Influence of ion pairing on topical delivery of retinoic acid from microemulsions

A preliminary investigation into the use of amino acids as potential ion pairs for diclofenac transdermal delivery

Ion pairing is a potential strategy used to increase the partition and permeation of ionisable drug molecules. This work outlines the process of identifying, selecting and testing potential counter ions for diclofenac (DF). Three screening criteria were considered in the initial selection process. The first, toxicity, was used to eliminate counter ion candidates that could not be used in topical formulations. The second related to the balancing of charges. As DF is a free acid in its unionised state, counter ions should be of a basic character. Finally, molecular size, as represented by molecular mass (Da), was used. Because of the impact on ion pair formation, the counter ion was required to have a lower molecular weight than diclofenac. Basic amino acids L-Arginine, L-Histidine, L-Lysine and their salts were chosen. The selection process concluded with Partition Coefficient (PC) studies. These were used to identify any counter ions able to interact electrostatically with the ionised DF, enabling the 'neutral' ion pair to partition from an aqueous into an organic layer. Permeation studies using porcine skin were performed to test the efficacy of any selected counter ion. These preliminary studies suggest that amino acids may be used as counter ions to increase the partition and permeation of ionisable drugs.

Ion Pairs for Transdermal and Dermal Drug Delivery: A Review

Ion pairing is a strategy used to increase the permeation of topically applied ionised drugs. Formation occurs when the electrostatic energy of attraction between oppositely charged ions exceeds their mean thermal energy, making it possible for them to draw together and attain a critical distance. These ions then behave as a neutral species, allowing them to partition more readily into a lipid environment. Partition coefficient studies may be used to determine the potential of ions to pair and partition into an organic phase but cannot be relied upon to predict flux. Early researchers indicated that temperature, size of ions and dielectric constant of the solvent system all contributed to the formation of ion pairs. While size is important, this may be outweighed by improved lipophilicity of the counter ion due to increased length of the carbon chain. Organic counter ions are more effective than inorganic moieties in forming ion pairs. In addition to being used to increase permeation, ion pairs have been used to control and even prevent permeation of the active ingredient. They have also been used to stabilise solid lipid nanoparticle formulations. Ion pairs have been used in conjunction with permeation enhancers, and permeation enhancers have been used as counter ions in ion pairing. This review attempts to show the various ways in which ion pairs have been used in drug delivery via the skin. It also endeavours to extract and consolidate common approaches in order to inform future formulations for topical and transdermal delivery.

Preparation of cerium-curcumin and cerium-quercetin complexes and their LEDs irradiation assisted anticancer effects on MDA-MB-231 and A375 cancer cell lines

Cancer remains common and often is difficult to eradicate. In particular resistant forms like triple negative breast cancer and melanoma generally allow for very short survival. Curcumin and quercetin as two important polyphenols from plants which have different biological roles, potentially including anti-cancer effect. But their clinical application is limited due to poor solubility in aqueous medium. Photodynamic therapy (PDT) is a cancer treatment using select chemical compounds as photosensitizers, which when activated by light create toxic singlet oxygen. Studies done on plant based photosensitizers such as curcumin and quercetin have shown the ability to ablate tumors. Here we discuss using them as improved PS by making their complex with cerium ions as a delivery system for MDA-MB-231 and A375 cancer cell lines treatment. For this purpose, the MDA-MB-231 human breast cancer cell line exposed to red light irradiation (as pretreatment) then treated with curcumin and quercetin alone and also their complex with cerium. In another study the cells treated with curcumin-cerium and quercetin-cerium complex and then irradiated with blue light (photodynamic treatment). Cell survival and apoptosis were determined using MTT and fluorescence microscopy. The result showed that curcumin and quercetin in complex with cerium ions have better toxic effect against both breast and melanoma cancer cells as compared to each compound alone. The finding revealed that curcumin and quercetin in cerium complex could be considered as a new approach in the photodynamic treatment of breast and melanoma cancer cells.

Increased Therapeutic Efficacy of SLN Containing Etofenamate and Ibuprofen in Topical Treatment of Inflammation

Innovative formulations, including solid lipid nanoparticles (SLNs), have been sought to improve skin permeation of non-steroidal anti-inflammatory drugs (NSAIDs). The present study explores the use of SLNs, prepared using a fusion-emulsification method, to increase skin permeation and in vivo activity of two relevant NSAIDs: A liquid molecule (etofenamate) and a solid one (ibuprofen), formulated in a 2% hydroxypropyl methylcellulose gel through the gelation of SLN suspensions. Compritol^® 888 ATO and Tween^® 80 were used as a solid lipid and a surfactant, respectively. All production steps were up scalable, resulting in SLNs with high encapsulation efficiency (>90%), a mean particle size of <250 nm, a polydispersity index <0.2, and that were stable for 12 months. In vitro permeation, using human skin in Franz diffusion cells, showed increased permeation and similar cell viability in Df and HaCaT cell lines for SLN formulations when compared to commercial formulations of etofenamate (Reumon^® Gel 5%) and ibuprofen (Ozonol^® 5%). In vivo activity in the rat paw edema inflammation model showed that SLN hydrogels containing lower doses of etofenamate (8.3 times lower) and ibuprofen (16.6 times lower) produced similar effects compared to the commercial formulations, while decreasing edema and inflammatory cell infiltration, and causing no histological changes in the epidermis. These studies demonstrate that encapsulation in SLNs associated to a suitable hydrogel is a promising technological approach to NSAIDs dermal application.

