Anti-HIV efficacy and biodistribution of nucleoside reverse transcriptase inhibitors delivered as squalenoylated prodrug nanoassemblies

Nanoparticle-based strategies to target HIV-infected cells

Antiretroviral drugs employed for the treatment of human immunodeficiency virus (HIV) infections have remained largely ineffective due to their poor bioavailability, numerous adverse effects, modest uptake in infected cells, undesirable drug-drug interactions, the necessity for long-term drug therapy, and lack of access to tissues and reservoirs. Nanotechnology-based interventions could serve to overcome several of these disadvantages and thereby improve the therapeutic efficacy of antiretrovirals while reducing the morbidity and mortality due to the disease. However, attempts to use nanocarriers for the delivery of anti-retroviral drugs have started gaining momentum only in the past decade. This review explores in-depth the various nanocarriers that have been employed for the treatment of HIV infections highlighting their merits and possible demerits.

Prodrug Therapies for Infectious and Neurodegenerative Diseases

Prodrugs are bioreversible drug derivatives which are metabolized into a pharmacologically active drug following chemical or enzymatic modification. This approach is designed to overcome several obstacles that are faced by the parent drug in physiological conditions that include rapid drug metabolism, poor solubility, permeability, and suboptimal pharmacokinetic and pharmacodynamic profiles. These suboptimal physicochemical features can lead to rapid drug elimination, systemic toxicities, and limited drug-targeting to disease-affected tissue. Improving upon these properties can be accomplished by a prodrug design that includes the careful choosing of the promoiety, the linker, the prodrug synthesis, and targeting decorations. We now provide an overview of recent developments and applications of prodrugs for treating neurodegenerative, inflammatory, and infectious diseases. Disease interplay reflects that microbial infections and consequent inflammation affects neurodegenerative diseases and vice versa, independent of aging. Given the high prevalence, personal, social, and economic burden of both infectious and neurodegenerative disorders, therapeutic improvements are immediately needed. Prodrugs are an important, and might be said a critical tool, in providing an avenue for effective drug therapy.

Meta-Analysis of Drug Delivery Approaches for Treating Intracellular Infections

This meta-analysis aims to evaluate the trend, methodological quality and completeness of studies on intracellular delivery of antimicrobial agents. PubMed, Embase, and reference lists of related reviews were searched to identify original articles that evaluated carrier-mediated intracellular delivery and pharmacodynamics (PD) of antimicrobial therapeutics against intracellular pathogens in vitro and/or in vivo. A total of 99 studies were included in the analysis. The most commonly targeted intracellular pathogens were bacteria (62.6%), followed by viruses (16.2%) and parasites (15.2%). Twenty-one out of 99 (21.2%) studies performed neither microscopic imaging nor flow cytometric analysis to verify that the carrier particles are present in the infected cells. Only 31.3% of studies provided comparative inhibitory concentrations against a free drug control. Approximately 8% of studies, albeit claimed for intracellular delivery of antimicrobial therapeutics, did not provide any experimental data such as microscopic imaging, flow cytometry, and in vitro PD. Future research on intracellular delivery of antimicrobial agents needs to improve the methodological quality and completeness of supporting data in order to facilitate clinical translation of intracellular delivery platforms for antimicrobial therapeutics.

Gemcitabine Lipid Prodrugs: The Key Role of the Lipid Moiety on the Self-Assembly into Nanoparticles

A small library of amphiphilic prodrugs has been synthesized by conjugation of gemcitabine (Gem) (a hydrophilic nucleoside analogue) to a series of lipid moieties and investigated for their capacity to spontaneously self-assemble into nanosized objects by simple nanoprecipitation. Four of these conjugates formed stable nanoparticles (NPs), while with the others, immediate aggregation occurred, whatever the tested experimental conditions. Whether such capacity could have been predicted based on the prodrug physicochemical features was a matter of question. Among various parameters, the hydrophilic-lipophilic balance (HLB) value seemed to hold a predictive character. Indeed, we identified a threshold value which well correlated with the tendency (or not) of the synthesized prodrugs to form stable nanoparticles. Such a hypothesis was further confirmed by broadening the analysis to Gem and other nucleoside prodrugs already described in the literature. We also observed that, in the case of Gem prodrugs, the lipid moiety affected not only the colloidal properties but also the in vitro anticancer efficacy of the resulting nanoparticles. Overall, this study provides a useful demonstration of the predictive potential of the HLB value for lipid prodrug NP formulation and highlights the need of their opportune in vitro screening, as optimal drug loading does not always translate in an efficient biological activity.

