Synthesis, structure-activity relationship and biological evaluation of tetracationic gemini Dabco-surfactants for transdermal liposomal formulations

Advances in the Synthesis of Biologically Active Quaternary Ammonium Compounds

This review provides a comprehensive overview of recent advancements in the design and synthesis of biologically active quaternary ammonium compounds (QACs). The covered scope extends beyond commonly reviewed antimicrobial derivatives to include synthetic agents with antifungal, anticancer, and antiviral properties. Additionally, this review highlights examples of quaternary ammonium compounds exhibiting activity against protozoa and herbicidal effects, as well as analgesic and anesthetic derivatives. The article also embraces the quaternary-ammonium-containing cholinesterase inhibitors and muscle relaxants. QACs, marked by their inherent permanent charge, also find widespread usage across diverse domains such as fabric softeners, hair conditioners, detergents, and disinfectants. The effectiveness of QACs hinges greatly on finding the right equilibrium between hydrophilicity and lipophilicity. The ideal length of the alkyl chain varies according to the unique structure of each QAC and its biological settings. It is expected that this review will provide comprehensive data for medicinal and industrial chemists to design and develop novel QAC-based products.

Terpenes-Modified Lipid Nanosystems for Temozolomide, Improving Cytotoxicity against Glioblastoma Human Cancer Cells In Vitro

Currently, increasing the efficiency of glioblastoma treatment is still an unsolved problem. In this study, a combination of promising approaches was proposed: (i) an application of nanotechnology approach to create a new terpene-modified lipid system (7% w/w), using soybean L-α-phosphatidylcholine, N-carbonyl-methoxypolyethylene glycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine for delivery of the chemotherapy drug, temozolomide (TMZ, 1 mg/mL); (ii) use of TMZ associated with natural compounds-terpenes (1% w/w) abietic acid and Abies sibirica Ledeb. resin (A. sibirica). Different concentrations and combinations of terpene-lipid systems were employed to treat human cancer cell lines T 98G (glioblastoma), M-Hela (carcinoma of the cervix) and human liver cell lines (Chang liver). The terpene-lipid systems appeared to be unilamellar and of spherical shape under transmission electron microscopy (TEM). The creation of a TMZ-loaded terpene-lipid nanosystem was about 100 nm in diameter with a negative surface charge found by dynamic light scattering. The 74% encapsulation efficiency allowed the release time of TMZ to be prolonged. The modification by terpenes of TMZ-loaded lipid nanoparticles improved by four times the cytotoxicity against human cancer T 98G cells and decreased the cytotoxicity against human normal liver cells. Terpene-modified delivery lipid systems are of potential interest as a combination therapy.

Mitochondria-Targeted Lipid Nanoparticles Loaded with Rotenone as a New Approach for the Treatment of Oncological Diseases

This research is based on the concept that mitochondria are a promising target for anticancer therapy, including thatassociated with the use of oxidative phosphorylation blockers (mitochondrial poisons). Liposomes based on L-α-phosphatidylcholine (PC) and cholesterol (Chol) modified with cationic surfactants with triphenylphosphonium (TPPB-n, where n = 10, 12, 14, and 16) and imidazolium (IA-n(OH), where n = 10, 12, 14, and 16) head groups were obtained. The physicochemical characteristics of liposomes at different surfactant/lipid molar ratios were determined by dynamic/electrophoretic light scattering, transmission electron microscopy, and spectrophotometry. The hydrodynamic diameter of all the systems was within 120 nm with a polydispersity index of no more than 0.24 even after 2 months of storage. It was shown that cationization of liposomes leads to an increase in the internalization of nanocontainers in pancreatic carcinoma (PANC-1) and duodenal adenocarcinoma (HuTu 80) cells compared with unmodified liposomes. Also, using confocal microscopy, it was shown that liposomes modified with TPPB-14 and IA-14(OH) statistically better colocalize with the mitochondria of tumor cells compared with unmodified ones. At the next stage, the mitochondrial poison rotenone (ROT) was loaded into cationic liposomes. It was shown that the optimal loading concentration of ROT is 0.1 mg/mL. The Korsmeyer-Peppas and Higuchi kinetic models were used to describe the release mechanism of ROT from liposomes in vitro. A significant reduction in the IC50 value for the modified liposomes compared with free ROT was shown and, importantly, a higher degree of selectivity for the HuTu 80 cell line compared with the normal cells (SI value is 307 and 113 for PC/Chol/TPPB-14/ROT and PC/Chol/IA-14(OH)/ROT, respectively) occurred. It was shown that the treatment of HuTu 80 cells with ROT-loaded cationic liposomal formulations leads to a dose-dependent decrease in the mitochondrial membrane potential.