The Design of Anionic Surfactant-Based Amino-Functionalized Mesoporous Silica Nanoparticles and their Application in Transdermal Drug Delivery

Melanoma remains the most lethal form of skin cancer and most challenging to treat despite advances in the oncology field. Our work describes the utilization of nanotechnology to target melanoma locally in an attempt to provide an advanced and efficient quality of therapy. Amino-functionalized mesoporous silica nanoparticles (MSN-NH₂) were developed in situ through the utilization of anionic surfactant and different volumes of 3-aminopropyltriethoxysilane (APTES) as a co-structure directing agent (CSDA). Prepared particles were characterized for their morphology, particles size, 5-flurouracol (5-FU) and dexamethasone (DEX) loading capacity and release, skin penetration, and cytotoxicity in vitro in HT-144 melanoma cells. Results of transmission electron microscopy (TEM) and nitrogen adsorption-desorption isotherm showed that using different volumes of APTES during the functionalization process had an impact on the internal and external morphology of the particles, as well as particle size. However, changing the volume of APTES did not affect the diameter of formed mesochannels, which was about 4 nm. MSN-NH₂ showed a relatively high loading capacity of 5-FU (12.6 ± 5.5) and DEX (44.72 ± 4.21) when using drug: MSN-NH₂ ratios of 5:1 for both drugs. The release profile showed that around 83% of 5-FU and 21% of DEX were released over 48 h in pH 7.4. The skin permeability study revealed that enhancement ratio of 5-Fu and DEX using MSN-NH₂ were 4.67 and 5.68, respectively, relative to their free drugs counterparts. In addition, the accumulation of drugs in skin layers where melanoma cells usually reside were enhanced approximately 10 times with 5-FU and 5 times with DEX when delivering drugs using MSN-NH₂ compared to control. MSN-NH₂ alone was nontoxic to melanoma cells when incubated for 48 h in the range of 0 to 468 µg/mL. The combination of 5-FU MSN-NH₂ and DEX MSN-NH₂ showed significant increase in toxicity compared to their free dug counterparts and exhibited a synergetic effect as well as the ability to circumvent DEX induced 5-FU resistance in melanoma cells.

Ion-pair approach coupled with nanoparticle formation to increase bioavailability of a low permeability charged drug

Atenolol is a drug widely used for the treatment of hypertension. However, the great drawback it presents is a low bioavailability after oral administration. To obtain formulations that allow to improve the bioavailability of this drug is a challenge for the pharmaceutical technology. The objective of this work was to increase the rate and extent of intestinal absorption of atenolol as model of a low permeability drug, developing a double technology strategy. To increase atenolol permeability an ion pair with brilliant blue was designed and the sustained release achieved through encapsulation in polymeric nanoparticles (NPs). The in vitro release studies showed a pH-dependent release from NPs, (particle size 437.30 ± 8.92) with a suitable release profile of drug (atenolol) and counter ion (brilliant blue) under intestinal conditions. Moreover, with the in vivo assays, a significant increase (2-fold) of atenolol bioavailability after administering the ion-pair NPs by oral route was observed. In conclusion, the combination of ion-pair plus polymeric NPs have proved to be a simple and very useful approach to achieve a controlled release and to increase the bioavailability of a low permeability charged drugs.

Biomedical applications of microemulsion through dermal and transdermal route

Microemulsions are thermodynamically stable, transparent, colloidal drug carrier system extensively used by the scientists for effective drug delivery across the skin. It is a spontaneous isotropic mixture of lipophilic and hydrophilic substances stabilized by suitable surfactant and co-surfactant. The easy fabrication, long-term stability, enhanced solubilization, biocompatibility, skin-friendly appearance and affinity for both the hydrophilic and lipophilic drug substances make it superior for skin drug delivery over the other carrier systems. The topical administration of most of the active compounds is impaired by limited skin permeability due to the presence of skin barriers. In this sequence, the microemulsion represents a cost-effective and convenient drug carrier system which successfully delivers the drug to and across the skin. In the present review work, we compiled various attempts made in last 20 years, utilizing the microemulsion for dermal and transdermal delivery of various drugs. The review emphasizes the potency of microemulsion for topical and transdermal drug delivery and its effect on drug permeability.

Graphene oxide-methylene blue nanocomposite in photodynamic therapy of human breast cancer

The interaction of methylene blue (MB) as a photosensitizer with graphene oxide nano-sheets (GO) was examined in aqueous solution using UV-vis spectrophotometric techniques. MB-GO composites were prepared by mixing the solutions of GO nano-sheets and methylene blue due to interacting of the cationic methylene blue photosensitizer via electrostatic and π-π stacking or hydrophobic cooperative interactions. The cell killing potential of nanocomposite was examined on the MDA-MB-231 breast cancer cells in the absence and presence of red LED irradiation. The results demonstrated that the MB-GO nanocomposite has good performance in photodynamic therapy (PDT) during red LED irradiation. The cytotoxicity of nanocomposite caused reducing cell viability up to 20%. These effects would be due to the nano size structure of composite that could lead to effective cellular penetration. Also the significant difference has seen in lower concentrations of MB and MB-GO nanocomposite. The results show more than 40% increases in cell killing potential in lower concentrations of nanocomposite by using 2.5 μg/mL of each compound. The ratio of GO/MB can affect the interaction and higher ratios of graphene oxide (GO/MB > 1) can induce dimerization of MB. In lower concentrations and ratios of (GO/MB < 1) the free MB concentration increases and the electron shuttling effect of GO in photo activity decreases - which could affect the photocatalytic yield in PDT. The cell viability measurements confirm these effects on cancer cell killing potential of nanocomposite. According to microscopic and PDT assay results, the nanocomposite distribution and diffusion in cells enhanced the photochemical reaction yield in photodynamic therapy of MDA-MB-231 breast cancer cell line.

