Formulation and clinical evaluation of silymarin pluronic-lecithin organogels for treatment of atopic dermatitis

Relieving postherpetic neuralgia pain via gabapentin-loaded bigels as an auspicious topical drug delivery system

BACKGROUND

Over the past decades, a substantial portion of the population worldwide has been infected with varicella zoster and most cases developed shingles. Unfortunately, shingles is usually accompanied by postherpetic neuralgia, which may persist for months to years after the resolution of the viral infection.

OBJECTIVES

Gabapentin is an orally gamma-aminobutyric acid analogue approved by the Food and Drug Administration to manage shingles postherpetic neuralgia. However, gabapentin shows nonlinear pharmacokinetics, with variable absorption and bioavailability along with its short half-life and long side effects that may include dizziness and somnolence, which calls for an appropriate topical dosage form. Bigels are unique semisolid dosage forms with boosted penetrability and satisfactory hydrophilic texture.

METHODS

The current work pointed to formulating gabapentin-loaded bigels for the treatment of postherpetic neuralgia, where the analysis and optimization of design were performed via Design-Expert®.

RESULTS AND CONCLUSIONS

The selected bigel (F5), incorporating 400 mg Span 60, 1000 mg Tween 80, and 1000 mg Transcutol, displayed spherical nanosized particles with acceptable viscosity and spreadability. Subsequent topical application of the selected bigel on the skin of Wistar rats, F5, demonstrated a boosted accumulation of gabapentin in the skin similar to PLO gel but superior to the drug solution. Furthermore, a histopathological study demonstrated the biosafety of the selected bigel when applied topically. Accordingly, gabapentin-loaded bigel would be considered a potentially topical dosage form for the delivery of gabapentin for the management of postherpetic neuralgia.

Quality by design optimization of formulation variables and process parameters for enhanced transdermal delivery of nanosuspension

This investigation aims to fabricate, characterize, and optimize organogel containing andrographolide nanosuspension to enhance transdermal drug delivery into and across the skin in vitro. We identified the critical material attributes (CMAs) and critical process parameters (CPPs) that impact key characteristics of andrographolide nanosuspension using a systematic quality-by-design approach. We prepared andrographolide nanosuspension using the wet milling technique and evaluated various properties of the formulations. The CMAs were types and concentrations of polymers, types and concentrations of surfactants, drug concentration, and lipid concentration. The CPPs were volume of milling media and milling duration. Mean particle size, polydispersity index, encapsulation efficiency, and drug loading capacity as critical quality attributes were selected in the design for the evaluation and optimization of the formulations. Furthermore, we developed and evaluated organogel formulation to carry andrographolide nanosuspension 0.05% w/w. Drug release and permeation studies were conducted to assess the drug release kinetics and transdermal delivery of andrographolide. We presented the alteration in the average particle size, polydispersity index, encapsulation efficiency, drug-loading capacity, and drug release among various formulations to select the optimal parameters. The permeation study indicated that organogel delivered markedly more drug into the receptor fluid and skin tissue than DMSO gel (n = 3, p < 0.05). This enhancement in transdermal drug delivery was demonstrated by cumulative drug permeation after 24 h, steady-state flux, permeability coefficient, and predicted steady-state plasma concentration. Drug quantity in skin layers, total delivery, delivery efficiency, and topical selectivity were also reported. Conclusively, andrographolide nanosuspension-loaded organogel significantly increased transdermal drug delivery in vitro.

Nitric Oxide-Releasing Topical Treatments for Cutaneous Melanoma

Melanoma is an aggressive skin cancer notorious for high levels of drug resistance. Additionally, current treatments such as immunotherapies are often associated with numerous adverse side effects. The use of nitric oxide (NO) may represent an attractive treatment for melanoma due to NO's various anticancer properties, unlikeliness to foster resistance, and limited toxicity toward healthy tissues. The anticancer effects of chemical NO donors have been explored previously but with limited understanding of the needed characteristics for exerting optimal antimelanoma activity. Herein, the in vitro therapeutic efficacy of three macromolecular NO donor systems (i.e., cyclodextrin, mesoporous silica nanoparticles, and hyaluronic acid) with tunable NO-release kinetics was explored by evaluating skin permeation along with toxicity against melanoma and healthy skin cells. Cytotoxicity against melanoma cells was dependent on NO payload and not donor identity or NO-release kinetics. In contrast, cytotoxicity against healthy cells was primarily influenced by the macromolecular NO donor, with cyclodextrin- and hyaluronic acid-based NO donors having the highest therapeutic indices. In vitro skin permeation was influenced by both the size and charge of the NO donor, with smaller, more neutral donors resulting in greater permeation. A Pluronic F127 organogel was optimized for the delivery of a cyclodextrin-based NO donor. Delivery of the NO donor in this manner resulted in increased in vitro skin permeation and reduced tumor growth in an in vivo model.

