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

Lipid Nanoparticles: Formulation, Production Methods and Characterization Protocols

Lipid nanoparticles (LNs) have emerged as advanced lipid-based delivery systems, offering an effective approach for encapsulating and protecting lipid-soluble bioactive compounds, increasing their bioavailability. Solid Lipid Nanoparticles (SLNs) and Nanostructured Lipid Carriers (NLCs) are particularly promising for bioactive compound entrapment. However, to fully exploit their potential, it is crucial to carefully select the appropriate lipid matrices and emulsifiers. This review offers a comprehensive, up-to-date examination, considering studies published in the last 15 years, of the chemical, physical, and structural characteristics of lipids employed in LN production, focusing on the key components of the formulations: lipid matrices, emulsifiers, and bioactive compounds. In addition, it provides an in-depth analysis of production methods, drawing on insights from the latest scientific literature, and emphasizes the most important characterization techniques for LNs. Key parameters, including particle size (PS), zeta potential (ZP), crystallinity, thermal behavior, morphology, entrapment efficiency (EE), load capacity (LC), and physical stability, are discussed. Ultimately, this review aims to identify critical factors for the successful production of stable LNs that efficiently encapsulate and deliver bioactive compounds, highlighting their significant potential for applications in food systems.

Nanoparticle-based flavonoid therapeutics: Pioneering biomedical applications in antioxidants, cancer treatment, cardiovascular health, neuroprotection, and cosmeceuticals

Flavonoids, a type of natural polyphenolic molecule, have garnered significant research interest due to their ubiquitous nature and diverse biological activities, including antioxidant, anti-inflammatory, and anticancer effects, making them appealing to various scientific disciplines. In this regard, the use of a flavonoid nanoparticle delivery system is to overcome low bioavailability, bioactivity, poor aqueous solubility, systemic absorption, and intensive metabolism. Therefore, this review summarizes the classification of nanoparticles (liposomes, polymeric, and solid lipid nanoparticles) and the advantages of using nanoparticle-flavonoid formulations to boost flavonoid bioavailability. Moreover, this review illustrated the pioneering biomedical applications of nanoparticle-based flavonoid therapeutics, as well as safety and toxicity considerations of using a flavonoid nanoparticle delivery system.

Uncovering the Emerging Prospects of Lipid-based Nanoparticulate Vehicles in Lung Cancer Management: A Recent Perspective

Lung cancer, a leading cause of cancer-related deaths globally, is gaining research interest more than ever before. Owing to the burden of pathogenesis on the quality of life of patients and subsequently the healthcare system, research efforts focus on its management and amelioration. In an effort to improve bioavailability, enhance stability, minimize adverse effects and reduce the incidence of resistance, nanotechnological platforms have been harnessed for drug delivery and improving treatment outcomes. Lipid nanoparticles, in particular, offer an interesting clinical opportunity with respect to the delivery of a variety of agents. These include synthetic chemotherapeutic agents, immunotherapeutic molecules, as well as phytoconstituents with promising anticancer benefits. In addition to this, these systems are being studied for their usage in conjunction with other treatment strategies. However, their applications remain limited owing to a number of challenges, chiefly clinical translation. There is a need to address the scalability of such technologies, in order to improve accessibility. The authors aim to offer a comprehensive understanding of the evolution of lipid nanoparticles and their application in lung cancer, the interplay of disease pathways and their mechanism of action and the potential for delivery of a variety of agents. Additionally, a discussion with respect to results from preclinical studies has also been provided. The authors have also provided a well-rounded insight into the limitations and future perspectives. While the possibilities are endless, there is a need to undertake focused research to expedite clinical translation and offer avenues for wider applications in disease management.

Combating multidrug-resistant (MDR) Staphylococcus aureus infection using terpene and its derivative

Multidrug-resistant (MDR) Staphylococcus aureus represents a major global health issue resulting in a wide range of debilitating infections and fatalities. The slow progression of new antibiotics, limited choices for treatment, and scarcity of new drug approvals create immense obstacles in new drug line development. S. aureus poses a significant public health risk, due to the emergence of methicillin-resistant (MRSA) and vancomycin-resistant strains (VRSA), necessitating novel antibiotics for effective control management. Current studies are delving into the terpenes' potential as an antimicrobial agent, indicating positive prospects as promising substitutes or complementary to conventional antibiotics. Concurrent reactions of terpenes with conventional antibiotics create synergistic effects that significantly enhance antibiotic efficacy. Accumulated evidence has shown that while efflux pump (e.g., NorA, TetK, and MepA) is revealed as an essential defense of S. aureus against antibiotics, terpene and its derivative act as its potent inhibitor, suggesting the promising potential of terpenes in combating those infectious pathogens. Furthermore, pronounced cell membrane disruptive activity and antibiofilm properties by terpenes have been exerted, signifying their significance as promising prevention against microbial pathogenesis and antimicrobial resistance. This review provides an overview of the potential of terpenes and their derivatives in combating S. aureus infections, highlighting their potential mechanisms of action (MOA), synergistic effects with conventional antibiotics, and challenges in clinical translation. The unique properties of terpenes offer an opportunity for their use in developing an exceptional defense strategy against antibiotic-resistant S. aureus.