Methylene blue, curcumin and ion pairing nanoparticles effects on photodynamic therapy of MDA-MB-231 breast cancer cell

PURPOSE

The aim of current study was to use methylene blue-curcumin ion pair nanoparticles and single dyes as photosensitizer for comparison of photodynamic therapy (PDT) efficacy on MDA-MB-231 cancer cells, also various light sources effect on activation of photosensitizer (PS) was considered.

METHOD

Ion pair nanoparticles were synthesized using opposite charge ions precipitation and lyophilized. The PDT experiments were designed and the effect of PSs and light sources (Red LED (630nm; power density: 30mWcm^-2) and blue LED (465nm; power density: 34mWcm^-2)) on the human breast cancer cell line were examined. The effect of PS concentration (0-75μg.mL^-1), incubation time, irradiation time and light sources, and priority in irradiation of blue or red lights were determined.

RESULTS

The results show that the ion pairing of methylene blue and curcumin enhance the photodynamic activity of both dyes and the cytotoxicity of ion pair nanoparticles on the MDA-231 breast cancer cell line. Blue and red LED light sources were used for photo activation of photosensitizers. The results demonstrated that both dyes can activate using red light LED better than blue light LED for singlet oxygen producing.

CONCLUSION

Nano scale ion pair precipitating of methylene blue-curcumin enhanced the cell penetrating and subsequently cytotoxicity of both dyes together.

Current and evolving approaches for improving the oral permeability of BCS Class III or analogous molecules

The Biopharmaceutics Classification System (BCS) classifies pharmaceutical compounds based on their aqueous solubility and intestinal permeability. The BCS Class III compounds are hydrophilic molecules (high aqueous solubility) with low permeability across the biological membranes. While these compounds are pharmacologically effective, poor absorption due to low permeability becomes the rate-limiting step in achieving adequate bioavailability. Several approaches have been explored and utilized for improving the permeability profiles of these compounds. The approaches include traditional methods such as prodrugs, permeation enhancers, ion-pairing, etc., as well as relatively modern approaches such as nanoencapsulation and nanosizing. The most recent approaches include a combination/hybridization of one or more traditional approaches to improve drug permeability. While some of these approaches have been extremely successful, i.e. drug products utilizing the approach have progressed through the USFDA approval for marketing; others require further investigation to be applicable. This article discusses the commonly studied approaches for improving the permeability of BCS Class III compounds.

Lipase-Sensitive Transfersomes Based on Photosensitizer/Polymerizable Lipid Conjugate for Selective Antimicrobial Photodynamic Therapy of Acne

Acne vulgaris is a common skin problem affecting nearly 90% of adolescents and its development is associated with a colonization of Propionibacterium acnes (P. acnes). Although antibiotics have commonly been used to treat acne, antibiotic resistance of P. acnes is an emerging issue to be solved. In this study, a new way of photodynamic acne therapy is developed using P. acnes lipase-sensitive transfersome (DSPE-PEG-Pheo A (DPP) transfersome). For enhanced selectivity and skin penetration efficiency, DPP transfersomes are prepared from 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000], pheophorbide A (Pheo A), cholesterol, and Tween-80. Incorporation of Tween-80 as an edge activator increases the deformability of DPP transfersomes, enhancing skin penetration efficiency to four times that of free Pheo A. The photoactivity of Pheo A quenched by DPP transfersomes is gradually recovered by selective cleavage of the ester linkage in DPP transfersomes by P. acnes lipases. In vitro P. acnes-specific photoactivity and subsequent selective antimicrobial effect exhibit a greater than 99% loss of P. acnes viability. In vivo antiacne therapeutic effect is confirmed by reduction of swelling volume and thickness of P. acnes-induced nude mice skin. These results demonstrate that DPP transfersome-mediated photodynamic therapy can be used as an alternative method to treat bacterial skin infections.

Synthesis, characterization and in vitro evaluation of amphiphilic ion pairs of erythromycin and kanamycin antibiotics with liposaccharides

The hydrophilic ion paring strategy (HIP) is a method explored to improve the cell/tissue uptake of poorly adsorbed drugs and to optimize their physico-chemical characteristics. In this context, we here describe the synthesis of some ion pairs of two model cationic antibiotics, erythromycin (ERY) and kanamycin A (KAN), with liposaccharides having different levels of lipophilicity and charge. The formation of drug-liposaccharide complexes was confirmed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) analysis. The effect of the amphiphilic liposaccharide moieties on the antimicrobial activity of ERY and KAN was assessed by measuring the minimal inhibitory concentration (MIC) of the compounds against a panel of bacterial strains that were susceptible or resistant to the parent antibiotics. The ion pairing did not depress the in vitro antibiotic activity, although no lowering of MIC values was registered. The experimental findings would motivate the future investigation of this ion pairing strategy in drug design, for instance allowing improvement of the encapsulation efficiency of hydrophilic antibiotics in lipid-based nanocarriers, or changing their in vivo biodistribution and pharmacokinetic profile.

