Modeling the effect of sonication parameters on size and dispersion temperature of solid lipid nanoparticles (SLNs) by response surface methodology (RSM)

Natural-Origin Betaine Surfactants as Promising Components for the Stabilization of Lipid Carriers

In the present work, we demonstrate studies involving the influence of the formulation composition on the physicochemical properties of nanocarriers: solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). Novel lipid-origin platforms were prepared using two "green" betaine-based surfactants, cocamidopropyl betaine (ROKAmina K30) and coco betaine (ROKAmina K30B), in combination with three different solid lipids, cetyl palmitate (CRODAMOL CP), trimyristin (Dynasan 114), and tristearin (Dynasan 118). Extensive optimization studies included the selection of the most appropriate lipid and surfactant concentration for effective SLN and NLC stabilization. The control parameters involving the hydrodynamic diameters of the obtained nanocarriers along with the size distribution (polydispersity index) were determined by dynamic light scattering (DLS), while shape and morphology were evaluated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Electrophoretic light scattering (ELS) and turbidimetric method (backscattering profiles) were used to assess colloidal stability. The studied results revealed that both betaine-stabilized SLN and NLC formulations containing CRODAMOL CP as lipid matrix are the most monodisperse and colloidally stable regardless of the other components and their concentrations used, indicating them as the most promising candidates for drug delivery nanosystems with a diverse range of potential uses.

Lyophilized Nasal Inserts of Atomoxetine HCl Solid Lipid Nanoparticles for Brain Targeting as a Treatment of Attention-Deficit/Hyperactivity Disorder (ADHD): A Pharmacokinetics Study on Rats

The study aims to investigate the ability of lyophilized nasal inserts of nanosized atomoxetine HCl solid lipid nanoparticles (ATM-SLNs) to transport atomoxetine (ATM) directly to the brain and overcome the first-pass metabolism. In this case, 16 formulae of (ATM-SLNs) were prepared using hot melt emulsification, stirring and ultrasonication method technique. A full factorial design was established with 2⁴ trials by optimization of four variables; lipid type (Compritol 888 ATO or stearic acid) (X1), lipid to drug ratio [(1:2) or (2:1)] (X2), span 60: Pluronic f127 ratio [(1:3) or (3:1)] (X3) and probe sonication time (five or ten minutes) (X4). The prepared SLNs were characterized for entrapment efficiency (EE%), in-vitro drug release after 30 min (Q30min), particle size (PS), zeta potential (ZP) and polydispersity index (PDI). Design Expert^® software was used to select the optimum two formulae. The morphological examination for the optimum two formulae was carried out using a transmission electron microscope (TEM). Furthermore, eight lyophilized nasal inserts were prepared by using a 2³ full factorial design by optimization of three variables: type of (ATM-SLNs) formula (X1), type of polymer (NOVEON AA1 or HPMC K100m) (X2) and concentration of polymer (X3). They were evaluated for nasal inserts' physicochemical properties. The two optimum inserts were selected by Design Expert^® software. The two optimum insets with the highest desirability values were (S4 and S8). They were subjected to DSC thermal stability study and in-vivo study on rats. They were compared with atomoxetine oral solution, atomoxetine (3 mg/kg, intraperitoneal injection) and the pure atomoxetine solution loaded in lyophilized insert. (ATM-SLNs) showed EE% range of (41.14 mg ± 1.8% to 90.6 mg ± 2.8%), (Q30min%) of (27.11 ± 5.9% to 91.08 ± 0.15%), ZP of (-8.52 ± 0.75 to -28.4 ± 0.212% mV), PS of (320.9 ± 110.81% nm to 936.7 ± 229.6% nm) and PDI of (0.222 ± 0.132% to 0.658 ± 0.03%). Additionally, the two optimum (ATM-SLNs) formulae chosen, i.e., F7 and F9 showed spherical morphology. Nasal inserts had assay of drug content of (82.5 ± 2.5% to 103.94 ± 3.94%), Q15min% of (89.9 ± 6.4% to 100%) and Muco-adhesion strength of (3510.5 ± 140.21 to 9319.5 ± 39.425). DSC results of S4 and S8 showed compatibility of (ATM) with the other excipients. S8 and S4 also showed higher trans-nasal permeation to the brain with brain targeting efficiency of (211.3% and 177.42%, respectively) and drug transport percentages of (52.7% and 43.64%, respectively). To conclude, lyophilized nasal inserts of (ATM-SLNs) enhanced (ATM) trans-nasal drug targeting permeation and brain targeting efficiency.