Stearic acid nanoparticles increase acyclovir absorption by oral epithelial cells

OBJECTIVE

Acyclovir (ACY) is used to treat oral viral herpes but has low solubility and bioavailability. Stearic acid (SA) is lipophilic and can be combined with drugs. Therefore, this study aimed to characterize the properties of SA nanoparticles in increasing the cellular uptake of ACY by oral epithelial cells. The hypothesis was that SA nanoparticles increase sustained ACY release, are stable, and increase drug uptake.

METHODS

The production parameters (duration and amplitude of sonication) were optimized to produce solid lipid nanoparticles (SLN) of SA-containing ACY. Particle stability was characterized under different storage conditions (4 °C and 37 °C for 1, 15, and 45 days). SLN were further characterized for their pharmacokinetic profile, cytotoxicity, in vitro permeability, and ability to modulate gene expression and promote ACY uptake by oral epithelial cells.

RESULTS

Pharmacokinetic studies revealed sustained and diffusional release of ACY from the SLN, with an initial burst release of 15 min. After 45 d of storage, SLN kept at both 4 °C and 37 °C showed a maximum release of > 90 % of the drug at 120 min. Cells treated with SLN presented a significantly higher intracellular drug content than those treated with ACY and significantly increased the genetic expression of TJP-1, OCLN, and ECAD.

SIGNIFICANCE

The hypothesis was accepted as SA nanoparticles containing ACY can sustain drug delivery and enhance its absorption into epithelial cells. Therefore, SA nanoparticles are promising for improving ACY uptake in treating oral herpes and other infections caused by HSV-1.

Advances in nanoparticle-based therapeutics for ischemic stroke: Enhancing drug delivery and efficacy

Ischemic stroke, characterized by vascular occlusion, has recently emerged as one of the primary causes of mortality and disability worldwide. Conventional treatment modalities, such as thrombolytic and neuroprotective therapies, face numerous challenges, including limited bioavailability, significant neurotoxicity, suboptimal targeting, short half-life, and poor blood-brain barrier (BBB) penetration. Nanoparticle-based drug delivery systems present distinct advantages, such as small size, enhanced lipophilicity, and modifiability, which can potentially address these limitations. Utilizing nanoparticles for drug delivery in ischemic stroke therapy offers improved drug bioavailability, reduced neurotoxicity, enhanced targeted delivery, prolonged drug half-life, and better dissolution kinetics. This review aims to provide a comprehensive overview of current strategies in preclinical studies for managing or preventing ischemic stroke from a nanomaterial perspective, highlighting the advantages and limitations of each approach.

Lipid-Based Nanoformulations for Drug Delivery: An Ongoing Perspective

Oils and lipids help make water-insoluble drugs soluble by dispersing them in an aqueous medium with the help of a surfactant and enabling their absorption across the gut barrier. The emergence of microemulsions (thermodynamically stable), nanoemulsions (kinetically stable), and self-emulsifying drug delivery systems added unique characteristics that make them suitable for prolonged storage and controlled release. In the 1990s, solid-phase lipids were introduced to reduce drug leakage from nanoparticles and prolong drug release. Manipulating the structure of emulsions and solid lipid nanoparticles has enabled multifunctional nanoparticles and the loading of therapeutic macromolecules such as proteins, nucleic acid, vaccines, etc. Phospholipids and surfactants with a well-defined polar head and carbon chain have been used to prepare bilayer vesicles known as liposomes and niosomes, respectively. The increasing knowledge of targeting ligands and external factors to gain control over pharmacokinetics and the ever-increasing number of synthetic lipids are expected to make lipid nanoparticles and vesicular systems a preferred choice for the encapsulation and targeted delivery of therapeutic agents. This review discusses different lipids and oil-based nanoparticulate systems for the delivery of water-insoluble drugs. The salient features of each system are highlighted, and special emphasis is given to studies that compare them.