A synergistic approach of adapalene-loaded nanostructured lipid carriers, and vitamin C co-administration for treating acne

The present study documents the fabrication and characterization of a topically applicable gel loaded with nanostructured lipid carriers (NLCs) of adapalene (ADA) and vitamin C (ascorbyl-6-palmitate [AP]). The NLCs were prepared by high pressure homogenization (HPH) method followed by incorporation into AP loaded gel. The fabricated system was characterized for size, poly dispersity index, entrapment efficiency (EE) and in vitro drug release properties, and was further investigated for skin compliance, skin transport characteristics (skin permeation and bio-distribution), rheological behavior, texture profile analysis and anti-acne therapeutic potential against testosterone-induced acne in male Wistar rats. The NLC-based formulation improved targeting of the skin epidermal layer and reducing systemic penetration. The co-administration of vitamin C led to an adjunct effect in acne therapy in physiological conditions. In brief, the present results suggest the potential of NLCs as a novel carrier for the dermal delivery of ADA and also the synergistic effect of vitamin C in topical therapeutics.

Adapalene loaded solid lipid nanoparticles gel: an effective approach for acne treatment

Salient features such as controlled release, target ability, potential of penetration, improved physical stability, low cost compared to phospholipids, and ease of scaling-up makes solid lipid nanoparticles (SLNs) a viable alternative to liposomes for effective drug delivery. Adapalene (ADA) is a second generation retinoid effective in treating various dermatologic disorders such as Acne vulgaris with a few noticeable dose-mediated side effects. The present study was aimed at developing and characterizing ADA loaded SLNs for effective topical delivery. The formulated SLN system was characterized for particle size, poly dispersity index, entrapment efficiency and drug release properties. The resultant formulation (ADA loaded SLNs incorporated into carbopol hydrogel) was evaluated for in vitro drug release, skin permeation and bio-distribution, rheological behaviour, and texture profile analysis. The SLNs based ADA gel has shown its potential in targeting skin epidermal layer, and reducing systemic penetration. The developed system can avoid systemic uptake of ADA in skin layers, and can localize drug in skin epidermis as confirmed by rat skin model. Our results advocate potential of SLNs as a novel carrier for topical delivery of ADA in topical therapeutic approaches. This study open new avenues for drug delivery which better meets the need of anti-acne research.

New perspectives on antiacne plant drugs: contribution to modern therapeutics

Acne is a common but serious skin disease, which affects approximately 80% adolescents and young adults in 11-30 age group. 42.5% of men and 50.9% of women continue to suffer from this disease into their twenties. Bacterial resistance is now at the alarming stage due to the irrational use of antibiotics. Hence, search for new lead molecule/bioactive and rational delivery of the existing drug (for better therapeutic effect) to the site of action is the need of the hour. Plants and plant-derived products have been an integral part of health care system since time immemorial. Therefore, plants that are currently used for the treatment of acne and those with a high potential are summarized in the present review. Most active plant extracts, namely, P. granatum, M. alba, A. anomala, and M. aquifolium exhibit minimum inhibitory concentration (MIC) in the range of 4-50 µg/mL against P. acnes, while aromatic oils of C. obovoides, C. natsudaidai, C. japonica, and C. nardus possess MICs 0.005-0.6 μL/mL and phytomolecules such as rhodomyrtone, pulsaquinone, hydropulsaquinone, honokiol, magnolol, xanthohumol lupulones, chebulagic acid and rhinacanthin-C show MIC in the range of 0.5-12.5 μg/mL. Novel drug delivery strategies of important plant leads in the treatment of acne have also been discussed.

Carrier-based drug delivery system for treatment of acne

Approximately 95% of the population suffers at some point in their lifetime from acne vulgaris. Acne is a multifactorial disease of the pilosebaceous unit. This inflammatory skin disorder is most common in adolescents but also affects neonates, prepubescent children, and adults. Topical conventional systems are associated with various side effects. Novel drug delivery systems have been used to reduce the side effect of drugs commonly used in the topical treatment of acne. Topical treatment of acne with active pharmaceutical ingredients (API) makes direct contact with the target site before entering the systemic circulation which reduces the systemic side effect of the parenteral or oral administration of drug. The objective of the present review is to discuss the conventional delivery systems available for acne, their drawbacks, and limitations. The advantages, disadvantages, and outcome of using various carrier-based delivery systems like liposomes, niosomes, solid lipid nanoparticles, and so forth, are explained. This paper emphasizes approaches to overcome the drawbacks and limitations associated with the conventional system and the advances and application that are poised to further enhance the efficacy of topical acne formulations, offering the possibility of simplified dosing regimen that may improve treatment outcomes using novel delivery system.

Nano-lipoidal carriers of isotretinoin with anti-aging potential: formulation, characterization and biochemical evaluation

BACKGROUND

Treatment of photoaging includes non-prescription cosmeceuticals and prescription products, retinoids. Isotretinoin, an established anti-acne retinoid, is also reported to delay the aging process. However, the drug is reported to be an irritant on skin.

PURPOSE

The present study endeavors to explore the potential of a novel set of biocompatible nano-structured systems of isotretinoin in the treatment of photoaging.

METHODS

Nano-lipoidal carriers (NLCs) of isotretinoin were developed, characterized and investigated in vivo for anti-aging potential in Laca mice vis-à-vis the marketed products of retinoids. The anti-aging efficacy of NLCs was measured in terms of visual and redox-biochemical parameters in ultraviolet (UV)-irradiated mice.