Synthesis, Properties, and Biomedical Application of Dicationic Gemini Surfactants with Dodecane Spacer and Carbamate Fragments

A synthesis procedure and aggregation properties of a new homologous series of dicationic gemini surfactants with a dodecane spacer and two carbamate fragments (N,N'-dialkyl-N,N'-bis(2-(ethylcarbamoyloxy)ethyl)-N,N'-dimethyldodecan-1,6-diammonium dibromide, n-12-n(Et), where n = 10, 12, 14) were comprehensively described. The critical micelle concentrations of gemini surfactants were obtained using tensiometry, conductometry, spectrophotometry, and fluorimetry. The thermodynamic parameters of adsorption and micellization, i.e., maximum surface excess (Гmax), the surface area per surfactant molecule (Amin), degree of counterion binding (β), and Gibbs free energy of micellization (∆Gmic), were calculated. Functional activity of the surfactants, including the solubilizing capacity toward Orange OT and indomethacin, incorporation into the lipid bilayer, minimum inhibitory concentration, and minimum bactericidal and fungicidal concentrations, was determined. Synthesized gemini surfactants were further used for the modification of liposomes dual-loaded with α-tocopherol and donepezil hydrochloride for intranasal treatment of Alzheimer's disease. The obtained liposomes have high stability (more than 5 months), a significant positive charge (approximately + 40 mV), and a high degree of encapsulation efficiency toward rhodamine B, α-tocopherol, and donepezil hydrochloride. Korsmeyer-Peppas, Higuchi, and first-order kinetic models were used to process the in vitro release curves of donepezil hydrochloride. Intranasal administration of liposomes loaded with α-tocopherol and donepezil hydrochloride for 21 days prevented memory impairment and decreased the number of Aβ plaques by 37.6%, 40.5%, and 72.6% in the entorhinal cortex, DG, and CA1 areas of the hippocampus of the brain of transgenic mice with Alzheimer's disease model (APP/PS1) compared with untreated animals.

Conventional and PEGylated Liposomes as Vehicles of Copaifera sabulicola

Traditional medicine uses resin oils extracted from plants of the genus Copaifera for several purposes. Resin oils are being studied to understand and profile their pharmacological properties. The aim of this work was to prepare and to characterize conventional and pegylated liposomes incorporating resin oils or the hexanic extract obtained from Copaifera sabulicola (copaiba) leaves. The cytotoxic effect of these products was also investigated. Conventional and stealth liposomes with copaiba extract showed similar average diameters (around 126 nm), encapsulation efficiencies greater than 75% and were stable for 90 days. A cytotoxicity test was performed on murine glioma cells and the developed liposomes presented antiproliferative action against these cancer cells at the average concentration of 30 μg/mL. Phytochemicals encapsulated in PEGylated liposomes induced greater reduction in the viability of tumor cells. In addition, bioassay-s measured the cytotoxicity of copaiba resin oil (Copaifera sabulicola) in liposomes (conventional and PEGylated), which was also checked against pheochromocytoma PC12 cells. Its safety was verified in normal rat astrocytes. The results indicate that liposomes encapsulating copaiba oil showed cytotoxic activity against the studied tumor strains in a dose-dependent fashion, demonstrating their potential applications as a chemotherapeutic bioactive formulation.