Preparation and characterization of zein-lecithin-total flavonoids from Smilax glabra complex nanoparticles and the study of their antioxidant activity on HepG2 cells

Total flavonoids from Smilax glabra (TFSG) exhibit several biological activities; however, their poor stability limits their application. In this work, zein-lecithin-TFSG complex nanoparticles (Z-L-TFSG NPs) were prepared using the anti-solvent coprecipitation technique. The prepared Z-L-TFSG NPs were spherical with an encapsulation efficiency of 98.0%. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and morphology tests revealed that the TFSG were successfully encapsulated by Z-L NPs. Z-L-TFSG NPs showed superior stability and better controlled release characteristics in simulated gastrointestinal digestion. The encapsulation of TFSG by Z-L NPs could improve their antioxidant capacity in vitro. Moreover, Z-L-TFSG NPs could enhance the protective effects of TFSG against H₂O₂-induced oxidative damage to HepG2 cells. The results indicated that the Z-L self-assembled NPs could serve as a promising drug delivery system through the integrated encapsulation of multiple flavonoids.

Enhanced healing efficacy of an optimized gabapentin-melittin nanoconjugate gel-loaded formulation in excised wounds of diabetic rats

The present study aimed to design and optimize, a nanoconjugate of gabapentin (GPN)-melittin (MLT) and to evaluate its healing activity in rat diabetic wounds. To explore the wound healing potency of GPN-MLT nanoconjugate, an in vivo study was carried out. Diabetic rats were subjected to excision wounds and received daily topical treatment with conventional formulations of GPN, MLT, GPN-MLT nanoconjugate and a marketed formula. The outcome of the in vivo study showed an expedited wound contraction in GPN-MLT-treated animals. This was confirmed histologically. The nanoconjugate formula exhibited antioxidant activities as evidenced by preventing malondialdehyde (MDA) accumulation and superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic exhaustion. Further, the nanoconjugate showed superior anti-inflammatory activity as it inhibited the expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). This is in addition to enhancement of proliferation as indicated by increased expression of transforming growth factor-β (TGF- β), vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor receptor-β (PDGFRB). Also, nanoconjugate enhanced hydroxyproline concentration and mRNA expression of collagen type 1 alpha 1 (Col 1A1). In conclusion, a GPN-MLT nanoconjugate was optimized with respect to particle size. Analysis of pharmacokinetic attributes showed the mean particle size of optimized nanoconjugate as 156.9 nm. The nanoconjugate exhibited potent wound healing activities in diabetic rats. This, at least partly, involve enhanced antioxidant, anti-inflammatory, proliferative and pro-collagen activities. This may help to develop novel formulae that could accelerate wound healing in diabetes.

Orally delivered solid lipid nanoparticles of irinotecan coupled with chitosan surface modification to treat colon cancer: Preparation, in-vitro and in-vivo evaluations

Irinotecan-loaded solid lipid nanoparticles (IRI-SLNs) was formulated and tested for its potential activity against colon cancer. IRI-SLNs were prepared by applying the principles of DoE. Nanoparticles were further surface modified using chitosan. Characterizations such as size, poly-dispersity, surface charge, morphology, entrapment, drug release pattern, cytotoxicity were conducted. In-vivo studies in male Wistar rats were carried to ascertain distribution pattern of SLNs and their acute toxicity on various vital organs. Lastly, stability of the SLNs were evaluated. Particles had a size, polydispersity and zeta potential of 430.77 ± 8.69 nm, 0.36 ± 0.02 and -40.06 ± 0.61 mV, respectively. Entrapment of IRI was 62.24 ± 2.90% in IRI-SLNs. Sustained drug release was achieved at a colonic pH and long-term stability of NPs was seen. Cytotoxicity assay results showed that SLNs exhibited toxicity on HCT-116 cells. Biodistribution studies confirmed higher concentration of drug in the colon after surface modification. An acute toxicity study conducted for 7 days showed no severe toxic effects on major organs. Thus, we picture that the developed SLNs may benefit in delivering IRI to the tumour cells, therefore decreasing the dose and dose-associated toxicities.