RESULTS

Visual observations revealed that there was no significant change (p < 0.05) w.r.t. erythema, skin sagging and wrinkles in the skin of the animals treated with NLCs formulation compared to the marketed product(s). The malondialdehyde levels were found to be significantly reduced, whereas glutathione levels were increased with the application of NLCs vis-à-vis control and test formulations. The NLCs were able to maintain the normal redox-balance of UV-irradiated skin, and were better tolerated by the animals.

CONCLUSION

The study ratifies enhancement in the efficacy of isotretinoin against photoaging and improved skin biocompatibility after its encasement in novel topical dosage forms.

Transdermal delivery of an anti-cancer drug via w/o emulsions based on alkyl polyglycosides and lecithin: design, characterization, and in vivo evaluation of the possible irritation potential in rats

The purpose of this work was to develop w/o emulsions that could be safely used to promote transdermal delivery of 5-fluorouracil (5-FU). Two pseudo-ternary phase diagrams comprising oleoyl-macrogol glycerides, water, and a surfactant/co-surfactant (S/CoS) mixture of lecithin, ethanol, and either coco glucoside or decyl glucoside were investigated for their potential to develop promising 5-FU emulsions. Six systems were selected and subjected to thermodynamic stability tests; heat-cool cycles, centrifugation, and finally freeze-thaw cycles. All systems passed the challenges and were characterized for transmission electron microscopy, droplet size, rheological behavior, pH, and transdermal permeation through newly born mice skin in Franz diffusion cells. The systems had spherical droplets ranging in diameter from 1.81 to 2.97 μm, pH values ranging from 7.50 to 8.49 and possessed Newtonian flow. A significant (P<0.05) increase in 5-FU permeability parameters as steady-state flux, permeability coefficient was achieved with formula B5 comprising water (5% w/w), S/CoS mixture of lecithin/ethanol/decyl glucoside (14.67:12.15:18.18% w/w, respectively) and oleoyl-macrogol glycerides (50% w/w). When applied to shaved rat skin, this system was well tolerated with only moderate skin irritation that was recovered within 12 h. Indeed, minor histopathologic changes were observed after 5-day treatment. Further studies should be carried out, in the future, to investigate the potentiality of this promising system to promote transdermal delivery of 5-FU through human skin.

An investigation into the influence of binary drug solutions upon diffusion and partition processes in model membranes

Few studies have assessed the impact of binary systems on the fundamental mathematical models that describe drug permeation. The aim of this work was to determine the influence of varying the proportions of prilocaine and lidocaine in a binary saturated solution on mass transfer across synthetic membranes. Infinite-dose permeation studies were performed using Franz diffusion cells with either regenerated cellulose or silicone membranes, and partition coefficients were determined by drug loss over 24 h. There was a linear relationship between the flux of prilocaine and lidocaine through regenerated cellulose membrane (R2 ≥ 0.985, n = 5) and their normalised ratio in solution. This linear model was also applicable for the permeation of prilocaine through silicone membrane (R2 = 0.991, n = 5), as its partition coefficient was independent of the drug ratio (15.84 ± 1.41). However, the partition coefficient of lidocaine increased from 27.22 ± 1.68 to 47.03 ± 3.32 as the ratio of prilocaine increased and this resulted in a non-linear relationship between permeation and drug ratio. Irrespective of the membrane used, the permeation of one drug from a binary system was hindered by the presence of the second, which could be attributed to a reduction in available membrane diffusion volume.

Desenvolvimento e validação de método analítico em CLAE-UV para a quantificação de ácido retinóico em microcápsulas de alginato e quitosana

O ácido retinóico (AR) tem sido utilizado para o tratamento de acne severa, rugas, estrias e celulite, no entanto, provoca irritação na pele e sofre rápida degradação quando exposto à luz e ao calor. Métodos analíticos rápidos para quantificação do AR são, portanto, necessários para ensaios de cinética de liberação in vitro. Nesse contexto, o objetivo deste trabalho foi desenvolver e validar um método rápido e sensível para o doseamento do AR em microcápsulas de alginato/quitosana contendo óleo de babaçu dispersas em gel natrosol® por cromatografia líquida de alta eficiência associada à espectroscopia UV e aplicá-lo na avaliação do perfil de liberação in vitro dessas formulações. As análises foram realizadas em modo isocrático utilizando coluna C18 de fase reversa 150 x 4,6 mm (5 μm) com detecção a 350 nm. A fase móvel foi constituída de metanol e ácido acético 1% (85:15 v/v) com vazão de 1,8 mL/minuto. A faixa de linearidade do método foi de 0,5 a 60 μg/mL (r² = 0,999). O método validado mostrou-se sensível, específico, exato, preciso, de baixo custo e o tempo de retenção do AR foi de 5,8 ± 0,4 minutos sendo, desta forma, mais rápido do que os relatados na literatura.