Lecithin Organogel: A Promising Carrier for the Treatment of Skin Diseases

Skin is the largest organ of the human body, as it protects the body from the external environment. Nowadays, skin diseases and skin problems are more common, and millions of people are affected daily. Skin diseases are due to numerous infectious pathogens or inflammatory conditions. The increasing demand for theoretical research and practical applications has led to the rising prominence of gel as a semisolid material. To this end, organogels has been widely explored due to their unique composition, which includes organic solvents and mineral or vegetable oils, among others. Organogels can be described as semisolid systems wherein an organic liquid phase is confined within a three-dimensional framework consisting of self-assembled, cross-linked, or entangled gelator fibers. These gels have the ability to undergo significant expansion and retain substantial amounts of the liquid phase, reaching up to 99% swelling capacity. Furthermore, they respond to a range of physical and chemical stimuli, including temperature, light, pH, and mechanical deformation. Notably, due to their distinctive properties, they have aroused significant interest in a variety of practical applications. Organogels favor the significant encapsulation and enhanced permeation of hydrophobic molecules when compared with hydrogels. Accordingly, organogels are characterized into lecithin organogels, pluronic lecithin organogels, sorbitan monostearate-based organogels, and eudragit organogels, among others, based on the nature of their network and the solvent system. Lecithin organogels contain lecithin (natural and safe as a living cell component) as an organogelator. It acts as a good penetration enhancer. In this review, first we have summarized the fundamental concepts related to the elemental structure of organogels, including their various forms, distinctive features, methods of manufacture, and diverse applications. Nonetheless, this review also sheds light on the delivery of therapeutic molecules entrapped in the lecithin organogel system into deep tissue for the management of skin diseases and provides a synopsis of their clinical applications.

Hypothesizing the Oleic Acid-Mediated Enhanced and Sustained Transdermal Codelivery of Pregabalin and Diclofenac Adhesive Nanogel: A Proof of Concept

Pregabalin (PG) and diclofenac diethylamine (DEE) are anti-inflammatory molecules that are effective in relieving inflammation and pain associated with musculoskeletal disorders, arthritis, and post-traumatic pain, among others. Intravenous and oral delivery of these two molecules has their limitations. However, the transdermal route is believed to be an alternate viable option for the delivery of therapeutic molecules with desired physicochemical properties. To this end, it is vital to understand the physicochemical properties of these drugs, dosage, and strategies to enhance permeation, thereby surmounting the associated constraints and concurrently attaining a sustained release of these therapeutic molecules when administered in combination. The present work hypothesizes the enhanced permeation and sustained release of pregabalin and diclofenac diethylamine across the skin, entrapped in the adhesive nano-organogel formulation, including permeation enhancers. The solubility studies of pregabalin and diclofenac diethylamine in combination were performed in different permeation enhancers. Oleic acid was optimized as the best permeation enhancer based on in vitro studies. Pluronic organogel containing pregabalin and diclofenac diethylamine with oleic acid was fabricated. Duro-Tak® (87-2196) was added to the organogel formulation as a pressure-sensitive adhesive to sustain the release profile of these two therapeutic molecules. The adhesive organogel was characterized for particle size, scanning electron microscopy, and contact angle measurement. The HPLC method developed for the quantification of the dual drug showed a retention time of 3.84 minutes and 9.69 minutes for pregabalin and diclofenac, respectively. The fabricated nanogel adhesive formulation showed the desired results with particle size and contact angle of 282 ± 57 nm and ≥120⁰, respectively. In vitro studies showed the percentage cumulative release of 24.90 ± 4.65% and 33.29 ± 4.81% for pregabalin and diclofenac, respectively. In order to accomplish transdermal permeation, the suggested hypothesis of fabricating PG and DEE nano-organogel in combination with permeation enhancers will be a viable drug delivery method. In comparison to a traditional gel formulation, oleic acid as a permeation enhancer increased the penetration of both PG and DEE from the organogel formulation. Notably, the studies showed that the use of pressure-sensitive adhesives enabled the sustained release of both PG and DEE.Therefore, the results anticipated the hypothesis that the transdermal delivery of adhesive PG and DEEbased nanogel across the human skin can be achieved to inhibit inflammation and pain.