Brain targeted delivery of rapamycin using transferrin decorated nanostructured lipid carriers

Introduction: Recent studies showed that rapamycin, as a mammalian target of rapamycin (mTOR) inhibitor, could have beneficial therapeutic effects for the central nervous system (CNS) related diseases. However, the immunosuppressive effect of rapamycin as an adverse effect, the low water solubility, and the rapid in vivo degradation along with the blood-brain barrier-related challenges restricted the clinical use of this drug for brain diseases. To overcome these drawbacks, a transferrin (Tf) decorated nanostructured lipid carrier (NLC) containing rapamycin was designed and developed. Methods: Rapamycin-loaded cationic and bare NLCs were prepared using solvent diffusion and sonication method and well characterized. The optimum cationic NLCs were physically decorated with Tf. For in vitro study, the MTT assay and intracellular uptake of nanoparticles on U-87 MG glioblastoma cells were assessed. The animal biodistribution of nanoparticles was evaluated by fluorescent optical imaging. Finally, the in vivo effect of NLCs on the immune system was also studied. Results: Spherical NLCs with small particle sizes ranging from 120 to 150 nm and high entrapment efficiency of more than 90%, showed ≥80% cell viability. More importantly, Tf-decorated NLCs in comparison with bare NLCs, showed a significantly higher cellular uptake (97% vs 60%) after 2 hours incubation and further an appropriate brain accumulation with lower uptake in untargeted tissue in mice. Surprisingly, rapamycin-loaded NLCs exhibited no immunosuppressive effect. Conclusion: Our findings proposed that the designed Tf-decorated NLCs could be considered as a safe and efficient carrier for targeted brain delivery of rapamycin which may have an important value in the clinic for the treatment of neurological disorders.

Mastoparan, a Peptide Toxin from Wasp Venom Conjugated Fluvastatin Nanocomplex for Suppression of Lung Cancer Cell Growth

Lung cancer has a very low survival rate, and non-small cell lung cancer comprises around 85% of all types of lung cancers. Fluvastatin (FLV) has demonstrated the apoptosis and suppression of tumor-cell proliferation against lung cancer cells in vitro. Drug–peptide nanoconjugates were found to enhance the cytotoxicity of anti-cancer drugs. Thus, the present study aimed to develop a nanocomplex of FLV with mastoparan (MAS), which is a peptide that has membranolytic anti-tumor activity. The nanocomplex of FLV and MAS (MAS-FLV-NC) was prepared and optimized for particle size using Box–Behnken design. The amount of FLV had the highest influence on particle size. While higher levels of FLV and incubation time favored higher particle size, a higher level of sonication time reduced the particle size of MAS-FLV-NC. The optimum formula of MAS-FLV-NC used 1.00 mg of FLV and was prepared with an incubation time of 12.1339 min and a sonication time of 6 min. The resultant particle size was 77.648 nm. The in vitro cell line studies of MAS-FLV-NC, FLV, and MAS were carried out in A549 cells. The IC₅₀ values of MAS-FLV-NC, FLV, and MAS were 18.6 ± 0.9, 58.4 ± 2.8, and 34.3 ± 1.6 µg/mL respectively, showing the enhanced cytotoxicity of MAS-FLV-NC. The apoptotic activity showed that MAS-FLV-NC produced a higher percentage of cells in the late phase, showing a higher apoptotic activity than FLV and MAS. Furthermore, cell cycle arrest in S and Pre G1 phases by MAS-FLV-NC was observed in the cell cycle analysis by flow cytometry. The loss of mitochondrial membrane potential after MAS-FLV-NC treatment was significantly higher than those observed for FLV and MAS. The IL-1β, IL-6, and NF-kB expressions were inhibited, whereas TNF-α, caspase-3, and ROS expressions were enhanced by MAS-FLV-NC treatment. Furthermore, the expression levels of Bax, Bcl-2, and p53 strongly established the enhanced cytotoxic effect of MAS-FLV-NC. The results indicated that MAS-FLV-NC has better cytotoxicity than individual effects of MAS and FLV in A549 cells. Further pre-clinical and clinical studies are needed for developing MAS-FLV-NC to a clinically successful therapeutic approach against lung cancer.