Surface Modification of Lipid-Based Nanocarriers: A Potential Approach to Enhance Targeted Drug Delivery

Nanocarriers have the utmost significance for advancements in drug delivery and nanomedicine technology. They are classified as polymer-based nanocarriers, lipid-based nanocarriers, viral nanoparticles, or inorganic nanoparticles, depending on their constituent parts. Lipid-based nanocarrier systems have gained tremendous attention over the years because of their noteworthy properties like high drug-loading capacity, lower toxicity, better bioavailability and biocompatibility, stability in the gastrointestinal tract, controlled release, simpler scale-up, and validation process. Nanocarriers still have some disadvantages like poor drug penetration, limited drug encapsulation, and poor targeting. These disadvantages can be overcome by their surface modification. Surface-modified nanocarriers result in controlled release, enhanced penetration efficiency, and targeted medication delivery. In this review, the authors summarize the numerous lipid-based nanocarriers and their functionalization through various surface modifiers such as polymers, ligands, surfactants, and fatty acids. Recent examples of newly developing surface-modified lipid-based nanocarrier systems from the available literature, along with their applications, have been compiled in this work.

Preparation and characterization of a gemini surfactant-based biomimetic complex for gene delivery

Gemini surfactants (GS) have been explored as non-viral gene delivery systems. Nevertheless, their cytotoxicity and the limitations in the in vivo studies have impeded their development. To attenuate toxicity and further explore their possibilities in gene delivery, a series of GS (18-7-18)-based gene delivery systems complexed with red blood cell membranes (RBCM) or/and DOPE-PEG₂₀₀₀ (DP) were prepared and evaluated. EGFP-encoding plasmids were delivered via GS-based complexes and the efficiency of gene transfection was evaluated by imaging of the major organs after intravenous administration in mice and qPCR quantification in hepatocytes. In order to assess the safety of GS-based complexes, the hemolysis test, serum biochemical indices, H&E staining and CCK-8 test were examined. The results revealed that EGFP was primarily expressed in livers, and all complexes showed minimal acute toxicity to major organs. Moreover, we found that the dual incorporation of RBCM and DP could significantly elevate the transfection efficiency and cell viability in hepatocytes. Overall, the results indicated that GS-based complexes possessed great potential as vectors for gene delivery both in vivo and in vitro and the dual incorporation of RBCM and DP could be a promising gene delivery approach with high transfection efficacy and low toxicity.

Cationic Surfactants Based on Arginine-Phenylalanine and Arginine-Tryptophan: Synthesis, Aggregation Behavior, Antimicrobial Activity, and Biodegradation

Cationic surfactants have great potential as drug vehicles and for use in gene therapy (cationic vesicles made from cationic surfactants can encapsulate RNA or DNA for cellular transfer). They can also be used as antimicrobial and antifungal agents to treat human infections. In an era of increasing antimicrobial resistance, the development of new biocompatible surfactants suitable for application as antimicrobial agents is of high interest. In this work, a library of amino acid-based surfactants was synthesized, characterized and tested for antimicrobial activity. The head group architecture (number and type of amino acids, density of cationic charge, ionic character) and the hydrophobic moiety (alkyl chain length and position of the hydrophobic group) were systematically modified, and the effect on the surfactant biological and aggregation behavior was studied. Thus, the pKa values, micellization process, antimicrobial efficiency and biodegradability were evaluated. The critical micelle concentration values of the surfactants depended on their hydrophobic character, but changes in the polar head as well as the position and length of the alkyl chain also significantly affected activity against some of the tested microorganisms. Moreover, biodegradability was closely related to the hydrophobic character of the surfactant and attachment of the alkyl chain to the polar head. The structure-activity relationships established here may open perspectives for the design of effective biodegradable antimicrobial materials that can overcome emerging resistance.