Poloxamer-based nanogels as delivery systems: how structural requirements can drive their biological performance?

Poloxamers or Pluronics®-based nanogels are one of the most used matrices for developing delivery systems. Due to their thermoresponsive and flexible mechanical properties, they allowed the incorporation of several molecules including drugs, biomacromolecules, lipid-derivatives, polymers, and metallic, polymeric, or lipid nanocarriers. The thermogelling mechanism is driven by micelles formation and their self-assembly as phase organizations (lamellar, hexagonal, cubic) in response to microenvironmental conditions such as temperature, osmolarity, and additives incorporated. Then, different biophysical techniques have been used for investigating those structural transitions from the mechanisms to the preferential component's orientation and organization. Since the design of PL-based pharmaceutical formulations is driven by the choice of the polymer type, considering its physico-chemical properties, it is also relevant to highlight that factors inherent to the polymeric matrix can be strongly influenced by the presence of additives and how they are able to determine the nanogels biopharmaceuticals properties such as bioadhesion, drug loading, surface interaction behavior, dissolution, and release rate control. In this review, we discuss the general applicability of three of the main biophysical techniques used to characterize those systems, scattering techniques (small-angle X-ray and neutron scattering), rheology and Fourier transform infrared absorption spectroscopy (FTIR), connecting their supramolecular structure and insights for formulating effective therapeutic delivery systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01093-2.

Monoketonic Curcuminoid-Lidocaine Co-Deliver Using Thermosensitive Organogels: From Drug Synthesis to Epidermis Structural Studies

Organogels (ORGs) are remarkable matrices due to their versatile chemical composition and straightforward preparation. This study proposes the development of ORGs as dual drug-carrier systems, considering the application of synthetic monoketonic curcuminoid (m-CUR) and lidocaine (LDC) to treat topical inflammatory lesions. The monoketone curcuminoid (m-CUR) was synthesized by using an innovative method via a NbCl₅–acid catalysis. ORGs were prepared by associating an aqueous phase composed of Pluronic F127 and LDC hydrochloride with an organic phase comprising isopropyl myristate (IPM), soy lecithin (LEC), and the synthesized m-CUR. Physicochemical characterization was performed to evaluate the influence of the organic phase on the ORGs supramolecular organization, permeation profiles, cytotoxicity, and epidermis structural characteristics. The physico-chemical properties of the ORGs were shown to be strongly dependent on the oil phase constitution. Results revealed that the incorporation of LEC and m-CUR shifted the sol-gel transition temperature, and that the addition of LDC enhanced the rheological G′/G″ ratio to higher values compared to original ORGs. Consequently, highly structured gels lead to gradual and controlled LDC permeation profiles from the ORG formulations. Porcine ear skin epidermis was treated with ORGs and evaluated by infrared spectroscopy (FTIR), where the stratum corneum lipids were shown to transition from a hexagonal to a liquid crystal phase. Quantitative optical coherence tomography (OCT) analysis revealed that LEC and m-CUR additives modify skin structuring. Data from this study pointed ORGs as promising formulations for skin-delivery.

The Influence of Tea Tree Oil on Antifungal Activity and Pharmaceutical Characteristics of Pluronic® F-127 Gel Formulations with Ketoconazole

Fungal skin infections are currently a major clinical problem due to their increased occurrence and drug resistance. The treatment of fungal skin infections is based on monotherapy or polytherapy using the synergy of the therapeutic substances. Tea tree oil (TTO) may be a valuable addition to the traditional antifungal drugs due to its antifungal and anti-inflammatory activity. Ketoconazole (KTZ) is an imidazole antifungal agent commonly used as a treatment for dermatological fungal infections. The use of hydrogels and organogel-based formulations has been increasing for the past few years, due to the easy method of preparation and long-term stability of the product. Therefore, the purpose of this study was to design and characterize different types of Pluronic^® F-127 gel formulations containing KTZ and TTO as local delivery systems that can be applied in cases of skin fungal infections. The influence of TTO addition on the textural, rheological, and bioadhesive properties of the designed formulations was examined. Moreover, the in vitro release of KTZ, its permeation through artificial skin, and antifungal activity by the agar diffusion method were performed. It was found that obtained gel formulations were non-Newtonian systems, showing a shear-thinning behaviour and thixotropic properties with adequate textural features such as hardness, compressibility, and adhesiveness. Furthermore, the designed preparations with TTO were characterized by beneficial bioadhesive properties. The presence of TTO improved the penetration and retention of KTZ through the artificial skin membrane and this effect was particularly visible in hydrogel formulation. The developed gels containing TTO can be considered as favourable formulations in terms of drug release and antifungal activity.