Apamin-Conjugated Alendronate Sodium Nanocomplex for Management of Pancreatic Cancer

Pancreatic cancer has a low survival rate and has limited therapeutic options due to the peculiarity of the tumor tissue. Cancer nanotechnology provides several opportunities to resolve such difficulties as a result of the high surface-to-volume ratio of nanostructures. Peptide-drug nanocomplexes have proved to have immense potential in anticancer activity against pancreatic cancer cells. Thus, in the present study apamin (APA) and alendronate sodium (ALS) were combined to form nanocomplexes (APA-ALS-NC) against pancreatic cancer cells. Optimization of ALS, incubation time, and sonication time in terms of particle size of the nanocomplex was carried out. The optimized formulation was evaluated for anticancer activities in pancreatic cancer cells (PANC-1 cells). A Box-Behnken design using ALS, incubation time, and sonication time as independent factors and particle size as the response was chosen to optimize the APA-ALS-NC formulation. The optimized APA-ALS-NC had a particle size of 161.52 ± 8.4 nm. The evaluation of APA-ALS-NC in PANC-1 cells was carried out using various in vitro tests. The IC₅₀ values were determined by MTT assay and found to be 37.6 ± 1.65, 13.4 ± 0.59, and 1.01 ± 0.04 µg/mL for ALS, APA, and APA-ALS-NC, respectively. The higher cytotoxicity activity of APA-ALS-NC was confirmed from the higher percentage of cells in the necrosis phase (apoptosis study) and the G2-M phase (cell cycle study) compared to that of ALS and APA. While the loss of mitochondrial membrane potential was less for APA-ALS-NC, the levels of IL-1β, TNF-α, caspase-3, ROS, IL-6, and NF-kB showed that APA-ALS-NC can significantly enhance apoptosis and cytotoxicity in PANC-1 cells. Moreover, Bax (10.87 ± 1.36), Bcl-2 (0.27 ± 0.02), and p53 (9.16 ± 1.22) gene expressions confirmed that APA-ALS-NC had a significant apoptotic effect compared to ALS and APA. In summary, the APA-ALS-NC had a more significant cytotoxic effect than ALS and APA. The results of the present study are promising for further evaluation in pre-clinical and clinical trials for arriving at a successful therapeutic strategy against pancreatic cancer.

Size shifting of solid lipid nanoparticle system triggered by alkaline phosphatase for site specific mucosal drug delivery

We aim to prepare a size-shifting nanocarrier for site-targeting mucosal drug delivery that can penetrate through mucus gel layer and remain close to the absorption membrane. As nanocarriers can be engineered to penetrate mucus but they can also back diffuse into outer mucus regions, a size shifting to micron range once they have reached the absorption membrane would prevent back-diffusion effect and extend drug release over a long period of time. For this purpose, we loaded solid lipid nanoparticles (SLN) with a phosphate ester surfactant and octadecylamine. Alkaline phosphatase (AP), a membrane bound enzyme was for the first time utilized as an in situ partner for triggering the size conversion at epithelial cell surface. Having the size of ~120 nm, SLN with hydrophilic and phosphate-decorated shells were shown to penetrate through mucus gel and form aggregates above cell layer surface. Aggregates of 5-8 µm were formed due to interparticle interactions induced by enzymatic phosphate removal after ~30 min in contact with isolated AP. The developed SLN system could be a potential tool for mucosal drug delivery to AP-expressing tissues like colon, lung, cervix, vagina and some mucus-secreting tumors.

Quality by Design Adapted Chemically Engineered Lipid Architectonics for HIV Therapeutics and Intervention: Contriving of Formulation, Appraising the In vitro Parameters and In vivo Solubilization Potential

The present research encompasses a quality by design approach for fabricating lipid architectonics (LA) of an antiretroviral drug (Elvitegravir: EVR) to overcome inherent challenges of EVR to curtail its bioavailability issues. Comparative development strategy employing Box-Behnken design was undertaken between high-pressure homogenization technique and melt emulsification followed by probe sonication method, wherein the later was selected for engineering the EVR-LA. Particle size, entrapment efficiency and drug loading for EVR-LA were 84.6 ± 2.3 nm, 90.7 ± 1.8% and 8.9 ± 0.7% respectively. In vitro release studies established the supremacy of EVR-LA when compared with drug suspension (EVR-DS) by having a cumulative drug release of 96.89 ± 2.5% in pH 1.2, 89.84 ± 2.4% in pH 6.8 and 86.64 ± 2.5% in pH 7.4. Gut permeation studies revealed 19-fold increment in permeation by EVR-LA attributable to intrinsic permeation enhancing and efflux protein inhibitory activity of the lipids and surfactants incorporated. The result was validated by confocal study which exhibited enhanced permeation by EVR-LA. Dissolution study, conducted in fasted state simulated intestinal fluid (FaSSIF) and fed state simulated intestinal fluid (FeSSIF) media to ascertain the effect of food, demonstrated boosted absorption from FeSSIF media. Stability study was conducted in SGF pH 1.2, FaSSIF and FeSSIF media. The lipolysis study, conducted to determine in vivo fate of EVR, revealed 27-fold increment in solubilization potential from EVR-LA (72.43 ± 2.6%). Thus, EVR-LA exhibited remarkable in vitro results by improving gut permeation and solubilization fate along with enhanced lymphatic uptake, thereby leading to prospective in vivo fate.

