Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) Prepared by Microwave and Ultrasound-Assisted Synthesis: Promising Green Strategies for the Nanoworld.

Many pharmaceutically active molecules are highly lipophilic, which renders their administration and adsorption in patients extremely challenging. Among the countless strategies to overcome this problem, synthetic nanocarriers have demonstrated superb efficiency as drug delivery systems, since encapsulation can effectively prevent a molecules' degradation, thus ensuring increased biodistribution. However, metallic and polymeric nanoparticles have been frequently associated with possible cytotoxic side effects. Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), which are prepared with physiologically inert lipids, therefore emerged as an ideal strategy to bypass toxicities issues and avoid the use of organic solvents in their formulations. Different approaches to preparation, using only moderate amounts of external energy to facilitate a homogeneous formation, have been proposed. Greener synthesis strategies have the potential to provide faster reactions, more efficient nucleation, better particle size distribution, lower polydispersities, and furnish products with higher solubility. Particularly microwave-assisted synthesis (MAS) and ultrasound-assisted synthesis (UAS) have been utilized in the manufacturing of nanocarrier systems. This narrative review addresses the chemical aspects of those synthesis strategies and their positive influence on the characteristics of SLNs and NLCs. Furthermore, we discuss the limitations and future challenges for the manufacturing processes of both types of nanoparticles.

Dextran Nanocapsules with ω-3 in Their Nucleus: An Innovative Nanosystem for Imiquimod Transdermal Delivery.

Transdermal administration of molecules across the skin has gained interest because it can be considered a non-invasive route compared with traditional ones. However, going through the skin is challenging due to the presence of the stratum corneum, the main barrier of substances. For this reason, the goal of this research was the combination of omega-3 (ω-3) and a dextran sulfate assembly in a nanostructure form, which allows passage through the skin and improves the bioavailability and the therapeutic profiles of active molecules, such as imiquimod. Here we report a new colloidal system, named dextran nanocapsules, with ω-3 in its nucleus and a coat made of dextran sulfate with a size ~150 nm, monomodal distribution, and negative zeta potential (~-33 mV). This nanosystem encapsulates imiquimod with high efficacy (~86%) and can release it in a controlled fashion following Korsmeyer-Peppas kinetics. This formulation is stable under storage and physiological conditions. Furthermore, a freeze-dried product could be produced with different cryoprotectants and presents a good security profile in the HaCaT cell line. Ex vivo assays with newborn pig skin showed that dextran nanocapsules promote transdermal delivery and retention 10 times higher than non-encapsulated imiquimod. These promising results make this nanosystem an efficient vehicle for imiquimod transdermal delivery.

Effect of zeta potential of innovative lipid nanocapsules on triamcinolone transdermal delivery.

Two pegylated lipid nanocapsules for triamcinolone transdermal delivery were designed. Both present a size close to 50 nm and a single monomodal distribution in particle size (PI < 0.2), with a zeta potential of - 20 ± 2 and + 18 ± 1, respectively. The triamcinolone encapsulation efficacy varied between 68 and 80%. They proved to be stable under storage conditions (4 °C) for at least 6 months and at a physiological temperature, using different media, for 48 h. Also, they were shown not to affect cell viability at the concentrations used. For ex vivo transdermal experiments, newborn pig skin was used. With respect to the triamcinolone transdermal penetration, the nanocapsules were demonstrated to have an absorption promoting effect, both when the drug nanocapsules were in solution or loaded into the hydrogel, quantifying between 2 and 15 times more absorbed drug than the control. In addition, regarding the triamcinolone retained in the skin, it is observed that lipid nanocapsules act as triamcinolone promoters when the nanosystems were in solution and when they were included in the hydrogel. This vehicle showed a greater triamcinolone reservoir effect in comparison to the nanocapsules, proving to be a good vehicle to formulate triamcinolone transdermal delivery.

A new era in oxygen therapeutics? From perfluorocarbon systems to haemoglobin-based oxygen carriers.