Synthesis and Biopharmaceutical Characterization of Amphiphilic Squalenyl Derivative Based Versatile Drug Delivery Platform

Limited drug loading capacity (LC), mostly below 5% w/w, is a significant drawback of nanoparticulate drug delivery systems (DDS). Squalenoylation technology, which employs bioconjugation of squalenyl moiety and drug, allows self-assemble of nanoparticles (NPs) in aqueous media with significantly high LC (>30% w/w). The synthesis and particle preparation of squalenoylated prodrugs are, however, not facile for molecules with multiple reactive groups. Taking a different approach, we describe the synthesis of amphiphilic squalenyl derivatives (SqDs) as well as the physicochemical and biopharmaceutical characterizations of their self-assembled NPs as DDSs. The SqDs included in this study are (i) cationic squalenyl diethanolamine (ii) PEGylated SqD (PEG 750 Da), (iii) PEGylated SqD (PEG 3,000 Da), and (iv) anionic squalenyl hydrogen sulfate. All four SqDs self-assemble into NPs in a size range from 100 to 200 nm in an aqueous solution. Furthermore, all NP derivatives demonstrate appropriate biocompatibility and adequate colloidal stability in physiological relevant pH environments. The mucoprotein binding of PEGylated NPs is reduced compared to the charged NPs. Most importantly, this technology allows excellent LC (at maximum of 45% w/w) of a wide range of multifunctional compounds, varying in physicochemical properties and molecular weight. Interestingly, the drug release profile can be tuned by different loading methods. In summary, the SqD-based NPs appear as versatile drug delivery platforms.

Stacking as a Key Property for Creating Nanoparticles with Tunable Shape: The Case of Squalenoyl-Doxorubicin

The development of elongated nanoparticles for drug delivery is of growing interest in recent years, due to longer blood circulation and improved efficacy compared to spherical counterparts. Squalenoyl-doxorubicin (SQ-Dox) conjugate was previously shown to form elongated nanoparticles with improved therapeutic efficacy and decreased toxicity compared to free doxorubicin. By using experimental and computational techniques, we demonstrate here that the specific physical properties of SQ-Dox, which include stacking and electrostatic interactions of doxorubicin as well as hydrophobic interactions of squalene, are involved in the formation of nanoassemblies with diverse elongated structures. We show that SQ-Dox bioconjugate concentration, ionic strength, and anion nature can be used to modulate the shape and stiffness of SQ-Dox nanoparticles. As those parameters are involved in nanoparticle behavior in biological media, these findings could bring interesting opportunities for drug delivery and serve as an example for the design of original nanodrugs with stacking properties tuned for particular clinical purposes.

Fabrication of redox-responsive doxorubicin and paclitaxel prodrug nanoparticles with microfluidics for selective cancer therapy