Formulating SLN and NLC as Innovative Drug Delivery Systems for Non-Invasive Routes of Drug Administration

Colloidal carriers diverge depending on their composition, ability to incorporate drugs and applicability, but the common feature is the small average particle size. Among the carriers with the potential nanostructured drug delivery application there are SLN and NLC. These nanostructured systems consist of complex lipids and highly purified mixtures of glycerides having varying particle size. Also, these systems have shown physical stability, protection capacity of unstable drugs, release control ability, excellent tolerability, possibility of vectorization, and no reported production problems related to large-scale. Several production procedures can be applied to achieve high association efficiency between the bioactive and the carrier, depending on the physicochemical properties of both, as well as on the production procedure applied. The whole set of unique advantages such as enhanced drug loading capacity, prevention of drug expulsion, leads to more flexibility for modulation of drug release and makes Lipid-based nanocarriers (LNCs) versatile delivery system for various routes of administration. The route of administration has a significant impact on the therapeutic outcome of a drug. Thus, the non-invasive routes, which were of minor importance as parts of drug delivery in the past, have assumed added importance drugs, proteins, peptides and biopharmaceuticals drug delivery and these include nasal, buccal, vaginal and transdermal routes. The objective of this paper is to present the state of the art concerning the application of the lipid nanocarriers designated for non-invasive routes of administration. In this manner, this review presents an innovative technological platform to develop nanostructured delivery systems with great versatility of application in non-invasive routes of administration and targeting drug release.

Sonochemical synthesis of carbon dots, mechanism, effect of parameters, and catalytic, energy, biomedical and tissue engineering applications

Carbon-based nanomaterials are gaining more and more interest because of their wide range of applications. Carbon dots (CDs) have shown exclusive interest due to unique and novel physicochemical, optical, electrical, and biological properties. Since their discovery, CDs became a promising material for wide range of research applications from energy to biomedical and tissue engineering applications. At same time several new methods have been developed for the synthesis of CDs. Compared to many of these methods, the sonochemical preparation is a green method with advantages such as facile, mild experimental conditions, green energy sources, and feasibility to formulate CDs and doped CDs with controlled physicochemical properties and lower toxicity. In the last five years, the sonochemically synthesized CDs were extensively studied in a wide range of applications. In this review, we discussed the sonochemical assisted synthesis of CDs, doped CDs and their nanocomposites. In addition to the synthetic route, we will discuss the effect of various experimental parameters on the physicochemical properties of CDs; and their applications in different research areas such as bioimaging, drug delivery, catalysis, antibacterial, polymerization, neural tissue engineering, dye absorption, ointments, electronic devices, lithium ion batteries, and supercapacitors. This review concludes with further research directions to be explored for the applications of sonochemical synthesized CDs.

Improved antibacterial function of Rifampicin-loaded solid lipid nanoparticles on Brucella abortus

The objective of this study was to assess the antibacterial activity of Rifampicin-loaded solid lipid nanoparticles on Brucella abortus 544. Rifampicin-loaded solid lipid nanoparticles were prepared by a modified microemulsion/sonication method and characterized. The results showed the average size about 319.7 nm, PI about 0.20 and zeta potential about 18.4 mv, encapsulation efficacy and drug-loading were equal to 95.78 and 34.2%, respectively, with a spherical shape. Drug release lasted for 5 days. The antibacterial activity was statistically significant with p < .05 in bacterial and cell culture media compared to free Rifampicin. It can be concluded that solid lipid nanoparticles can be considered as a promising delivery system for improving the antibacterial activity of Rifampicin against Brucella abortus.