Blood transfusion is the key to life in case of traumatic emergencies, surgeries and in several pathological conditions. An important goal of whole blood or red blood cell transfusion is the fast delivery of oxygen to vital organs and restoration of circulation volume. Whole blood or red blood cell transfusion has several limitations. Free haemoglobin not only loses its tetrameric configuration and extracts via the kidney leading to nephrotoxicity but also scavenges nitric oxide (NO), leading to vasoconstriction and hypertension. PFC based formulations transport oxygen in vivo, the contribution in terms of clinical outcome is challenging. The oxygen-carrying capacity is not the only criterion for the successful development of haemoglobin-based oxygen carriers (HBOCs). This review is a bird's eye view on the present state of the PFCs and HBOCs in which we analyzed the current modifications made or which are underway in development, their promises, and hurdles in clinical implementation.

The Importance of Nanocarrier Design and Composition for an Efficient Nanoparticle-Mediated Transdermal Vaccination.

The World Health Organization estimates that the pandemic caused by the SARS-CoV-2 virus claimed more than 3 million lives in 2020 alone. This situation has highlighted the importance of vaccination programs and the urgency of working on new technologies that allow an efficient, safe, and effective immunization. From this perspective, nanomedicine has provided novel tools for the design of the new generation of vaccines. Among the challenges of the new vaccine generations is the search for alternative routes of antigen delivery due to costs, risks, need for trained personnel, and low acceptance in the population associated with the parenteral route. Along these lines, transdermal immunization has been raised as a promising alternative for antigen delivery and vaccination based on a large absorption surface and an abundance of immune system cells. These features contribute to a high barrier capacity and high immunological efficiency for transdermal immunization. However, the stratum corneum barrier constitutes a significant challenge for generating new pharmaceutical forms for transdermal antigen delivery. This review addresses the biological bases for transdermal immunomodulation and the technological advances in the field of nanomedicine, from the passage of antigens facilitated by devices to cross the stratum corneum, to the design of nanosystems, with an emphasis on the importance of design and composition towards the new generation of needle-free nanometric transdermal systems.

Design of Chitosan Nanocapsules with Compritol 888 ATO® for Imiquimod Transdermal Administration. Evaluation of Their Skin Absorption by Raman Microscopy.

PURPOSE: Design imiquimod-loaded chitosan nanocapsules for transdermal delivery and evaluate the depth of imiquimod transdermal absorption as well as the kinetics of this absorption using Raman Microscopy, an innovative strategy to evaluate transdermal absorption. This nanovehicle included Compritol 888ATO®, a novel excipient for formulating nanosystems whose administration through the skin has not been studied until now. METHODS: Nanocapsules were made by solvent displacement method and their physicochemical properties was measured by DLS and laser-Doppler. For transdermal experiments, newborn pig skin was used. The Raman spectra were obtained using a laser excitation source at 532 nm and a 20/50X oil immersion objective. RESULTS: The designed nanocapsules, presented nanometric size (180 nm), a polydispersity index <0.2 and a zeta potential +17. The controlled release effect of Compritol was observed, with the finding that half of the drug was released at 24 h in comparison with control (p < 0.05). It was verified through Raman microscopy that imiquimod transdermal penetration is dynamic, the nanocapsules take around 50 min to penetrate the stratum corneum and 24 h after transdermal administration, the drug was in the inner layers of the skin. CONCLUSIONS: This study demonstrated the utility of Raman Microscopy to evaluate the drugs transdermal penetration of in the different layers of the skin. Graphical Abstract New imiquimod nanocapsules: evaluation of their skin absorption by Raman Microscopy and effect of the compritol 888ATO® in the imiquimod release profile.

Hyaluronic Acid Nanocapsules as a Platform for Needle-Free Vaccination.

