Transdermal Delivery of Compounds with Different Lipophilicity and Molecular Weight from W/O Microemulsions Analyzed by UPLC-QTOF/ MS and LC-MS/MS.

OBJECTIVE: The aim of this study was to develop a novel W/O microemulsion for a natural extract of Wen-Luo-Tong (WLT) containing mainly icariin, hydroxysafflor yellow A (HSYA) and gallic acid to be applied to skin as a potential treatment for peripheral neuropathy. METHODS: The oil phase was selected on the basis of affinity with the surfactant and co-surfactant. Pseudo-ternary diagrams were constructed to optimize microemulsions and finally stability studies were performed on the selected formulations. Droplet sizes were analyzed by using a zetasizer and were found to be within the desired range. Selected microemulsions with acceptable viscosities, containing 5%, 8% and 10% of water extract solution, were used for in vitro skin penetration studies using Franz diffusion cells and excised rat skin. New LC-MS/MS and UPLC-Q-TOF/MS methods were employed for quantitative and qualitative analysis. RESULTS: The optimized formulation (ME-4) consisting of 10% (w/w) water extract solution, 60% isopropyl myristate, 30%(w/w) Smix: Propylene glycol (5:2) significantly increased the cumulative permeated amounts of HSYA, icariin and gallic acid compared with the water extract solution controls. CONCLUSION: This novel formulation also increased the number of components penetrating rat skin. Ten components were detected in the Franz cell receptor solution using a UPLC-Q-TOF/MS system after the application of formulation ME-4 for 24h on the skin in vitro. However, only one component was detected after applying the control. Therefore, the microemulsion ME-4 was selected for future in vivo pharmacodynamic studies.

Development, Characterization and Skin Interaction of Capsaicin-Loaded Microemulsion-Based Nonionic Surfactant.

The aim of this study was to develop novel microemulsions (MEs) for the transdermal delivery of capsaicin. Microemulsion-based nonionic surfactants consisting of isopropyl myristate as the oil phase, various nonionic surfactants as the surfactant (S), various glycols or alcohol as the co-surfactant (CoS), and reverse osmosis water as the aqueous phase were formulated. Based on the optimal ME obtained from Design Expert, MEs containing a fixed concentration of oil, water or surfactant were prepared while varying the amounts of the other two fractions. The results indicated that the skin permeation flux of low dose capsaicin (0.15% (w/w)) was significantly higher for the selected ME than the commercial product and capsaicin in ethanol (control) by approximately two- and four-fold, respectively. We successfully demonstrated the feasibility of the transdermal delivery of capsaicin-loaded ME using a low concentration of nonionic surfactant and ethanol. Moreover, the optimization using computer program helped to simplify the development of a pharmaceutical product.

In vitro CPC retention and VSC adsorption by IPM oil droplets: possible mechanisms of action of a two phase mouthwash.

Two phase oil-water mouthwash has been previously shown to efficiently bind oral microorganisms, relying on their cell surface hydrophobicity. The aim of the present in vitro study was to test the cetylpyridinium chloride (CPC) retention and volatile sulfide compounds (VSCs) adsorption abilities of the oil droplets created by mixing of a two phase oil-water solution. VSC adsorption was assayed using a salivary incubation assay and garlic powder solutions, and demonstrated using microscopic sulfide assay. CPC retention was assayed by kinetic and endpoint measurement of Streptococcus salivarius outgrowth using microplate (ELISA) reader. Results showed that the isopropyl myristate (IPM) oil droplets in the two phase solutions were able to adsorb 68-80% of VSCs. CPC at a concentration of 0.05% was most affectively retained by the oil droplets showing a significantly increase in residual antibacterial activity against Streptococcus salivarius. These results taken together, suggests that VSC adsorption and CPC retention by IPM oil droplets may be two additional mechanisms in the activity of the two phase mouthwash formulation.

Preparation and evaluation of andrographolide-loaded microemulsion.

Andrographolide has a low aqueous solubility and oral bioavailability, which limits its clinical application. Reform the dosage forms of andrographolide to improve its aqueous solubility and oral bioavailability. The formulation, characterisation, stability, anti-inflammatory effect, pharmacokinetics and oral toxicity of andrographolide-loaded microemulsion, were studied. An formulation of O/W microemulsion consisting of an oil phase of isopropyl myristate, a surfactant phase of Tween 80, a co-surfactant of alcohol, and water was found to be ideal, with mean droplet size of 15.9 nm, a high capacity of solubilisation for andrographolide (8.02 mg mL(-1)). Such an andrographolide-loaded microemulsion is stable by monitoring the time, temperature and gravity-dependent change, and has a much better anti-inflammatory effect and a higher biological availability than andrographolide tablets. Besides, it also shows a very low acute oral toxicity. The andrographolide-loaded microemulsion is a promising dosage form of andrographolide.

Synergistic effect of isopropyl myristate and glyceryl monocaprylate on the skin permeation of pentazocine.