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) for the delivery of bioactives sourced from plants: part II - applications and preclinical advancements

INTRODUCTION

Numerous purified bioactive compounds, crude extracts, and essential oils have demonstrated potent antioxidant, antimicrobial, anti-inflammatory, and antiviral properties, particularly in vitro or in silico; however, their in vivo applications are hindered by inadequate absorption and distribution in the organism. The incorporation of these phytochemicals into solid lipid nanoparticles (SLN) or nanostructured lipid carriers (NLC) has demonstrated significant advancements and represents a viable approach to improve their bioavailability through different administration routes.

AREAS COVERED

This review discusses the potential applications of SLN and NLC, loading bioactive compounds sourced from plants for the treatment of several diseases. An overview of the preclinical developments on the use of these lipid nanoparticles is also provided as well as the requisites to be launched on the market.

EXPERT OPINION

Medicinal plants have gained even more value for the pharmaceutical industries and their customers, leading to many studies exploring their therapeutic potential. Several bioactives derived from plants with antiviral, anticancer, neuroprotective, antioxidant, and antiaging properties have been proposed and loaded into lipid nanoparticles. In vitro and invivo studies corroborate the added value of SLN/NLC to improve the bioavailability of several bioactives. Surface modification to increase their stability and target delivery should be considering.

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) for the delivery of bioactives sourced from plants: part I - composition and production methods

INTRODUCTION

Nanoparticles (NPs) are widely used in the pharmaceutical field to treat various human disorders. Among these, lipid-based NPs (LNPs), including solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), are favored for drug/bioactive delivery due to their high stability, biocompatibility, encapsulation efficiency, and sustained/controlled release. These properties make them particularly suitable as carriers of compounds derived from plant sources.

AREAS COVERED

This study comprehensively explores updated literature knowledge on SLN and NLC, focusing on their composition and production methods for the specific delivery of drug/bioactive compounds derived from plant sources of interest in pharmaceutical and biomedical fields.

EXPERT OPINION

SLN and NLC facilitate the development of more effective natural product-based therapies, aiming to reduce dosage and minimize side effects. These delivery systems align with the consumer demands for safer and more sustainable products, as there are also based on biocompatible and biodegradable raw materials, thereby posing minimal toxicological risks while also meeting regulatory guidelines.

Lipid-based nanoparticles: innovations in ocular drug delivery

Ocular drug delivery presents significant challenges due to intricate anatomy and the various barriers (corneal, tear, conjunctival, blood-aqueous, blood-retinal, and degradative enzymes) within the eye. Lipid-based nanoparticles (LNPs) have emerged as promising carriers for ocular drug delivery due to their ability to enhance drug solubility, improve bioavailability, and provide sustained release. LNPs, particularly solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and cationic nanostructured lipid carriers (CNLCs), have emerged as promising solutions for enhancing ocular drug delivery. This review provides a comprehensive summary of lipid nanoparticle-based drug delivery systems, emphasizing their biocompatibility and efficiency in ocular applications. We evaluated research and review articles sourced from databases such as Google Scholar, TandFonline, SpringerLink, and ScienceDirect, focusing on studies published between 2013 and 2023. The review discusses the materials and methodologies employed in the preparation of SLNs, NLCs, and CNLCs, focusing on their application as proficient carriers for ocular drug delivery. CNLCs, in particular, demonstrate superior effectiveness attributed due to their electrostatic bioadhesion to ocular tissues, enhancing drug delivery. However, continued research efforts are essential to further optimize CNLC formulations and validate their clinical utility, ensuring advancements in ocular drug delivery technology for improved patient outcomes.

Myrtenol-Loaded Fatty Acid Nanocarriers Protect Rat Brains Against Ischemia-Reperfusion Injury: Antioxidant and Anti-Inflammatory Effects

This research investigated the preventive effects of myrtenol (MYR), fatty acid nanocarriers (FANC), and myrtenol-loaded FANC (MYR + FANC) on neurological disturbance, stroke volume, the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and tumor necrosis factor-alpha (TNF-α) in the brain with ischemia-reperfusion injuries induced by middle cerebral artery occlusion (MCAO) in rats. Seventy two Wistar male rats were divided into six main groups. The groups were sham, ischemia-reperfusion group (MACO), MACO-MYR (50 mg/kg), MACO-FANC (50 and 100 mg/kg), and MACO-MYR + FANC (50 mg/kg). Stroke volume, neurological deficit scores, and the brain levels of MDA, SOD, and TNF-α were examined with TTC staining, observation, and ELISA, respectively. Pretreatment with MYR, FANC (100 mg/kg), and MYR + FANC reduced the neurological deficit score and cerebral infarction volume. MYR, FANC (100 mg/kg), and MYR + FANC pretreatment increased and decreased brain SOD and MDA levels compared to MACO group, respectively. The TNF-α level decreased in the MYR + FANC group compared to MCAO and MCAO-MYR groups in the brain. The use of FANC (100 mg/kg), MYR, and MYR + FANC has protective effects against oxidative stress and ischemia-reperfusion injury. FANC probably improve the bioavailability of MYR, as MYR+ FANC had more therapeutic effects on the reduction of ischemia-reperfusion injuries, inflammation, and oxidative stress.