Correlating ultrasonic impulse and addition of ZnO promoter with CO2 conversion and methanol selectivity of CuO/ZrO2 catalysts

The thermal characteristics of Cu-based catalysts for CO₂ utilization towards the synthesis of methanol were analysed and discussed in this study. The preparation process were varied by adopting ultrasonic irradiation at various impulses for the co-precipitation route and also, by introducing ZnO promoters using the solid-state reaction route. Prepared catalysts were characterised using XRD, TPR, TPD, SEM, BET and TG-DTA-DSC. In addition, the CO₂ conversion and CH₃OH selectivity of these samples were assessed. Calcination of the catalysts facilitated the interaction of the Cu catalyst with the respective support bolstering the thermal stability of the catalysts. The characterisation analysis clearly reveals that the thermal performance of the catalysts was directly related to the sonication impulse and heating rate. Surface morphology and chemistry was enhanced with the aid of sonication and introduction of promoters. However, the impact of the promoter outweighs that of the sonication process. CO₂ conversion and methanol selectivity showed a significant improvement with a 270% increase in methanol yield.

Development of solid lipid nanoparticles containing total flavonoid extract from Dracocephalum moldavica L. and their therapeutic effect against myocardial ischemia-reperfusion injury in rats

Total flavonoid extract from Dracocephalum moldavica L. (TFDM) contains effective components of D. moldavica L. that have myocardial protective function. However, the cardioprotection function of TFDM is undesirable due to its poor solubility. In order to improve the solubility and efficacy of TFDM, we developed TFDM-loaded solid lipid nanoparticles (TFDM-SLNs) and optimized the formulation of TFDM-SLNs using central composite design and response surface methodology. The physicochemical properties of TFDM-SLNs were characterized, and the pharmacodynamics was investigated using the myocardial ischemia-reperfusion injury model in rats. The nanoparticles of optimal formulation for TFDM-SLNs were spherical in shape with the average particle size of 104.83 nm and had a uniform size distribution with the polydispersity index value of 0.201. TFDM-SLNs also had a negative zeta potential of -28.7 mV to ensure the stability of the TFDM-SLNs emulsion system. The results of pharmacodynamics demonstrated that both TFDM and TFDM-SLN groups afforded myocardial protection, and the protective effect of TFDM-SLNs was significantly superior to that of TFDM alone, based on the infarct area, histopathological examination, cardiac enzyme levels and inflammatory factors in serum. Due to the optimal quality and the better myocardial protective effect, TFDM-SLNs are expected to become a safe and effective nanocarrier for the oral delivery of TFDM.

Influence of sonophoresis on transdermal drug delivery of hydrophilic compound-loaded lipid nanocarriers

The effect of sonophoresis on the transdermal drug delivery of sodium fluorescein (NaFI)-loaded lipid nanocarriers such as liposomes (LI), niosomes (NI) and solid lipid nanoparticles (SLN) was investigated by confocal laser scanning microscopy (CLSM), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that SN decreased the skin penetration of NaFI-loaded SLN (6.32-fold) and NI (1.79-fold), while it increased the penetration of NaFI-loaded LI (5.36-fold). CLSM images showed the red fluorescence of the LI and NI bilayer on the superficial layer of the stratum corneum. However, the red fluorescent probe of the SLN was not visualized in the skin. FTIR results of the LI and NI with SN showed no effect on lipid stratum corneum ordering, suggesting that the fragment of bilayer vesicles might repair the damaged skin. For SLN, the strengthening of stratum corneum by covering the disrupted skin with solid lipids was shown. SEM images show disrupted carriers of all the formulations adsorbed onto the damaged skin. In conclusion, the SN changed the properties of both the skin surface and lipid nanocarrier, demonstrating that disrupted skin might be repaired by a disrupted nanocarrier.

Lipid nanoparticles for the topical delivery of retinoids and derivatives

Retinoids are lipophilic compounds that are highly used in cosmetics/therapeutics for skin disorders. Conventional formulations are limited by poor water solubility, high chemical/photochemical instability and the irritation of retinoids. Interestingly, lipid nanoparticles enable the administration of retinoids in aqueous media, providing drug stabilization and controlled release. Recently, it has been demonstrated that retinoids in solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions and nanocapsules can decrease degradation, improve targeting and enhance efficacy for the treatment of skin disorders. This article focuses on the formulation, fabrication, characterization and in vitro/in vivo evaluation of solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions and nanocapsules loaded with retinoids for skin administration. Furthermore, the incorporation of these lipid nanoparticles into secondary vehicles is discussed.