The aim of this investigation was to assess the applicability of lipid bilayer alteration using a combination of isopropyl myristate (IPM) and glyceryl monocaprylate (GEFA-C(8)) to the enhancement of pentazocine (PTZ) permeation through hairless mouse skin. The skin permeability of PTZ was enhanced by increasing the concentration of GEFA-C(8) up to 10% w/w in combination with IPM. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and small angle X-ray diffraction (SAXD) were carried out to analyze the effects of these enhancers on the biophysical properties of the stratum corneum (SC) of the skin, and on the permeation of PTZ. ATR-FTIR studies revealed that IPM/GEFA-C(8) induced higher CH(2) stretching frequencies of SC lipids than IPM alone. SAXD showed the disappearance of long lamellar diffraction of SC lipids with IPM/GEFA-C(8), resulting in a complete loss of order of the SC lipid bilayers. When 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI), a hydrophobic fluorescence probe, was applied in IPM alone, the amount of DiI which penetrated into the intercellular space of the SC was very low, but this was markedly increased when DiI was applied in IPM/GEFA-C(8). These results indicate that the synergistic effects of IPM and GEFA-C(8) enhance transdermal permeation of PTZ by disrupting SC lipids.

Myristic acid-conjugated polyethylenimine for brain-targeting delivery: in vivo and ex vivo imaging evaluation.

To investigate the potential of myristic acid (MC) to mediate brain delivery of polyethylenimine (PEI) as a gene delivery system, a covalent conjugate (MC-PEI) of MC, and PEI was synthesized. A near-infrared fluorescence probe, IR820 was conjugated to MC-PEI to explore its in vivo distribution after intravenous (i.v.) administration in mice. The brain targeting ability of MC-PEI was evaluated by near-infrared fluorescence imaging and analyzed semiquantitatively by fluorescence intensity, respectively. Significant NIR fluorescent signal was detected in the brain 12 h after i.v. administration and further confirmed by imaging the whole brain and brain slices. Semiquantitative results from fluorescence intensity further supported the successful brain delivery of MC-PEI which led to a very significant increase ( approximately 200%) in the brain uptake after i.v. injection in comparison with unmodified PEI. The capability of MC-PEI to condense DNA was further confirmed using agarose gel retardation assay, indicating its potential for gene delivery. The significant in vivo and ex vivo results suggest that MC-PEI is a promising brain-targeting drug delivery system, especially for gene delivery.

A combined approach of chemical enhancers and sonophoresis for the transdermal delivery of tizanidine hydrochloride.

The effects of chemical enhancers and sonophoresis on the transdermal permeation of tizanidine hydrochloride (TIZ) across mouse skin were investigated. Parameters including drug solubility, apparent partition coefficient (APC), drug permeation, and degradation in skin were determined. Low frequency ultrasound was also applied in the presence and absence of chemical enhancers to assess whether drug permeation improved. APC values indicated that TIZ preferentially partitions into intercellular spaces and does not form a reservoir, with the drug also exhibiting good enzymatic stability in skin. Most of the enhancers studied significantly increased the permeation rate of TIZ through full thickness mouse skin in comparison with TIZ formulated in phosphate buffer. Maximum enhancement was observed for TIZ formulated as a suspension in 50% v/v aqueous ethanol containing 5% v/v citral. Sonophoresis significantly (p < 0.05) increased the cumulative amount of TIZ permeating through the skin at 15 and 30 min in comparison to passive diffusion. A synergistic effect was noted when sonophoresis was applied in the presence of chemical enhancers. The results suggest that the formulation of TIZ with an appropriate penetration enhancer may be useful in the development of a therapeutic system to deliver TIZ across the skin for a prolonged period, i.e. 24 hr. The application of ultrasound in association with chemical enhancers, such as the combination of 5% v/v citral in 50% v/v aqueous ethanol, could further serve as a non-oral and non-invasive drug delivery modality for the immediate therapeutic effect of muscle relaxants such as TIZ.

Beta-cryptoxanthin from citrus juices: assessment of bioaccessibility using an in vitro digestion/Caco-2 cell culture model.

Beta-Cryptoxanthin (beta-CX), a provitaminic carotenoid of potential interest for health, is found principally in Citrus fruit in both free and esterified forms. Little is known about the intestinal absorption of beta-CX especially with regard to the esterified forms. The aim of this study was to evaluate the absorption of free and esterified beta-CX using simulated digestion coupled with the Caco-2 model. Bioaccessibility was investigated by measuring the transfer of carotenoids from different citrus juices into micelles using an in vitro digestion system. Then, carotenoid uptake was evaluated by adding carotenoid-rich micelles (from the in vitro digestion) or synthetic micelles (made from synthetic lipids and carotenoids purified from citrus juice) to human intestinal cells (Caco-2 TC7 clone). Our results showed that beta-cryptoxanthin esters (beta-CXE) were partially hydrolysed during the in vitro digestion. The bioaccessibility of free beta-CX measured was significantly higher (40 (SD 1.05) %) than that of beta-carotene (30 (SD 1.9) %) and beta-CXE (16 (SD 1.5) %). In the same way, the incorporation of free beta-CX (27 (SD 1.01) %) into synthetic micelles exceeded (P<0.05) that of beta-carotene (10 (SD 0.7) %) and beta-CXE (8.8 (SD 0.4) %). In the case of micelles from in vitro digestion, the uptake of beta-carotene, free beta-CX and beta-CXE forms by Caco-2 cells was 14.3 (SD 1.8), 3.9 (SD 1.3), and 0.7 (SD 0.08) % respectively. These results showed a preferential uptake by Caco-2 cells of beta-carotene and free beta-CX compared with the two esters of beta-CX.