Myostatin and its Regulation: A Comprehensive Review of Myostatin Inhibiting Strategies

Myostatin (MSTN) is a well-reported negative regulator of muscle growth and a member of the transforming growth factor (TGF) family. MSTN has important functions in skeletal muscle (SM), and its crucial involvement in several disorders has made it an important therapeutic target. Several strategies based on the use of natural compounds to inhibitory peptides are being used to inhibit the activity of MSTN. This review delivers an overview of the current state of knowledge about SM and myogenesis with particular emphasis on the structural characteristics and regulatory functions of MSTN during myogenesis and its involvements in various muscle related disorders. In addition, we review the diverse approaches used to inhibit the activity of MSTN, especially in silico approaches to the screening of natural compounds and the design of novel short peptides derived from proteins that typically interact with MSTN.

Customized cationic nanoemulsions loading triamcinolone acetonide for corneal neovascularization secondary to inflammatory processes

Customized cationic oil-in-water nanoemulsions (NEs) have been produced to improve the bioavailability of poorly water-soluble drugs, such as triamcinolone acetonide (TA). TA is a synthetic glucocorticoid with anti-inflammatory and antiangiogenic therapeutic properties and it is widely used as an effective treatment in ocular disorders. In this work, TA-NEs were characterized using two different custom-made cationic surfactants, showing a high positive surface charge favouring corneal penetration and a particle size below 300 nm. Both TA-NE formulations demonstrated to be stable at 4 °C during the first months of storage. Furthermore, TA-NEs were able to produce antiangiogenic effects in chicken membranes. The TA-NEs safety profile was evaluated using in vitro and in vivo ocular tolerance tests. Out of the two formulations, the one showing no irritant effects was screened in vivo demonstrating capacity to ameliorate ocular inflammation in New Zealand rabbits significantly, specially to reduce the risk of ocular inflammation processes, with antiangiogenic activity, and can therefore be exploited as a suitable formulation to avoid inflammatory reactions upon ocular surgical procedures, such as cataracts.

Development and Characterization of Nanoemulsions for Ophthalmic Applications: Role of Cationic Surfactants

The eye is a very complex organ comprising several physiological and physical barriers that compromise drug absorption into deeper layers. Nanoemulsions are promising delivery systems to be used in ocular drug delivery due to their innumerous advantages, such as high retention time onto the site of application and the modified release profile of loaded drugs, thereby contributing to increasing the bioavailability of drugs for the treatment of eye diseases, in particular those affecting the posterior segment. In this review, we address the main factors that govern the development of a suitable nanoemulsion formulation for eye administration to increase the patient’s compliance to the treatment. Appropriate lipid composition and type of surfactants (with a special emphasis on cationic compounds) are discussed, together with manufacturing techniques and characterization methods that are instrumental for the development of appropriate ophthalmic nanoemulsions.

Rational Design 2-Hydroxypropylphosphonium Salts as Cancer Cell Mitochondria-Targeted Vectors: Synthesis, Structure, and Biological Properties

It has been shown for a wide range of epoxy compounds that their interaction with triphenylphosphonium triflate occurs with a high chemoselectivity and leads to the formation of (2-hydroxypropyl)triphenylphosphonium triflates 3 substituted in the 3-position with an alkoxy, alkylcarboxyl group, or halogen, which were isolated in a high yield. Using the methodology for the disclosure of epichlorohydrin with alcohols in the presence of boron trifluoride etherate, followed by the substitution of iodine for chlorine and treatment with triphenylphosphine, 2-hydroxypropyltriphenylphosphonium iodides 4 were also obtained. The molecular and supramolecular structure of the obtained phosphonium salts was established, and their high antitumor activity was revealed in relation to duodenal adenocarcinoma. The formation of liposomal systems based on phosphonium salt 3 and L-α-phosphatidylcholine (PC) was employed for improving the bioavailability and reducing the toxicity. They were produced by the thin film rehydration method and exhibited cytotoxic properties. This rational design of phosphonium salts 3 and 4 has promising potential of new vectors for targeted delivery into mitochondria of tumor cells.

