Development of Chlorhexidine Digluconate and Lippia sidoides Essential Oil Loaded in Microemulsion for Disinfection of Dental Root Canals: Substantivity Profile and Antimicrobial Activity

The dental intracanal disinfection is crucial to achieve the success of endodontic treatment, avoiding the maintenance of endodontic infections. Chlorhexidine digluconate can act as an irrigating agent for it. However, it can cause tissue irritation in high concentrations. Therefore, combinations with other antimicrobial agents and more efficient therapeutic alternatives are studied, which make it possible to administer drugs more safely and with minimal adverse effects. Thus, the objective of this study was the development of a microemulsion containing chlorhexidine digluconate and essential oil of Lippia sidoides to be used for disinfection of dental root canals and to evaluate its profile of substantivity and antimicrobial activity. The microemulsions were obtained through phase diagrams, using the spontaneous formation method. We completed a physical-chemical characterization and evaluate the stability of the microemulsions, in addition to the substantivity profile in a bovine root dentin model, and in vitro antibacterial effect on Enterococcus faecalis. A method for quantifying chlorhexidine was developed using UV-Vis spectroscopy. The microemulsions showed acid pH, conductivity above 1.3 μScm^-1, and dispersion index similar to water. The microemulsions showed antimicrobial inhibition halos similar to the commercial gel conventionally used, but with four times more substantivity to dentinal tissues. Microemulsions were obtained as a therapeutic alternative to formulations available on the market, presenting themselves as a system with great potential for the administration of drugs for disinfection of root canals.

Mucoadhesive emulgel systems containing curcumin for oral squamous cell carcinoma treatment: From pre-formulation to cytotoxicity in tissue-engineering oral mucosa

Current oral squamous cell carcinoma chemotherapies demonstrate off-target toxicity, which could be reduced by local delivery. Curcumin acts via many cellular targets to give anti-cancer properties; however the bioavailability is hindered by its physicochemical characteristics. The incorporation of curcumin into emulgel systems could be a promising approach for its solubilization and delivery. The aim of this work was to develop emulgel systems containing curcumin for the treatment of oral cancer. The emulgels containing curcumin were prepared with poloxamer 407, acrylic acid derivatives, oil phase (sesame oil or isopropyl myristate). The more stable system was evaluated for mechanical and rheological properties, as well as, the in vitro drug release profile, permeation and cytotoxic potential to oral mucosa models. The flow-throw system evidenced that the formulations could keep 5 min over porcine oral mucosa. Emulgel showed pseudoplastic behavior and a gelation temperature of 33 °C, which ensure their higher consistency. In addition, 70% of the incorporated curcumin was released within 24 h in an in vitro drug release study and could permeate porcine oral mucosa. Monolayers cultures and tissue-engineered models showed the selectivity of the drug and systems for tumor cells. The physicochemical properties, subsequent release and permeation of curcumin to selectivity kill cancer cells could be improved by the incorporation into emulgel systems.

Amphiphile behavior in mixed solvent media I: self-aggregation and ion association of sodium dodecylsulfate in 1,4-dioxane-water and methanol-water media

Mixed aquo-organic solvents are used in chemical, industrial, and pharmaceutical processes along with amphiphilic materials. Their fundamental studies with reference to bulk and interfacial phenomena are thus considered to be important, but such detailed studies are limited. In this work, the interfacial adsorption of sodium dodecylsulfate (SDS, C12H25SO4(-)Na(+)) in dioxane-water (Dn-W) and methanol-water (Ml-W) media in extensive mixing ratios along with its bulk behavior have been investigated. The solvent-composition-dependent properties have been identified, and their quantifications have been attempted. The SDS micellization has been assessed in terms of different solvent parameters, and the possible formation of an ion pair and triple ion of the colloidal electrolyte, C12H25SO4(-)Na(+) in the Dn-W medium has been correlated and quantified. In the Ml-W medium at a high volume percent of Ml, the SDS amphiphile formed special associated species instead of ion association. The formation of self-assembly and the energetics of SDS in the mixed solvent media have been determined and assessed using conductometry, calorimetry, tensiometry, viscometry, NMR, and DLS methods. The detailed study undertaken herein with respect to the behavior of SDS in the mixed aquo-organic solvent media (Dn-W and Ml-W) is a new kind of endeavor.

Behavior of the amphiphile CHAPS alone and in combination with the biopolymer inulin in water and isopropanol-water media

Self-aggregation of the zwitterionic surfactant 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) in water and isopropanol-water media, and interaction of the amphiphile with the biopolymer inulin in these media were investigated. The micellar properties of the zwitterionic surfactant and its associated interfacial and bulk properties along with the related energetic, and aggregation number were determined. The different stages of interaction of the CHAPS-inulin combines were identified and assessed. The complexes were formed and aggregated in solution at different stages of their molecular compositions. The aggregated sizes were determined by dynamic light scattering study and the morphology in the solvent removed states were examined using scanning electron microscope and transmission electron microscope techniques. The results witnessed formation of ensembles of varied and striking patterns.