The enhancing effect of a triethanolamine-ethanol-isopropyl myristate mixed system on the skin permeation of acidic drugs.

The effect of a TEI enhancer mixed system consisting of triethanolamine (T), ethanol (E) and isopropyl myristate (IPM) on the skin permeation of acidic, basic and neutral drugs were evaluated in vitro using excised hairless rat skin. The binary enhancer system consisting of IPM and ethanol (El) produced marked improvement on the penetration of all the drugs tested. When T was added to the EI system, a greater enhancing effect was found only on acidic drugs with a carboxyl group, compared with the flux in the EI system. On addition of another amine to the EI system, instead of T, mefenamic acid (MA), which exhibited the highest enhancing effect of the model drugs, showed an approximately 14-180 times greater flux than when delivered by the EI system. On simultaneous application of isosorbide dinitrate (ISDN) with MA in the TEI system, the flux of MA increased on increasing the T concentration in the TEI system, while, the flux of ISDN, a neutral drug, was unaffected by the T concentration. Application of MA in the EI system after pretreatment of the TEI system showed that the residual amount of T in the skin plays an important role in the skin permeation of MA. Furthermore, at a fixed concentration of MA, the flux of MA increased on increasing the T concentration in the TEI system, while the flux of E remained unchanged. Finally, the infrared spectrum of MA with amine in the E solution indicated that the carboxyl group of MA was ionized. These results demonstrated that the formation of an ion pair between MA and T, but not the effect of T on the skin, may be responsible for the enhanced skin permeation of MA using the TEI system.

Prediction of transdermal flux of prodrugs of 5-fluorouracil, theophylline, and 6-mercaptopurine with a series/parallel model.

Multiple regression analysis of fluxes from suspensions in isopropyl myristate (J(M)) as a function of molecular weights (MW) and solubilities in isopropyl myristate (S(IPM)) and water (S(AQ)) were performed on a data set of 41 compounds (n = 41) comprising 39 prodrugs of 5-fluorouracil (5-FU), theophylline (Th), and 6-mercaptopurine (6-MP), in addition to 5-FU and Th, using four models. Two series/parallel models have been developed that allow an aqueous-only path in parallel with a lipid-only path and with a lipid-aqueous series path for the permeation of solutes through skin: log J(M) = log ¿1/[1/(aS(LIPID) 10(PhiMW)) + 1/(bS(AQ)/MW(1/2))] + cS(LIPID)10(PhiMW) + dS(AQ)/MW(1/2)¿ where a, b, c, and d are coefficients for flux through the lipid and aqueous portions of the series path, the lipid-only path, and the aqueous-only path, respectively, and Phi is the dependence of diffusivity in lipid on MW. In the first series/parallel model, S(LIPID) was predicted by S(IPM), and in the second, solvatochromic series/parallel model, S(LIPID) was predicted by S(IPM)(k MW + Omegai) where Omega(i) is the sum of the solvatochromic terms alpha, beta, pi, and R(2), and k is the coefficient for the dependence of partitioning on MW. Using the n = 41 solutions, the coefficients for the aqueous-only path were very small or not different from zero in the two series/parallel models, so only two-path series/parallel models were compared with the solvatochromic and transformed Potts-Guy models where a homogeneous barrier to permeation was assumed. For each model, one compound at a time was omitted from the data set and new parameter estimates were obtained for these 41-1 solutions and used to predict log J(M) for the omitted compound. The average errors of prediction of log J(M) (experimental log J(M) - predicted log J(M)) for the four models were 0.134 for the series/parallel (r(2) = 0.937), 0.127 for the solvatochromic series/parallel (r(2) = 0.967), 0.150 for the solvatochromic (r(2) = 0.950), and 0.134 log units for the transformed Potts-Guy model (r(2) = 0.944). Thus, the solvatochromic series/parallel model provides fit and predictive ability comparable to or slightly superior to previous models that assumed homogeneity of the diffusional barrier to flux in the rate-determining step, provides further theoretical support against the existence of a high capacity aqueous-only path, and provides further insight into the physicochemical properties that should be incorporated into solutes to optimize their flux. Using the solvatochromic series/parallel model, the parameter estimates for the n = 41 solution were used to calculate the flux of each compound through the two paths. For compounds with log partition coefficients (K(IPM:AQ)) of <0.8, permeation was mostly by the lipid-aqueous series path; for compounds with log K(IPM:AQ) >1.0, permeation was mostly by the lipid-only path; the lipid-aqueous series path exhibited the higher carrying capacity. (c) 2000 Wiley-Liss, Inc.