DABCO-Customized Nanoemulsions: Characterization, Cell Viability and Genotoxicity in Retinal Pigmented Epithelium and Microglia Cells

Quaternary derivatives of 1,4-diazabicyclo[2.2.2]octane (DABCO) and of quinuclidine surfactants were used to develop oil-in-water nanoemulsions with the purpose of selecting the best long-term stable nanoemulsion for the ocular administration of triamcinolone acetonide (TA). The combination of the best physicochemical properties (i.e., mean droplet size, polydispersity index, zeta potential, osmolality, viscoelastic properties, surface tension) was considered, together with the cell viability assays in ARPE-19 and HMC3 cell lines. Surfactants with cationic properties have been used to tailor the nanoemulsions’ surface for site-specific delivery of drugs to the ocular structure for the delivery of TA. They are tailored for the eye because they have cationic properties that interact with the anionic surface of the eye.

Elastic and Ultradeformable Liposomes for Transdermal Delivery of Active Pharmaceutical Ingredients (APIs)

Administration of active pharmaceutical ingredients (APIs) through the skin, by means of topical drug delivery systems, is an advanced therapeutic approach. As the skin is the largest organ of the human body, primarily acting as a natural protective barrier against permeation of xenobiotics, specific strategies to overcome this barrier are needed. Liposomes are nanometric-sized delivery systems composed of phospholipids, which are key components of cell membranes, making liposomes well tolerated and devoid of toxicity. As their lipid compositions are similar to those of the skin, liposomes are used as topical, dermal, and transdermal delivery systems. However, permeation of the first generation of liposomes through the skin posed some limitations; thus, a second generation of liposomes has emerged, overcoming permeability problems. Various mechanisms of permeation/penetration of elastic/ultra-deformable liposomes into the skin have been proposed; however, debate continues on their extent/mechanisms of permeation/penetration. In vivo bioavailability of an API administered in the form of ultra-deformable liposomes is similar to the bioavailability achieved when the same API is administered in the form of a solution by subcutaneous or epi-cutaneous injection, which demonstrates their applicability in transdermal drug delivery.

Biosurfactants: Properties and Applications in Drug Delivery, Biotechnology and Ecotoxicology

Surfactants are amphiphilic compounds having hydrophilic and hydrophobic moieties in their structure. They can be of synthetic or of microbial origin, obtained respectively from chemical synthesis or from microorganisms’ activity. A new generation of ecofriendly surfactant molecules or biobased surfactants is increasingly growing, attributed to their versatility of applications. Surfactants can be used as drug delivery systems for a range of molecules given their capacity to create micelles which can promote the encapsulation of bioactives of pharmaceutical interest; besides, these assemblies can also show antimicrobial properties. The advantages of biosurfactants include their high biodegradability profile, low risk of toxicity, production from renewable sources, functionality under extreme pH and temperature conditions, and long-term physicochemical stability. The application potential of these types of polymers is related to their properties enabling them to be processed by emulsification, separation, solubilization, surface (interfacial) tension, and adsorption for the production of a range of drug delivery systems. Biosurfactants have been employed as a drug delivery system to improve the bioavailability of a good number of drugs that exhibit low aqueous solubility. The great potential of these molecules is related to their auto assembly and emulsification capacity. Biosurfactants produced from bacteria are of particular interest due to their antibacterial, antifungal, and antiviral properties with therapeutic and biomedical potential. In this review, we discuss recent advances and perspectives of biosurfactants with antimicrobial properties and how they can be used as structures to develop semisolid hydrogels for drug delivery, in environmental bioremediation, in biotechnology for the reduction of production costs and also their ecotoxicological impact as pesticide alternative.

