entry processes, new preventive targets have been established to maximize the current therapies against wild-type and drug-resistant viruses. The entry of HIV/HSV-2 into target cells is a multistep process that triggers a cascade of molecular interactions between viral envelope proteins and cell surface receptors. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV/HSV-2. Inhibitors of each entry step have been identified with regard to generations and surface groups, and possible roles for these agents in anti-HIV/HSV-2 therapies have also been discussed. Four potential binding sites for impeding HIV infection (HSPG, DC-SIGN, GSL, and CD4/gp120 inhibitors) and HSV-2 infection (HS, gB, gD, and gH/gL inhibitors) exist according to their mechanisms of action and structures. This review clarifies that inhibition of HIV/HSV-2 entry continues to be a promising target for drug development because nanotechnology can transform the field of HIV/HSV-2 prevention by improving the efficacy of the currently available antiviral treatments.

Efficacy of HIV antiviral polyanionic carbosilane dendrimer G2-S16 in the presence of semen

The development of a safe and effective microbicide to prevent the sexual transmission of human immunodeficiency virus (HIV)-1 is urgently needed. Unfortunately, the majority of microbicides, such as poly(L-lysine)-dendrimers, anionic polymers, or antiretrovirals, have proved inactive or even increased the risk of HIV infection in clinical trials, most probably due to the fact that these compounds failed to prevent semen-exposed HIV infection. We showed that G2-S16 dendrimer exerts anti-HIV-1 activity at an early stage of viral replication, blocking the gp120/CD4/CCR5 interaction and providing a barrier to infection for long periods, confirming its multifactorial and nonspecific ability. Previously, we demonstrated that topical administration of G2-S16 prevents HIV transmission in humanized BLT mice without irritation or vaginal lesions. Here, we demonstrated that G2-S16 is active against mock- and semen-exposed HIV-1 and could be a promising microbicide against HIV infection.

Synthesis and anticancer activity of carbosilane metallodendrimers based on arene ruthenium(ii) complexes

A series of new organometallic carbosilane dendrimers (first and second generation) and the corresponding non-dendritic mononuclear based on ruthenium arene fragments are described. The metallodendrimers were prepared by reactions of the precursor [Ru(η(6)-p-cymene)Cl2]2 with carbosilane dendrimers functionalized with N-donor monodentate ligands such as NH2- and pyridine, or with N,O-, N,N-chelating imine ligands. While the dendrimer precursors are insoluble in DMSO or water, novel metallodendrimers are soluble in DMSO and some of them are even highly soluble in water. The molecular structure of the "Ru-NH2" mononuclear compound (zero generation) was determined by single-crystal X-ray crystallography. The cytotoxicity activity of these dendritic structures was evaluated in several human cancer cell lines and compared with that of the corresponding mononuclear ruthenium complexes. Most compounds display significant cytotoxic activities in the low micromolar range with the first generation ruthenium dendrimers being the most active compounds. The cell death type for selected compounds has been studied as well as their reactivity towards relevant biomolecules such as DNA, Human Serum Albumin (HSA) and Cathepsin-B. All the data point to a mode of action different from that of cisplatin for most complexes. First generation ruthenium dendrimers inhibit Cathepsin-B, which may suggest potential antimetastatic properties of these compounds.

Dendrimeric based microbicides against sexual transmitted infections associated to heparan sulfate

Cell surface heparan sulfate (HS) represents a common link that many sexually transmitted infections (STIs) require for infection.

The SPL7013 dendrimer destabilizes the HIV-1 gp120-CD4 complex

The poly (l-lysine)-based SPL7013 dendrimer with naphthalene disulphonate surface groups blocks the entry of HIV-1 into target cells and is in clinical trials for development as a topical microbicide. Its mechanism of action against R5 HIV-1, the HIV-1 variant implicated in transmission across individuals, remains poorly understood. Using docking and fully atomistic MD simulations, we find that SPL7013 binds tightly to R5 gp120 in the gp120-CD4 complex but weakly to gp120 alone. Further, the binding, although to multiple regions of gp120, does not occlude the CD4 binding site on gp120, suggesting that SPL7013 does not prevent the binding of R5 gp120 to CD4. Using MD simulations to compute binding energies of several docked structures, we find that SPL7013 binding to gp120 significantly weakens the gp120-CD4 complex. Finally, we use steered molecular dynamics (SMD) to study the kinetics of the dissociation of the gp120-CD4 complex in the absence of the dendrimer and with the dendrimer bound in each of the several stable configurations to gp120. We find that SPL7013 significantly lowers the force required to rupture the gp120-CD4 complex and accelerates its dissociation. Taken together, our findings suggest that SPL7013 compromises the stability of the R5 gp120-CD4 complex, potentially preventing the accrual of the requisite number of gp120-CD4 complexes across the virus-cell interface, thereby blocking virus entry.

The potential of HIV-1 nanotherapeutics: from in vitro studies to clinical trials

Since its discovery almost three decades ago, HIV-1 has grown into the most aggressive pandemic of modern time. Following the implementation of combination antiretroviral therapy, the pathological outcome of HIV infection has substantially improved. However, combination antiretroviral therapy is limited by several factors including, long-term toxicity, serious side effects and complex dosing regimens, and so on. In this regard, researchers have directed their attention toward enhancing current treatment strategies and/or developing alternative HIV-1 therapeutics. In recent years, this attention has fixated on nanomedicine-based anti-HIV therapeutics (HIV-1 nanotherapeutics). In the present study, we have reviewed several HIV-1 nanotherapeutics that have shown success at the preclinical level and/or Phase I/II clinical trials. We also discuss the possible benefits of these nanomedicine-based approaches and their future outlook.

Development of water-soluble polyanionic carbosilane dendrimers as novel and highly potent topical anti-HIV-2 microbicides

The development of topical microbicide formulations for vaginal delivery to prevent HIV-2 sexual transmission is urgently needed. Second- and third-generation polyanionic carbosilane dendrimers with a silicon atom core and 16 sulfonate (G2-S16), napthylsulfonate (G2-NS16) and sulphate (G3-Sh16) end-groups have shown potent and broad-spectrum anti-HIV-1 activity. However, their antiviral activity against HIV-2 and mode of action have not been probed. Cytotoxicity, anti-HIV-2, anti-sperm and antimicrobial activities of dendrimers were determined. Analysis of combined effects of triple combinations with tenofovir and raltegravir was performed by using CalcuSyn software. We also assessed the mode of antiviral action on the inhibition of HIV-2 infection through a panel of different in vitro antiviral assays: attachment, internalization in PBMCs, inactivation and cell-based fusion. Vaginal irritation and histological analysis in female BALB/c mice were evaluated. Our results suggest that G2-S16, G2-NS16 and G3-Sh16 exert anti-HIV-2 activity at an early stage of viral replication inactivating the virus, inhibiting cell-to-cell HIV-2 transmission, and blocking the binding of gp120 to CD4, and the HIV-2 entry. Triple combinations with tenofovir and raltegravir increased the anti-HIV-2 activity, consistent with synergistic interactions (CIwt: 0.33-0.66). No vaginal irritation was detected in BALB/c mice after two consecutive applications for 2 days with 3% G2-S16. Our results have clearly shown that G2-S16, G2-NS16 and G3-Sh16 have high potency against HIV-2 infection. The modes of action confirm their multifactorial and non-specific ability, suggesting that these dendrimers deserve further studies as potential candidate microbicides to prevent vaginal/rectal HIV-1/HIV-2 transmission in humans.