Vaccination faces many challenges nowadays, and among them the use of adjuvant molecules and needle-free administration are some of the most demanding. The combination of transcutaneous vaccination and nanomedicine through a rationally designed new-formulation could be the solution to this problem. This study focuses on this rational design. For this purpose, new hyaluronic acid nanocapsules (HA-NCs) have been developed. This new formulation has an oily nucleus with immunoadjuvant properties (due to α tocopherol) and a shell made of hyaluronic acid (HA) and decorated with ovalbumin (OVA) as the model antigen. The resulting nanocapsules are smaller than 100 nm, have a negative superficial charge and have a population that is homogeneously distributed. The systems show high colloidal stability in storage and physiological conditions and high OVA association without losing their integrity. The elevated interaction of the novel formulation with the immune system was demonstrated through complement activation and macrophage viability studies. Ex vivo studies using a pig skin model show the ability of these novel nanocapsules to penetrate and retain OVA in higher quantities in skin when compared to this antigen in the control solution. Due to these findings, HA-NCs are an interesting platform for needle-free vaccination.

Influence of protamine shell on nanoemulsions as a carrier for cyclosporine-A skin delivery.

Novel protamine-based nanosystems have been studied for cyclosporine-A (CsA) skin delivery. Core-shell structure systems have been developed to this end. These vehicles have particles sizes of 200-300 nm, a low polydispersity index and a zeta potential which varies between -16 mV and +35 mV. The resulting four nanosystems efficiently encapsulated CsA in their oily nucleus (60-80%) and released this drug in a controlled manner. These formulations have shown a high stability in aqueous suspension in storage conditions at 4 °C (for at least 21 months) and in acetate buffer at a physiological temperature of 37 °C (for at least 24 h). Ex vivo transdermal diffusion experiments using Franz diffusion cells and 2- to 3-day-old pig skin as a biological barrier were performed. All nanoformulations designed produced an increase in CsA transdermal delivery and two of these nanosystems presented a marked promoting effect; the more relevant parameters were smaller particle size (200 ± 7 nm) and negative superficial charge. Finally, the ability of these nanosystems to enhance retention of CsA in the skin was also studied. The protamine disposition in the shell influenced CsA skin retention. Therefore, the incorporation of CsA into the nanosystems studied here makes them suitable vehicles for CsA transdermal administration.

Protamine Nanocapsules for the Development of Thermostable Adjuvanted Nanovaccines.

One of the main challenges in the development of vaccine has been to improve their stability at room temperature and eliminate the limitations associated with the cold chain storage. In this paper, we describe the development and optimization of thermostable nanocarriers consisting of an oily core with immunostimulating activity, containing squalene or α tocopherol surrounded by a protamine shell. The results showed that these nanocapsules can efficiently associate the recombinant hepatitis B surface antigen (rHBsAg) without compromising its antigenicity. Furthermore, the freeze-dried protamine nanocapsules were able to preserve the integrity and bioactivity of the associated antigen upon storage for at least 12 months at room temperature. In vitro studies evidenced the high internalization of the nanocapsules by immunocompetent cells, followed by cytokine secretion and complement activation. In vivo studies showed the capacity of rHBsAg-loaded nanocapsules to elicit protective levels upon intramuscular or intranasal administration to mice. Overall, our data indicate that protamine nanocapsules are an innovative thermostable nanovaccine platform for improved antigen delivery.

Lower-Sized Chitosan Nanocapsules for Transcutaneous Antigen Delivery.

Transcutaneous vaccination has several advantages including having a noninvasive route and needle-free administration; nonetheless developing an effective transdermal formulation has not been an easy task because skin physiology, particularly the stratum corneum, does not allow antigen penetration. Size is a crucial parameter for successful active molecule administration through the skin. Here we report a new core-shell structure rationally developed for transcutaneous antigen delivery. The resulting multifunctional carrier has an oily core with immune adjuvant properties and a polymeric corona made of chitosan. This system has a size of around 100 nm and a positive zeta potential. The new formulation is stable in storage and physiological conditions. Ovalbumin (OVA) was used as the antigen model and the developed nanocapsules show high association efficiency (75%). Chitosan nanocapsules have high interaction with the immune system which was demonstrated by complement activation and also did not affect cell viability in the macrophage cell line. Finally, ex vivo studies using a pig skin model show that OVA associated to the chitosan nanocapsules developed in this study penetrated and were retained better than OVA in solution. Thus, the physicochemical properties and their adequate characteristics make this carrier an excellent platform for transcutaneous antigen delivery.