Cancer is an exceptionally confounding disease that demands the development of powerful drug/drugs, without inducing heavy adverse side effects. Thus, different approaches have been applied to improve the targeted delivery of cancer drugs: for example by using nanocarriers. However, nanocarriers are foreign materials, which need further validation for their biocompatibility and biodegradability. In this study, we have chemically conjugated the hydrophilic anticancer drug doxorubicin (DOX) with the hydrophobic drug paclitaxel (PTX) through a redox-sensitive disulfide bond, abbreviated to DOX-S-S-PTX. Subsequently, due to its amphiphilic characterization, the prodrug can self-assemble into nanoparticles under microfluidic nanoprecipitation. These novel prodrug nanoparticles have a super-high drug loading degree of 89%, which is impossible to achieve by any nanocarrier systems, and can be tailored to 180 nm to deliver themselves to the target, and release DOX and PTX under redox conditions, which are often found in cancer cells. By evaluating cell viability in MDA-MB-231, MDA-MB-231/ADR and MEF cell lines, we observed that the prodrug nanoparticles effectively killed the cancer cells, and selectively conquered the MDA-MB-231/ADR. Meanwhile, MEF cells were spared due to their lack of a redox condition. The cell interaction results show that the reduced intermediate of the prodrug can also bind to parent drug biological targets. The hemolysis results show that the nanoparticles are biocompatible in blood. Computer modelling suggested that the prodrug is unlikely to bind to biological targets that parent drugs still strongly interact with. Finally, we confirm that the prodrug nanoparticles have no therapeutic effect in blood or healthy cells, but can selectively eliminate the cancer cells that meet the redox conditions to cleave the disulfide bond and release the drugs DOX and PTX.

From poly(alkyl cyanoacrylate) to squalene as core material for the design of nanomedicines

This review article covers the most important steps of the pioneering work of Patrick Couvreur and tries to shed light on his outstanding career that has been a source of inspiration for many decades. His discovery of biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) has opened large perspectives in nanomedicine. Indeed, NPs made from various types of alkyl cyanoacrylate monomers have been used in different applications, such as the treatment of intracellular infections or the treatment of multidrug resistant hepatocarcinoma. This latest application led to the Phase III clinical trial of Livatag^®, a PACA nanoparticulate formulation of doxorubicin. Despite the success of PACA NPs, the development of a novel type of NP with higher drug loadings and lower burst release was tackled by the discovery of squalene-based nanomedicines where the drug is covalently linked to the lipid derivative and the resulting conjugate is self-assembled into NPs. This pioneering work was accompanied by a wide range of novel applications which mainly dealt with the management of unmet medical needs (e.g. pancreatic cancer, brain ischaemia and spinal cord injury).

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.

Nanodelivery systems and stabilized solid-drug nanoparticles for orally administered medicine: current landscape

The use of nanoparticles as a means of targeted delivery of therapeutics and imaging agents could greatly enhance the transport of biologically active contents to specific target tissues, while avoiding or reducing potentially undesired side effects. Generally speaking, the oral route of administration is associated with good patient compliance, as it is convenient, economical, noninvasive, and does not require special training. Here, we review the progress of the utilization of nanodelivery-system carriers or stabilized solid-drug nanoparticles following oral administration, with particular attention on toxicological data. Mechanisms of cytotoxicity are discussed and the problem of extrapolating knowledge to human scenarios highlighted. Additionally, issues associated with administration of drugs via the oral route are underlined, while strategies utilized to overcome these are highlighted. This review aims to offer a balanced overview of strategies currently being used in the application of nanosize constructs for oral medical applications.

Applications and perspectives of nanomaterials in novel vaccine development

Vaccines show great potential for both prophylactic and therapeutic use in infections, cancer, and other diseases. With the rapid development of bio-technologies and materials sciences, nanomaterials are playing essential roles in novel vaccine formulations and can boost antigen effectiveness by operating as delivery systems to enhance antigen processing and/or as immune-potentiating adjuvants to induce or potentiate immune responses. The effect of nanoparticles in vaccinology showed enhanced antigen stability and immunogenicity as well as targeted delivery and slow release. However, obstacles remain due to the lack of fundamental knowledge on the detailed molecular working mechanism and in vivo bio-effects of nanoparticles. This review provides a broad overview of the current improvements in nanoparticles in vaccinology. Modern nanoparticle vaccines are classified by the nanoparticles' action based on either delivery system or immune potentiator approaches. The mechanisms of interaction of nanoparticles with the antigens and the immune system are discussed. Nanoparticle vaccines approved for use are also listed. A fundamental understanding of the in vivo bio-distribution and the fate of nanoparticles will accelerate the rational design of new nanoparticles comprising vaccines in the future.