Recent Progress in Transdermal Nanocarriers and Their Surface Modifications

Transdermal drug delivery system (TDDS) is an attractive method for drug delivery with convenient application, less first-pass effect, and fewer systemic side effects. Among all generations of TDDS, transdermal nanocarriers show the greatest clinical potential because of their non-invasive properties and high drug delivery efficiency. However, it is still difficult to design optimal transdermal nanocarriers to overcome the skin barrier, control drug release, and achieve targeting. Hence, surface modification becomes a promising strategy to optimize and functionalize the transdermal nanocarriers with enhanced penetration efficiency, controlled drug release profile, and targeting drug delivery. Therefore, this review summarizes the developed transdermal nanocarriers with their transdermal mechanism, and focuses on the surface modification strategies via their different functions.

Long-Chain Ionic Liquids Based on Monoquaternary DABCO Cations and TFSI Anions: Towards Stable Electrolytes for Electrochemical Capacitors

The desirable properties of ionic liquids (ILs) enable their use in various branches of chemistry, through a wide range of applications, e. g. as organic electrolytes. In the present study, an efficient two-step method was developed for the synthesis of long-chain ionic liquids with alkyl derivatives of DABCO as cations and bis(trifluoromethane)sulfonimide as anions. ILs obtained with high yields (≥91 %) were solids with melting points that increased with the rise in the number of carbon atoms of the alkyl substituent in the bicyclic cation. The structure of the compounds was confirmed by spectroscopic methods and elemental analysis. All compounds were soluble in the main solvents except water and hexane. The solubility in organic solvents such as acetonitrile allowed the use of synthesized ILs in electrochemical capacitors. Electrochemical tests revealed that the ILs enhanced the conductivity of organic electrolytes. This phenomenon improved the cyclability and reduced the internal resistance of the electrochemical capacitors.

Self-Assembly of Amphiphilic Compounds as a Versatile Tool for Construction of Nanoscale Drug Carriers

This review focuses on synthetic and natural amphiphilic systems prepared from straight-chain and macrocyclic compounds capable of self-assembly with the formation of nanoscale aggregates of different morphology and their application as drug carriers. Since numerous biological species (lipid membrane, bacterial cell wall, mucous membrane, corneal epithelium, biopolymers, e.g., proteins, nucleic acids) bear negatively charged fragments, much attention is paid to cationic carriers providing high affinity for encapsulated drugs to targeted cells. First part of the review is devoted to self-assembling and functional properties of surfactant systems, with special attention focusing on cationic amphiphiles, including those bearing natural or cleavable fragments. Further, lipid formulations, especially liposomes, are discussed in terms of their fabrication and application for intracellular drug delivery. This section highlights several features of these carriers, including noncovalent modification of lipid formulations by cationic surfactants, pH-responsive properties, endosomal escape, etc. Third part of the review deals with nanocarriers based on macrocyclic compounds, with such important characteristics as mucoadhesive properties emphasized. In this section, different combinations of cyclodextrin platform conjugated with polymers is considered as drug delivery systems with synergetic effect that improves solubility, targeting and biocompatibility of formulations.

Self-Assembled Quaternary Ammonium-Containing Comb-Like Polyelectrolytes for the Hydrolysis of Organophosphorous Esters: Effect of Head Groups and Counter-Ions

The aim of this work was to increase the efficiency of catalytic systems for the hydrolytic cleavage of 4-nitrophenyl esters of phosphonic acids. Quaternary ammonium-containing comb-like polyelectrolytes («polymerized micelles») with ester cleavable fragments and a low aggregation threshold were used as catalysts. The synthesis of poly(11-acryloyloxyundecylammonium) surfactants with different counterions (Br^- , NO₃ ^- , CH₃ C₆ H₄ SO₃ ^- ) and head groups was realized by micellar free-radical polymerization. Molecular weight, critical association concentration, particle sizes and solubilization properties toward Orange OT were determined. Self-assemblies organized by poly(11-acryloyloxyundecyltrimethyl ammonium) bromide successfully catalyze the hydrolysis of 4-nitrophenyl butylchloromethylphosphonate up to two orders of magnitude compared to aqueous alkaline hydrolysis. The development of these catalysts is promising for industrial applications and organophosphorus compound detoxification.