Olive Oil/Pluronic Oleogels for Skin Delivery of Quercetin: In Vitro Characterization and Ex Vivo Skin Permeability

The main objective of this study was to prepare and characterize oleogel as potential carrier for quercetin skin delivery. The formulations were prepared by adding olive oil (5-30%) to Pluronic F127 hydrogel and were evaluated for particle size, zeta potential, viscosity in vitro quercetin release and stability, and were compared with that of Pluronic F127 hydrogel. The selected formulation was characterized for its interaction possibility, ex vivo skin permeation and skin histological changes and safety. The particle sizes ranged from 345.3 ± 5.3 nm to 401.5 ± 2.8 nm, and possessed negative charges. The viscosities of the formulations were found in the range of 6367-4823 cps with inverse proportionality to olive oil percentage while the higher percentages showed higher quercetin release. Percentages of 25% and 30% olive oil showed instability pattern under the conditions of accelerated stability studies. Differential scanning calorimetry verified the existence of quercetin in micellar aggregation and the network in the case of hydrogel and oleogel respectively. Ex vivo skin permeation showed an improved skin permeation of quercetin when 20% olive oil containing oleogel was used. Skin histology after 10 days of application showed stratum corneum disruption and good safety profile. Based on these findings, the proposed oleogel containing 20% olive oil denotes a potential carrier for topical delivery of quercetin.

An Overview of Crucial Dietary Substances and Their Modes of Action for Prevention of Neurodegenerative Diseases

Neurodegenerative diseases, namely Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis are becoming one of the main health concerns due to the increasing aging of the world's population. These diseases often share the same biological mechanisms, including neuroinflammation, oxidative stress, and/or protein fibrillation. Recently, there have been many studies published pointing out the possibilities to reduce and postpone the clinical manifestation of these deadly diseases through lifelong consumption of some crucial dietary substances, among which phytochemicals (e.g., polyphenols) and endogenous substances (e.g., acetyl-L-carnitine, coenzyme Q10, n-3 poysaturated fatty acids) showed the most promising results. Another important issue that has been pointed out recently is the availability of these substances to the central nervous system, where they have to be present in high enough concentrations in order to exhibit their neuroprotective properties. As so, such the aim of this review is to summarize the recent findings regarding neuroprotective substances, their mechanisms of action, as well as to point out therapeutic considerations, including their bioavailability and safety for humans.

Formulation Strategies for Enhancing the Bioavailability of Silymarin: The State of the Art

Silymarin, a mixture of flavonolignan and flavonoid polyphenolic compounds extractable from milk thistle (Silybum marianum) seeds, has anti-oxidant, anti-inflammatory, anti-cancer and anti-viral activities potentially useful in the treatment of several liver disorders, such as chronic liver diseases, cirrhosis and hepatocellular carcinoma. Equally promising are the effects of silymarin in protecting the brain from the inflammatory and oxidative stress effects by which metabolic syndrome contributes to neurodegenerative diseases. However, although clinical trials have proved that silymarin is safe at high doses (>1500 mg/day) in humans, it suffers limiting factors such as low solubility in water (<50 μg/mL), low bioavailability and poor intestinal absorption. To improve its bioavailability and provide a prolonged silymarin release at the site of absorption, the use of nanotechnological strategies appears to be a promising method to potentiate the therapeutic action and promote sustained release of the active herbal extract. The purpose of this study is to review the different nanostructured systems available in literature as delivery strategies to improve the absorption and bioavailability of silymarin.