Data-driven development of an oral lipid-based nanoparticle formulation of a hydrophobic drug

Due to its cost-effectiveness, convenience, and high patient adherence, oral drug administration normally remains the preferred approach. Yet, the effective delivery of hydrophobic drugs via the oral route is often hindered by their limited water solubility and first-pass metabolism. To mitigate these challenges, advanced delivery systems such as solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) have been developed to encapsulate hydrophobic drugs and enhance their bioavailability. However, traditional design methodologies for these complex formulations often present intricate challenges because they are restricted to a relatively narrow design space. Here, we present a data-driven approach for the accelerated design of SLNs/NLCs encapsulating a model hydrophobic drug, cannabidiol, that combines experimental automation and machine learning. A small subset of formulations, comprising 10% of all formulations in the design space, was prepared in-house, leveraging miniaturized experimental automation to improve throughput and decrease the quantity of drug and materials required. Machine learning models were then trained on the data generated from these formulations and used to predict properties of all SLNs/NLCs within this design space (i.e., 1215 formulations). Notably, formulations predicted to be high-performers via this approach were confirmed to significantly enhance the solubility of the drug by up to 3000-fold and prevented degradation of drug. Moreover, the high-performance formulations significantly enhanced the oral bioavailability of the drug compared to both its free form and an over-the-counter version. Furthermore, this bioavailability matched that of a formulation equivalent in composition to the FDA-approved product, Epidiolex®.

Preparation and characterization of novel nanostructured lipid carriers (NLC) and solid lipid nanoparticles (SLN) containing coenzyme Q10 as potent antioxidants and antityrosinase agents

We developed novel and optimal Q10-NLC/SLN formulations as antioxidant and anti-tyrosinase agents. The formulations were analyzed for particle size, morphology, entrapment efficiency (EE %), and long-term stability. The in vitro drug release and in vivo skin penetration were evaluated using dialysis bag diffusion and Sprague Dawley (SD) rats, respectively. Cytotoxicity and protecting effects were assessed by AlamarBlue® assay, ROS level by DCFH-DA, and tyrosinase activity by l-DOPA assay, measuring the absorbance at 470 nm. The selected formulations had optimal surface characterizations, including Z-average size, PDI, and Zeta potential ranging from 125 to 207 nm, 0.09-0.22, and -7 to -24, respectively. They also exhibited physiochemical stability for up to 6 months and EE% above 80 %. The lipids ratio and co-Q10 amount as variable factors significantly affected particle size and zeta potential but were insignificant on PDI. The in vitro release diagram showed that Q10-NLC/SLN revealed a fast release during the first 8 h and prolonged release afterward. The in vivo skin permeation revealed a higher accumulative uptake of co-Q10 in the skin for Q10-NLC/SLN compared to Q10 emulsions. Both selected Q10-NLC and Q10-SLN could reduce intracellular ROS after exposure to H2O2. The Q10-NLC was found to be more potent for inhibiting the tyrosinase activity compared to O10-SLN. The results suggest that the new formulations are promising carriers for topical delivery of co-Q10 as an anti-aging and skin-whitening agent.

A Novel Approach for Dermal Application of Pranoprofen-Loaded Lipid Nanoparticles for the Treatment of Post-Tattoo Inflammatory Reactions

Recently, the number of people acquiring tattoos has increased, with tattoos gaining significant popularity in people between 20 and 40 years old. Inflammation is a common reaction associated with tattooing. The purpose of this study was to evaluate a nanostructured lipid carrier loading pranoprofen (PRA-NLC) as a tattoo aftercare formulation to reduce the inflammation associated with tattooing. In this context, the in vitro drug release and the ex vivo permeation-through-human-skin tests using Franz cells were appraised. The tolerance of our formulation on the skin was evaluated by studying the skin's biomechanical properties. In addition, an in vivo anti-inflammatory study was conducted on mice skin to evaluate the efficacy of the formulation applied topically after tattooing the animals. PRA-NLC showed a sustained release up to 72 h, and the amount of pranoprofen retained in the skin was found to be 33.48 µg/g/cm2. The formulation proved to be well tolerated; it increased stratum corneum hydration, and no signs of skin irritation were observed. Furthermore, it was demonstrated to be non-cytotoxic since the cell viability was greater than 80%. Based on these results, we concluded that PRA-NLC represents a suitable drug delivery carrier for the transdermal delivery of pranoprofen to alleviate the local skin inflammation associated with tattooing.