Polymeric Nanocapsules for Vaccine Delivery: Influence of the Polymeric Shell on the Interaction With the Immune System.

The use of biomaterials and nanosystems in antigen delivery has played a major role in the development of novel vaccine formulations in the last few decades. In an effort to gain a deeper understanding of the interactions between these systems and immunocompetent cells, we describe here a systematic in vitro and in vivo study on three types of polymeric nanocapsules (NCs). These carriers, which contained protamine (PR), polyarginine (PARG), or chitosan (CS) in the external shell, and their corresponding nanoemulsion were prepared, and their main physicochemical properties were characterized. The particles had a mean particle size in the range 250-450 nm and a positive zeta potential (~30-40 mV). The interaction of the nanosystems with different components of the immune system were investigated by measuring cellular uptake, reactive oxygen species production, activation of the complement cascade, cytokine secretion profile, and MAP kinases/nuclear factor κB activation. The results of these in vitro cell experiments showed that the NC formulations that included the arginine-rich polymers (PR and PARG) showed a superior ability to trigger different immune processes. Considering this finding, protamine and polyarginine nanocapsules (PR and PARG NCs) were selected to assess the association of the recombinant hepatitis B surface antigen (rHBsAg) as a model antigen to evaluate their ability to produce a protective immune response in mice. In this case, the results showed that PR NCs elicited higher IgG levels than PARG NCs and that this IgG response was a combination of anti-rHBsAg IgG1/IgG2a. This work highlights the potential of PR NCs for antigen delivery as an alternative to other positively charged nanocarriers.

Rational design of protamine nanocapsules as antigen delivery carriers.

Current challenges in global immunization indicate the demand for new delivery strategies, which could be applied to the development of new vaccines against emerging diseases, as well as to improve safety and efficacy of currently existing vaccine formulations. Here, we report a novel antigen nanocarrier consisting of an oily core and a protamine shell, further stabilized with pegylated surfactants. These nanocarriers, named protamine nanocapsules, were rationally designed to promote the intracellular delivery of antigens to immunocompetent cells and to trigger an efficient and long-lasting immune response. Protamine nanocapsules have nanometric size, positive zeta potential and high association capacity for H1N1 influenza hemagglutinin, a protein that was used here as a model antigen. The new formulation shows an attractive stability profile both, as an aqueous suspension or a freeze-dried powder formulation. In vitro studies showed that protamine nanocapsules were efficiently internalized by macrophages without eliciting significant toxicity. In vivo studies indicate that antigen-loaded nanocapsules trigger immune responses comparable to those achieved with alum, even when using significantly lower antigen doses, thus indicating their adjuvant properties. These promising in vivo data, alongside with their versatility for the loading of different antigens and oily immunomodulators and their excellent stability profile, make these nanocapsules a promising platform for the delivery of antigens. CHEMICAL COMPOUNDS: Protamine sulphate (PubChem SID: 7849283), Sodium Cholate (PubChem CID: 23668194), Miglyol (PubChem CID: 53471835), α tocopherol (PubChem CID: 14985), Tween® 20(PubChem CID: 443314), Tween® 80(PubChem CID: 5281955), TPGS (PubChem CID: 71406).

Protamine-based nanoparticles as new antigen delivery systems.