Mazzola P, Souto EB, Chaud MV. Cachexia: Pathophysiology and Ghrelin Liposomes for Nose-to-Brain Delivery

Cachexia, a severe multifactorial condition that is underestimated and unrecognized in patients, is characterized by continuous muscle mass loss that leads to progressive functional impairment, while nutritional support cannot completely reverse this clinical condition. There is a strong need for more effective and targeted therapies for cachexia patients. There is a need for drugs that act on cachexia as a distinct and treatable condition to prevent or reverse excess catabolism and inflammation. Due to ghrelin properties, it has been studied in the cachexia and other treatments in a growing number of works. However, in the body, exogenous ghrelin is subject to very rapid degradation. In this context, the intranasal release of ghrelin-loaded liposomes to cross the blood-brain barrier and the release of the drug into the central nervous system may be a promising alternative to improve its bioavailability. The administration of nose-to-brain liposomes for the management of cachexia was addressed only in a limited number of published works. This review focuses on the discussion of the pathophysiology of cachexia, synthesis and physiological effects of ghrelin and the potential treatment of the diseased using ghrelin-loaded liposomes through the nose-to-brain route.

Nanopharmaceutics: Part II-Production Scales and Clinically Compliant Production Methods

Due the implementation of nanotechnologies in the pharmaceutical industry over the last few decades, new type of cutting-edge formulations-nanopharmaceutics-have been proposed. These comprise pharmaceutical products at the nanoscale, developed from different types of materials with the purpose to, e.g., overcome solubility problems of poorly water-soluble drugs, the pharmacokinetic and pharmacodynamic profiles of known drugs but also of new biomolecules, to modify the release profile of loaded compounds, or to decrease the risk of toxicity by providing site-specific delivery reducing the systemic distribution and thus adverse side effects. To succeed with the development of a nanopharmaceutical formulation, it is first necessary to analyze the type of drug which is to be encapsulated, select the type matrix to load it (e.g., polymers, lipids, polysaccharides, proteins, metals), followed by the production procedure. Together these elements have to be compatible with the administration route. To be launched onto the market, the selected production method has to be scaled-up, and quality assurance implemented for the product to reach clinical trials, during which in vivo performance is evaluated. Regulatory issues concerning nanopharmaceutics still require expertise for harmonizing legislation and a clear understanding of clinically compliant production methods. The first part of this study addressing "Nanopharmaceutics: Part I-Clinical trials legislation and Good Manufacturing Practices (GMP) of nanotherapeutics in the EU" has been published in Pharmaceutics. This second part complements the study with the discussion about the production scales and clinically compliant production methods of nanopharmaceutics.

Nanomaterials for Skin Delivery of Cosmeceuticals and Pharmaceuticals

Skin aging is described as dermatologic changes either naturally occurring over the course of years or as the result of the exposure to environmental factors (e.g., chemical products, pollution, infrared and ultraviolet radiations). The production of collagen and elastin, the main structural proteins responsible for skin strength and elasticity, is reduced during aging, while their role in skin rejuvenation can trigger a wrinkle reversing effect. Elasticity loss, wrinkles, dry skin, and thinning are some of the signs that can be associated with skin aging. To overcome skin aging, many strategies using natural and synthetic ingredients are being developed aiming to reduce the signs of aging and/or to treat age-related skin problems (e.g., spots, hyper- or hypopigmentation). Among the different approaches in tissue regeneration, the use of nanomaterials loaded with cosmeceuticals (e.g., phytochemicals, vitamins, hyaluronic acid, and growth factors) has become an interesting alternative. Based on their bioactivities and using different nanoformulations as efficient delivery systems, several cosmeceutical and pharmaceutical products are now available on the market aiming to mitigate the signs of aged skin. This manuscript discusses the state of the art of nanomaterials commonly used for topical administration of active ingredients formulated in nanopharmaceuticals and nanocosmeceuticals for skin anti-aging.