Synthesis of a deuterated probe for the confocal Raman microscopy imaging of squalenoyl nanomedicines

The synthesis of ω-di-(trideuteromethyl)-trisnorsqualenic acid has been achieved from natural squalene. The synthesis features the use of a Shapiro reaction of acetone-d 6 trisylhydrazone as a key step to implement the terminal isopropylidene-d 6 moiety. The obtained squalenic acid-d 6 has been coupled to gemcitabine to provide the deuterated analogue of squalenoyl gemcitabine, a powerful anticancer agent endowed with self-assembling properties. The Raman spectra of both deuterated and non-deuterated squalenoyl gemcitabine nanoparticles displayed significant Raman scattering signals. They revealed no differences except from the deuterium peak patterns in the silent spectral region of cells. This paves the way for label-free intracellular trafficking studies of squalenoyl nanomedicines.

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.

Improving bioavailability and biodistribution of anti-HIV chemotherapy

In the context of the treatment of HIV/AIDS, many improvements have been achieved since the introduction of the combination therapy (HAART). Nevertheless, no cure for this disease has been so far possible, because of some particular features of the therapies. Among them, two important ones have been selected and will be the subject of this review. The first main concern in the treatments is the poor drug bioavailability, resulting in repeated administrations and therefore a demanding compliance (drug regimens consist of multiple drugs daily intake, and non-adherence to therapy is among the important reasons for treatment failure). A second important challenge is the need to target the drugs into the so-called reservoirs and sanctuaries, i.e. cells or body compartments where drugs cannot penetrate or are distributed in sub-active concentrations. The lack of antiviral action in these regions allows the virus to lie latent and start to replicate at any moment after therapy suspension. Recent drug delivery strategies addressing these two limitations will be presented in this review. In the first part, strategies to improve the bioavailability are proposed in order to overcome the absorption or the target cell barrier, or to extend the efficacy time of drugs. In the second section, the biodistribution issues are considered in order to target the drugs into the reservoirs and the sanctuaries, in particular the mononuclear phagocyte system and the brain.

Effects of siRNA on RET/PTC3 junction oncogene in papillary thyroid carcinoma: from molecular and cellular studies to preclinical investigations

RET/PTC3 junction oncogene is typical of radiation-induced childhood papillary thyroid carcinoma (PTC) with a short latency period. Since, RET/PTC3 is only present in the tumour cells, thus represents an interesting target for specific therapy by small interfering RNA (siRNA). Our aim is to demonstrate in vitro and in vivo molecular and cellular effects of siRNA on RET/PTC3 knockdown for therapeutic application.First, we established a novel cell line stably expressing RET/PTC3 junction oncogene, named RP3 which was found tumorigenic in nude mice compared to NIH/3T3 mouse fibroblasts. Among four siRNAs and five concentrations tested against RET/PTC3, an efficient siRNA RET/PTC3 and an appropriate dose (50 nM) were selected which showed significant inhibition (p<0.001) of gene (RT-qPCR) and protein (Western blot) expressions. This siRNA was found efficient in RP3 cells (harbouring RET/PTC3) but non-efficient in BHP10-3 SCmice cell line (harbouring RET/PTC1) showing that a specific siRNA against fusion sequence is required to target the junction oncogene. In vitro siRNA RET/PTC3 showed significant (p<0.001) inhibitory effects on RP3 cell viability (MTT assay) and on invasion/migration (IncuCyte scratch test) with blockage of cell cycle at G0/G1 phase (flow cytometry) and induced apoptosis by caspase-3 and PARP1 cleavage (WB). After intravenous injection in nude mice, respective squalene (SQ) nanoparticles (NPs) of siRNA RET/PTC3 significantly (p<0.001) reduced RP3 tumour growth, oncogene and oncoprotein expressions, induced apoptosis and partially restored differentiation (decrease in Ki67). Hence, our findings highly support the use of siRNA RET/PTC3-SQ NPs as a new promising treatment for patients affected by PTC expressing RET/PTC3.

Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury

There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, such as adenosine, are inefficient upon systemic administration because of their fast metabolization and rapid clearance from the bloodstream. Here, we show that conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allows prolonged circulation of this nucleoside, providing neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This Article shows, for the first time, that a hydrophilic and rapidly metabolized molecule such as adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.