The use of biodegradable nanoparticles as antigen delivery vehicles is an attractive approach to overcome the problems associated with the use of Alum-based classical adjuvants. Herein we report, the design and development of protamine-based nanoparticles as novel antigen delivery systems, using recombinant hepatitis B surface antigen as a model viral antigen. The nanoparticles, composed of protamine and a polysaccharide (hyaluronic acid or alginate), were obtained using a mild ionic cross-linking technique. The size and surface charge of the nanoparticles could be modulated by adjusting the ratio of the components. Prototypes with optimal physicochemical characteristics and satisfactory colloidal stability were selected for the assessment of their antigen loading capacity, antigen stability during storage and in vitro and in vivo proof-of-concept studies. In vitro studies showed that antigen-loaded nanoparticles induced the secretion of cytokines by macrophages more efficiently than the antigen in solution, thus indicating a potential adjuvant effect of the nanoparticles. Finally, in vivo studies showed the capacity of these systems to trigger efficient immune responses against the hepatitis B antigen following intramuscular administration, suggesting the potential interest of protamine-polysaccharide nanoparticles as antigen delivery systems.

Polypeptides and polyaminoacids in drug delivery.

INTRODUCTION: Advances achieved over the last few years in drug delivery have provided novel and versatile possibilities for the treatment of various diseases. Among the biomaterials applied in this field, it is worth highlighting the increasing importance of polyaminoacids and polypeptides. The appealing properties of these polymers are very promising for the design of novel compositions in a variety of drug delivery applications. AREAS COVERED: This review provides an overview on the general characteristics of polyaminoacids and polypeptides and briefly discusses different synthetic pathways for their production. This is followed by a detailed description of different drug delivery applications of these polymers, emphasizing those examples that already reached advanced preclinical development or have entered clinical trials. EXPERT OPINION: Polyaminoacids and polypeptides are gaining much attention in drug delivery due to their exceptional properties. Their application as polymers for drug delivery purposes has been sped up by the significant achievements related to their synthesis. Certainly, cancer therapy has benefited the most from these advances, although other fields such as vaccine delivery and alternative administration routes are also being successfully explored. The design of new entities based on polyaminoacids and polypeptides and the improved insight gained in drug delivery guarantee exciting findings in the near future.

Nanovaccines : nanocarriers for antigen delivery.

Vaccination has become one of the most important health interventions of our times, revolutionizing health care, and improving the quality of life and life expectancy of millions all over the world. In spite of this, vaccine research remains a vast field for innovation and improvement. Indeed, the shift towards the use of sub-unit antigens, much safer but less immunogenic, and the recognized need to facilitate the access to vaccines in the global framework is currently stimulating the search for safe and efficient adjuvants and delivery technologies. Within this context, nanocarriers have gained particular attention over the last years and appear as one of the most promising strategies for antigen delivery. A number of biomaterials and technologies can be used to design nanovaccines that fulfill the requirements of new vaccination approaches, such as single-dose and transmucosal immunization, critical for achieving a widespread coverage while reducing the overall costs in relation to traditional forms of vaccination. Here we present an overview of the current state of nanocarriers for antigen delivery, developed with the perspective of contributing to the global vaccination goal.

Passive and iontophoretic transdermal penetration of chlorpromazine.

The in vitro iontophoretic transdermal delivery of chlorpromazine (CPZ) across pig skin was investigated. Anodal iontophoresis considerably increased CPZ skin penetration and accumulation compared with the passive controls. The effect of CPZ concentration in the donor solution was studied (1.4-8.2 mM). A higher penetration was observed with an increase of the concentration. In addition, the effect of NaCl concentration was also studied (154-200 mM). As expected, CPZ iontophoretic transport decreased with NaCl content. Finally, the influence of the current density (0.20-0.50 mA/cm(2)) was investigated. The iontophoretic transport of CPZ tends to increase with current density, although this effect was not statistically significant between 0.35 and 0.5 mA/cm(2). On the whole, this work shows that iontophoresis may be used to improve the transdermal delivery of CPZ for the treatment of chronic psychosis.