Effect of Oil Phase Lipophilicity on In Vitro Drug Release from O/W Microemulsions with Low Surfactant Content

In this work we investigated the effects of oil phase lipophilicity on in vitro drug release from topical o/w microemulsions (MEs) containing low percentages of emulsifiers. Three different lipids, isopropyl myristate (IPM), isopropyl palmitate (IPP), and isopropyl stearate (IPS), whose lipophilicity increased in the order IPM < IPP <IPS, were used as oil phase to prepare o/w MEs containing low amounts (7.7% w/w) of two surfactant/cosurfactant mixtures, isoceteth-20/glyceryl oleate (5:2) (MEs 1-3) and oleth-20/glyceryl oleate (5:2) (MEs 4-6). All the MEs were prepared using the phase inversion temperature (PIT) method. Three active compounds (0.5% w/w), Naproxen (NAP), Idebenone (IDE), and Butylmethoxydibenzoylmethane (BMBM), were selected as model drugs and their release rates from PIT MEs were evaluated using Franz-type diffusion cells. All the MEs gave a mean droplet diameter ranging from 28 to 44 nm and showed a single peak in size distribution. The addition of IDE to MEs 1-6 did not significantly change ME droplet size. On the contrary, an increase of the droplet size beyond the ME limit (150 nm) was observed when isoceteth-20 was used as surfactant to prepare MEs containing NAP or MEs containing BMBM and IPS as oil phase. Pseudo-first order release rates were observed only for NAP from MEs 1-3, while MEs containing IDE showed an initial slow release followed by an increased release of the test compound. The release rate constants were found to be dependent on the ME composition and on the active compound incorporated. The highest release rate was observed from ME 1 containing IPM as oil phase and NAP as drug. As regards BMBM, its release rate was not calculated since no release was observed until 6 h from the beginning of the experiment. The cumulative amount of active compound released after 22 h was inversely related to drug lipophilicity (NAP Log P = 2,9; IDE Log P 3,5; BMBM Log P 4,8). These findings could be attributable to a reduced thermodynamic activity of the drugs in the vehicles containing the most lipophilic oil phase due to an increase of drug solubility which could lead to an unfavorable drug partition from the oil phase. The results of this study suggest that the choice of proper combinations of oil phase lipids and emulsifiers may allow achieving drug controlled delivery from topical o/w MEs with low emulsifier content.

Microemulsions--modern colloidal carrier for dermal and transdermal drug delivery

Microemulsions are modern colloidal drug carrier systems. They form spontaneously combining appropriate amounts of a lipophilic and a hydrophilic ingredient, as well as a surfactant and a co-surfactant. Due to their special features, microemulsions offer several advantages for pharmaceutical use, such as ease of preparation, long-term stability, high solubilization capacity for hydrophilic and lipophilic drugs, and improved drug delivery. The article summarizes the level of research with respect to dermal and transdermal application. A large number of in vitro as well as some in vivo studies demonstrated that drugs incorporated into microemulsions penetrate efficiently into the skin. The enhancing activity seems to be attributable to a variety of factors depending on the composition and the resulting microstructure of the formulations. However, an extended use in practice depends on the choice of well-tolerated ingredients, mainly surfactants, and the restriction of their amounts in order to guarantee skin compatibility.

Development of lapachol topical formulation: anti-inflammatory study of a selected formulation

This study aimed at developing a topical formulation of lapachol, a compound isolated from various Bignoniaceae species and at evaluating its topical anti-inflammatory activity. The influence of the pharmaceutical form and different types of emulsifiers was evaluated by in-vitro release studies. The formulations showing the highest release rate were selected and assessed trough skin permeation and retention experiments. It was observed that the gel formulation provided significantly higher permeation and retained amount (3.9-fold) of lapachol as compared to the gel-cream formulation. Antinociceptive and antiedematogenic activities of the most promising formulation were also evaluated. Lapachol gel reduced the increase in hind-paw volume induced by carrageenan injection and reduced nociception produced by acetic acid (0.8% in water, i.p.) when used topically. These results suggest that topical delivery of lapachol from gel formulations may be an effective medication for both dermal and subdermal injuries.

Development of a new solid lipid nanoparticle formulation containing retinoic acid for topical treatment of acne

The development of solid lipid nanoparticles (SLN) containing all-trans retinoic acid (RA) is an interesting approach to topical treatment of acne. SLN has potential for controlled release and follicular penetration, which can reduce adverse effects in comparison with conventional formulations. However, the encapsulation efficiency (EE) of RA in SLN is usually low, unless a high surfactant/lipid ratio is used. The aim of this work was to develop SLN with high EE using a low surfactant/lipid ratio. Different formulations of RA-loaded SLN were prepared using glyceryl behenate as lipid matrix. The particle size, EE, zeta potential and differential scanning calorimetry (DSC) were investigated. High EE in SLN was obtained with addition of amines. These results indicate that the utilization of amines is an interesting approach to improve the EE of RA in SLN using a low surfactant/lipid ratio.

Isotretinoin-loaded solid lipid nanoparticles with skin targeting for topical delivery

The purpose of this study was to construct isotretinoin-loaded SLN (IT-SLN) formulation with skin targeting for topical delivery of isotretinoin. PRECIROL ATO 5 was selected as the lipid of SLN. Tween 80 and soybean lecithin were used as the surfactants to stabilize SLN. The hot homogenization method was performed to prepare the drug-loaded SLN. The various formulations were characterized by photon correlation spectroscopy and all the SLN formulations had low average size between 30 and 50 nm. Transmission electron microscopy studies showed that the IT-SLN formulation had a spherical shape. All the formulations had high entrapment efficiency ranging from 80% to 100%. The penetration of isotretinoin from the IT-SLN formulations through skins and into skins were evaluated in vitro using Franz diffusion cells fitted with rat skins. The in vitro permeation data showed that all the IT-SLN formulations can avoid the systemic uptake of isotretinoin in skins, however the control tincture had a permeation rate of 0.76+/-0.30 microg cm(-2)h(-1) through skins. The IT-SLN consisting of 3.0% PRECIROL ATO 5, 4.0% soybean lecithin and 4.5% Tween 80 could significantly increased the accumulative uptake of isotretinoin in skin and showed a significantly enhanced skin targeting effect. The studied IT-SLN showed a good stability. These results indicate that the studied IT-SLN formulation with skin targeting may be a promising carrier for topical delivery of isotretinoin.