Immunomodulatory effects of silymarin after subacute exposure to mice: A tiered approach immunotoxicity screening

Silymarin is a flavonoid complex extracted from the Silybum marianum plant with a wide range of pharmacological and biochemical effects. In the present study, the immunomodulatory effects of silymarin were investigated in BALB/c mice. Silymarin was administered daily by intraperitoneal injection at doses of 50, 100 and 150 mg/kg for 14 consecutive days. Following the exposure, host hematological parameters, spleen cellularity and histopathological examination, as well as delayed-type hypersensitivity (DTH) responses, hemagglutination titers (HA), splenocyte cytokine production and lymphocyte proliferation assay were studied in all of the test groups of animals. The results showed that the low dose of silymarin (50 mg/kg) could stimulate both cellular and humoral immune functions in the treated hosts. In addition, silymarin at 100 mg/kg appeared to impact on DTH responses and lymphoproliferation. Based on the finding here, it would seem that silymarin has efficient immunostimulant properties. As a recommendation, the application of silymarin along with acupuncture technique (herbal acupuncture) can be thought as a good plan to modulate and enhance the immune system for the management of several immunodeficiency disorders. However, further studies are required to demonstrate this hypothesis.

Anti-Parkinson Potential of Silymarin: Mechanistic Insight and Therapeutic Standing

Parkinson’s disease (PD) involves aggregation of α-synuclein and progressive loss of dopaminergic neurons. Pathogenesis of PD may also be related to one’s genetic background. PD is most common among geriatric population and approximately 1–2% of population suffers over age 65 years. Currently no successful therapies are in practice for the management of PD and available therapies tend to decrease the symptoms of PD only. Furthermore, these are associated with diverse range of adverse effects profile. The neuroprotective effects of polyphenols are widely studied and documented. Among phytochemicals, silymarin is one of the most widely used flavonoids because of its extensive therapeutic properties and has been indicated in pathological conditions of prostate, CNS, lungs, skin, liver, and pancreas. Silymarin is a mixture of flavonolignans (silybin, isosilybin, and silychristin), small amount of flavonoids (taxifolin), fatty acids, and other polyphenolic compounds extracted from the dried fruit of Silybum marianum and is clinically used for hepatoprotective effects since ancient times. Neuroprotective effects of silymarin have been studied in various models of neurological disorders such as Alzheimer’s disease, PD, and cerebral ischemia. The aim of the present study is to provide a comprehensive review of the recent literature exploring the effects of silymarin administration on the progression of PD. Reducing oxidative stress, inflammatory cytokines, altering cellular apoptosis machinery, and estrogen receptor machinery are mechanisms that are responsible for neuroprotection by silymarin, as discussed in this review. Additionally, because of poor aqueous solubility, the bioavailability of silymarin is low and only 23–47% of silymarin reaches systemic circulation after oral administration. Our primary focus is on the chemical basis of the pharmacology of silymarin in the treatment of PD and its mechanisms and possible therapeutic/clinical status while addressing the bioavailability limitation.

Studies on radiation sensitization efficacy by silymarin in colon carcinoma cells

Recent reports demonstrated the role of silymarin as a cytoprotective agent for normal cells against ionizing or non-ionizing (UV) radiation, and in inhibiting the chemically initiated or promoted carcinogenesis in several malignancies, such as skin or prostate cancers. Silymarin is a plant flavonoid obtained from milk thistle; the main active principles in milk thistle are silybin (silibinin), sylichrisitin and silydianin, commonly referred as silymarin. In the present study, we aimed to investigate the radiation modulatory effects of silymarin on cancer cells. For this, we used the HCT-15 and RKO colon cancer cell lines as a model. Pre-irradiation treatment of cells with silymarin (20 mg/ml) followed by radiation exposure inhibits colon cancer cell proliferation and enhances cell death in a time-dependent manner. We have also examined the changes in p53 phosphorylation at Ser15, phosphorylation of p38 and their association with DNA damage. Silymarin was found to reduce proliferation of the human colon carcinoma cells in a concentration and time-dependent manner. Moreover, percentage of cell death was also increased in combined treatment (20µg/ml of silymarin + radiation). Our studies indicate that the combination increases the arrest of cells in G2/M phase of cell cycle, DNA damage-induced decrease in mitochondrial membrane potential (MMP) and a decrease of the reactive oxygen species (ROS) levels, which are associated with an increase in cell death. Altogether, these results suggest that silymarin sensitizes colon cancer cells to radiation, strategy with potential for colon cancer treatment. Noteworthy, since silymarin was previously shown to confer protection against radiation in at least some types of normal tissues, additional studies are needed to further investigate the potential of silymarin in colon cancer therapy when combined with radiation, its potential protective effects on normal tissues and its mechanisms of action.