Engineering of VCAM-1-targeted nanostructured lipid carriers for delivery of melatonin against acute lung injury through SIRT1/NLRP3 mediated pyroptosis signaling pathway

Acute lung injury (ALI) is a prevalent and critical condition in clinical practice. Although certain pharmacological interventions have demonstrated benefits in preclinical studies, none have been proven entirely effective thus far. Therefore, the development of more efficient treatment strategies for ALI is imperative. In this study, we prepared nanostructured lipid carriers (NLCs) conjugated with anti-VCAM-1 antibodies to encapsulate melatonin (MLT), resulting in VCAM/MLT NLCs. This approach aimed to enhance the distribution of melatonin in lung vascular endothelial cells. The VCAM/MLT NLCs had an average diameter of 364 nm, high drug loading content, and a sustained drug release profile. Notably, the NLCs conjugated with anti-VCAM-1 antibodies demonstrated more specific cellular delivery mediated by the VCAM-1 receptors, increased cellular internalization, and enhanced accumulation in lung tissues. Treatment with VCAM/MLT NLCs effectively alleviated pulmonary inflammation by activating NLRP3 inflammasome-dependent pyroptosis through up-regulation of Sirtuin 1. Our findings suggest that VCAM/MLT NLCs demonstrate remarkable therapeutic effects on ALI in both in vitro and in vivo settings, making them a promising and efficient treatment strategy for ALI.

RNA Combined with Nanoformulation to Advance Therapeutic Technologies

Nucleic acid-based therapies have the potential to address numerous diseases that pose significant challenges to more traditional methods. RNA-based therapies have emerged as a promising avenue, utilizing nanoformulation treatments to target a range of pathologies. Nanoformulation offers several advantages compared to other treatment modalities, including targeted delivery, low toxicity, and bioactivity suitable for drug loading. At present, various types of nanoformulations are available, such as liposomes, polymeric nanoparticles (NPs), magnetic NPs, nanoshells, and solid lipid nanoparticles (SLNs). RNA-based therapy utilizes intracellular gene nanoparticles with messenger RNA (mRNA) emerging prominently in cancer therapy and immunotechnology against infectious diseases. The approval of mRNA-based technology opens doors for future technological advancements, particularly self-amplifying replicon RNA (repRNA). RepRNA is a novel platform in gene therapy, comprising viral RNA with a unique molecular property that enables the amplification of all encoded genetic information countless times. As a result, repRNA-based therapies have achieved significant levels of gene expression. In this context, the primary objective of this study is to furnish a comprehensive review of repRNA and its applications in nanoformulation treatments, with a specific focus on encapsulated nanoparticles. The overarching goal is to provide an extensive overview of the use of repRNA in conjunction with nanoformulations across a range of treatments and therapies.

Comparison of chitosan and SLN nano-delivery systems for antibacterial effect of tea tree (Melaleuca alternifolia) oil against P. aeruginosa and S. aureus

Treatment of wounds is challenging due to bacterial infections, including Staphylococcus aureus and Pseudomonas aeruginosa. Using the merits of alternative antimicrobials like tea tree oil (TTO) and nanotechnology, they can be helpful in combatting bacterial infections. Solid lipid nanoparticle (SLN) and chitosan (CS) nanoparticles show great potential as carriers for enhancing the stability and therapeutic benefits of oils. The aim of this study is to compare the influence of nanocarriers in enhancing the antibacterial effects of TTO. The study evaluates the physicochemical and antibacterial properties of TTO-SLN and TTO-CS against P. aeruginosa and S. aureus. The TTO-SLN nanoparticles showed a clear round shape with the average diameter size of 477 nm, while the TTO-CS nanoparticles illustrated very homogeneous morphology with 144 nm size. The encapsulation efficiency for TTO-CS and TTO-SLN was ∼88.3% and 73.5%, respectively. Minimum inhibitory concentration against S. aureus and P. aeruginosa for TTO-CS, TTO-SLN, and pure TTO were 35 and 45 µg ml-1, 130 and 170 µg ml-1, and 380 and 410 µg ml-1, respectively. Since TTO-CS revealed an impressively higher antimicrobial effects in comparison with TTO-SLN and TTO alone, it can be considered as a nanocarrier that produces the same antimicrobial effects with lower required amounts of the active substance.