Microemulsions as transdermal drug delivery vehicles

Microemulsions are clear, stable, isotropic mixtures of oil, water, and surfactant, frequently in combination with a cosurfactant. Microemulsions have been intensively studied during the last decades by many scientists and technologists because of their great potential in many food and pharmaceutical applications. The use of microemulsions is advantageous not only due to the facile and low cost preparation, but also because of the improved bioavailability. The increased absorption of drugs in topical applications is attributed to enhancement of penetration through the skin by the carrier. Saturated and unsaturated fatty acids serving as an oil phase are frequently used as penetration enhancers. The most popular enhancer is oleic acid. Other permeation enhancers commonly used in transdermal formulations are isopropyl myristate, isopropyl palmitate, triacetin, isostearylic isostearate, R(+)-limonene and medium chain triglycerides. The most popular among the enhancing permeability surfactants are phospholipids that have been shown to enhance drug permeation in a different mode. l-alpha-phosphatidylcholine from egg yolk, l-alpha-phosphatidylcholine 60%, from soybean and dioleylphosphatidyl ethanolamine which are in a fluid state may diffuse into the stratum corneum and enhance dermal and transdermal drug penetration, while distearoylphosphatidyl choline which is in a gel-state has no such capability. Other very commonly used surfactants are Tween 20, Tween 80, Span 20, Azone, Plurol Isostearique and Plurol Oleique. As cosurfactants commonly serve short-chain alkanols such as ethanol and propylene glycol. Long-chain alcohols, especially 1-butanol, are known for their enhancing activity as well. Decanol was found to be an optimum enhancer among other saturated fatty alcohols that were examined (from octanol to myristyl alcohol). Many enhancers are concentration-dependent; therefore, optimal concentration for effective promotion should be determined. The delivery rate is dependent on the type of the drug, the structure and ingredients of the carrier, and on the character of the membrane in use. Each formulation should be examined very carefully, because every membrane alters the mechanism of penetration and can turn an enhancer to a retarder. Various potential mechanisms to enhance drug penetration through the skin include directly affecting the skin and modifying the formulation so the partition, diffusion, or solubility is altered. The combination of several enhancement techniques such as the use of iontophoresis with fatty acids leads to synergetic drug penetration and to decrease in skin toxicity. Selected studies of various microemulsions containing certain drugs including retinoic acid, 5-fluorouracil, triptolide, ascorbic acid, diclofenac, lidocaine, and prilocaine hydrochloride in transdermal formulations are presented in this review. In conclusion, microemulsions were found as an effective vehicle of the solubilization of certain drugs and as protecting medium for the entrapped of drugs from degradation, hydrolysis, and oxidation. It can also provide prolonged release of the drug and prevent irritation despite the toxicity of the drug. Yet, in spite of all the advantages the present formulations lack several key important characteristics such as cosmetic-permitted surfactants, free dilution in water capabilities, stability in the digestive tracts and sufficient solubilization capacity.

Niosomes as carriers for tretinoin. III. A study into the in vitro cutaneous delivery of vesicle-incorporated tretinoin

The influence of drug thermodynamic activity and niosome composition, size, lamellarity and charge on the (trans)dermal delivery of tretinoin (TRA) was studied. For this purpose, tretinoin was incorporated at saturated and unsaturated concentrations in both multilamellar (MLV) and unilamellar (UV) vesicular formulations using two different commercial mixtures of alkyl polyglucosides: octyl-decyl polyglucoside and decyl polyglucoside. Positively and negatively charged vesicular formulations were prepared using either stearylamine or dicetylphosphate as a charge inducer. Niosomes made with polyoxyethylene (4) lauryl ether and liposomes made with soy phosphatidylcholine were also prepared and studied. Vesicular formulations were characterised by transmission electron microscopy and optical and light polarized microscopy for vesicle formation and morphology, and by dynamic laser light scattering for size distribution. The effect of the vesicular incorporation of tretinoin on its (trans)dermal delivery through the newborn pig skin was also investigated in vitro using Franz cells, in comparison with a commercial formulation of the drug (RetinA). The amount of tretinoin delivered through and accumulated in the several skin layers was detected by HPLC. Overall, obtained results showed that tretinoin cutaneous delivery is strongly affected by vesicle composition and thermodynamic activity of the drug. In particular, small, negatively charged niosomal formulations, which are saturated with tretinoin, have shown to give higher cutaneous drug retention than both liposomes and commercial formulation. Moreover, interactions between skin and vesicles seem to depend on physico-chemical properties of the main component of the vesicular bilayer.

Podophyllotoxin-loaded solid lipid nanoparticles for epidermal targeting

The purpose of this study was to evaluate solid lipid nanoparticles as the topical carrier for epidermal targeting of podophyllotoxin (POD). The high pressure homogenization was employed to prepare drug-loaded solid lipid nanoparticles. The POD-loaded SLN stabilized by 0.5% poloxamer 188 and 1.5% soybean lecithin (P-SLN) and 2% polysorbate 80 (T-SLN) was characterized by photon correlation spectroscopy (PCS). P-SLN showed an average diameter of 73.4 nm and a zeta potential of -48.36 mV. The imaging of AFM indicated that the P-SLN had a spherical shape. DSC and X-ray diffraction analysis showed that POD was dispersed in SLN in an amorphous state. The in vitro permeation study showed that P-SLN increased the accumulative amount of POD in porcine skin 3.48 times over 0.15% tincture. But T-SLN with a diameter of 123.1 nm and a zeta potential of -17.4 mV did not show a high accumulative amount of POD when compared with P-SLN, though both P-SLN and T-SLN could avoid the systemic uptake of POD. Because of the fluorescence property of POD, fluorescence microscopy imaging was employed to visualize the penetration of POD into skin from SLN. The penetration of POD from P-SLN seemed to follow two pathways along the stratum corneum and hair follicle route. The imaging revealed that P-SLN had a strong localization of POD within epidermis. The penetration of P-SLN with low particle size into stratum corneum along the skin surface 'furrow' and the consequent controlled release of POD might lead to the epidermal targeting. P-SLN provides a good epidermal targeting effect and may be a promising carrier for topical delivery of POD.

Enhanced Delivery of Retinoic Acid to Skin by Cationic Liposomes

We studied the delivery of retinoic acid to skin by using cationic liposomes consisting of double-chained cationic surfactant, phosphatidylcholine (PC) and retinoic acid in excised guinea pig dorsal skin. Egg yolk PC liposomes contaning retinoic acid at a molar ratio of 4 : 1 increased the delivery of retinoic acid about two-fold, compared with its addition as an isopropyl myristate solution. Cationic liposomes containing 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) further enhanced the incorporation dependent on the DOTAP content. Liposomes consisting of DOTAP, egg yolk PC, and retinoic acid at a molar ratio of 2 : 2 : 1 induced a 3.7-fold increase in the skin incorporation compared with the egg yolk PC liposomes without DOTAP. Significant difference was not observed when either dimyristoylphosphatidylcholine (DMPC) or dipalmitoylphosphatidylcholine (DPPC) was used instead of egg yolk PC as well as when dimethyldipalmitylammonium was used instead of DOTAP. These results suggest the potential of the use of the cationic liposomes for the intradermal delivery of lipophilic drugs like retinoic acid.

Novel Drug Delivery Systems: Potential in Improving Topical Delivery of Antiacne Agents

Acne is the most common cutaneous disorder of multifactorial origin with a prevalence of 70-85% in adolescents. The majority of the acne sufferers exhibit mild to moderate acne initially, which progresses to the severe form in certain cases. Topical therapy is employed as first-line treatment in mild acne, whereas for moderate and severe acne, systemic therapy is required in addition to topical therapy. Currently, several topical agents are available that affect at least one of the main pathogenetic factors responsible for the development of acne. Although topical therapy has an important position in acne treatment, side effects associated with various topical antiacne agents and the undesirable physicochemical characteristics of certain important agents like tretinoin and benzoyl peroxide affect their utility and patient compliance. Novel drug delivery strategies can play a pivotal role in improving the topical delivery of antiacne agents by enhancing their dermal localization with a concomitant reduction in their side effects. The current review emphasizes the potential of various novel drug delivery strategies like liposomes, niosomes, aspasomes, microsponges, microemulsions, hydrogels and solid lipid nanoparticles in optimizing and enhancing the topical delivery of antiacne agents.

Phase behavior of the microemulsions and the stability of the chloramphenicol in the microemulsion-based ocular drug delivery system

Microemulsion systems composed of Span20/80+Tween20/80+n-butanol+H2O+isopropyl palmitate (IPP)/isopropyl myristate (IPM) were investigated as model systems of drug carriers for eye drops. Effects of chloramphenicol, normal saline, sodium hyaluronate and various oils on the phase behavior were studied. The phase transition was investigated by the electrical conductivity measurements. The electrical conductivity of the microemulsion was affected by the encapsulation of the drug into the system, and the addition of normal saline and sodium hyaluronate. The chloramphenicol is used to treat the diseases such as trachoma and keratitis. However, this drug in the common eye drops hydrolyzes easily. The main product of the hydrolysis is glycols. Here, the chloramphenicol was trapped into the oil-in-water (o/w) microemulsions and its stability was investigated by the high performance liquid chromatography (HPLC) assays in the accelerated experiments of 3 months. Its location in the microemulsion formulations was determined by means of 1H NMR spectroscopy. The results of HPLC revealed that the contents of the glycols in the microemulsion formulations were much lower than that in the commercial eye drops at the end of the accelerated experiments. It implied that the stability of the chloramphenicol in the microemulsion formulations was increased remarkably. The NMR experiments confirmed that the chloramphenicol molecules should be trapped into the hydrophilic shells of the microemulsion drops, which was composed of many oxyethylene groups. The nitro-groups of the chloramphenicol molecules were near the alpha2-CH2 of the surfactant molecules and the benzene rings of the chloramphenicol molecules were near the oxyethylene groups of the surfactant molecules. It was this reason that enabled the chloramphenicol molecules in the microemulsions to be screened from the bulk water and its stability to be increased remarkably.