Physicochemistry of interaction between the cationic polymer poly(diallyldimethylammonium chloride) and the anionic surfactants sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium N-dodecanoylsarcosinate in water and isopropyl alcohol-water media

The physicochemistry of interaction of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) with the anionic surfactants sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium N-dodecanoylsarcosinate was studied in detail using tensiometry, turbidimetry, calorimetry, viscometry, dynamic light scattering (DLS), and scanning electron microscopy (SEM). Fair interaction initially formed induced small micelles of the surfactants and later on produced free normal micelles in solution. The interaction process yielded coacervates that initially grew by aggregation in the aqueous medium and disintegrated into smaller species at higher surfactant concentration. The phenomena observed were affected by the presence of isopropyl alcohol (IP) in the medium. The hydrodynamic sizes of the dispersed polymer and its surfactant-interacted species were determined by DLS measurements. The surface morphologies of the solvent-removed PDADMAC and its surfactant-interacted complexes from water and IP-water media were examined by the SEM technique. The morphologies witnessed different patterns depending on the composition and the solvent environment. The head groups of the dodecyl chain containing surfactants made differences in the interaction process.

Critical evaluation of the therapeutic potential of bassic acid incorporated in oil-in-water microemulsions and poly-d,l-lactide nanoparticles against experimental leishmaniasis

Bassic acid, an unsaturated triterpene acid isolated from Mimusops elangii, was tested for its antileishmanial properties both in vitro and in vivo. The in vitro antileishmanial activity of bassic acid being encouraging, its activity in vivo was evaluated in hamster models of visceral leishmaniasis, both in free form, as well as incorporated in two different delivery systems, viz microemulsions and polylactide nanoparticles. The delivery systems were prepared by published protocols. The percentage intercalation of bassic acid in nanoparticles and microemulsion was found to be about 50 and 100, respectively, when determined at its absorption maxima (lambda(max)) 285 nm (epsilon(m) = 2.3 x 10(2) M(-1) cm(-1)). At an equivalent dose of 2 mg kg(-1) body weight, when injected subcutaneously for a total of six doses in 15 days, bassic acid was found to reduce spleen parasite loads by 45, 62 and 78% in free, microemulsion-incorporated and nanoparticle-incorporated forms, respectively. A comparison of specific biochemical tests related to normal liver and kidney functions revealed that the nanoparticulate form was successful in significantly reducing the hepatotoxicity and nephrotoxicity of the free drug, but the microemulsion delivery system was less effective and toxic to liver and kidney to some extent. Confocal microscopic images of Leishmania donovani promastigotes treated with bassic acid revealed that the drug induced necrotic cell death due to non-specific membrane damage. Because of its high efficacy as well as non-hepatotoxicity and non-nephrotoxicity, the nanoparticulate form of bassic acid may be considered for clinical application in humans rather than the microemulsion incorporated form.

Designing and Testing of an Effective Oil-in-Water Microemulsion Drug Delivery System forIn VivoApplication

The phase behavior of a new psedoternary system of clove oil/Tween 20 has been studied. Several compositions from the single-phase region were selected and their stability toward time, temperature, and electrolytes has been examined. A particular composition(clove oil/Tween 20/water as 5/30/65) was chosen as the drug delivery system from the clear oil-in-water zone of the pseudoternary system. The droplet dimension and the polydispersity state of the particular composition was determined by dynamic light scattering. A bioactive compound quarcetin was encapsulated in the vehicle. The efficacy of the drug in the vehicle was examined against leishmaniasis in hamster models. The hepatotoxicity of the vehicle (o/w microemulsion) with and without the drug quarcetin was examined by estimating serum alkaline phosphatase, glutamate pyruvate transaminase, urea, and creatinine.

New Pharmaceutical Microemulsion System for Encapsulation and Delivery of Diospyrin, a Plant-Derived Bioactive Quinonoid Compound

A new vegetable oil based oil-in-water microemulsion is developed and characterized as a prospective delivery system for in vivo application A particular weight percent composition 5/30/65 (clove oil/Tween-20/water) was selected (V1) from the clear oil-in-water zone of the pseudoternary phase diagram comprising clove oil, polyoxyethylene sorbitan monolaurate (Tween-20), and water. Two modifications of V1, (V2 and V3) were prepared by addition of dipalmitoyl phosphatidyl choline (DPPC), and a mixture of DPPC and cholesterol, respectively. A model drug diospyrin (a plantderived quinonoid compound) was encapsulated in the dispersed clove oil droplets of the three systems and designated as DV1, DV2, and DV3, respectively. The size of the dispersed clove oil droplets ranged between 9-20 nm as determined by dynamic light scattering. The stability of the vehicles, before and after encapsulation, was assessed under varying conditions of time and temperature and was found to be stable for 1 year and over a temperature range of 4-40 degrees C. The ultraviolet-visible spectrum of diospyrin after encapsulation in the compartmentalized medium remained almost identical to that dissolved in chloroform. The single-dose acute toxicity of V1 and DV1 was assessed in vivo by carrying out survival study and enzyme assay in Swiss Albino mice. The vehicle was safe at a volume of 0.05 ml when injected intraperitoneally into the mice.

Biocompatible microemulsions and their prospective uses in drug delivery

Efficacy of lipophilic drugs is often hindered due to their poor aqueous solubility leading to low absorption after in vivo administration. A part of the administered dose is absorbed and reaches the pharmacological site of action and the remainder causes toxicity and undesirable side effects due to unwanted biodistribution. Enhancement in drug efficacy and lowering of drug toxicity could be achieved through encapsulation and delivery of the lipophilic drugs in aqueous based delivery systems. Microemulsions are macroscopically homogeneous pseudoternary and ternary colloidal assemblies having polar and nonpolar micro domains. Their dispersed phases in nanodimension have good shelf-life (due to thermodynamic stability), large surface area, low viscosity (in some compositions), and ultraslow surface tension. These properties qualify them to be prospective drug delivery systems provided they are composed of biocompatible excipients. Due to the existence of polar, nonpolar, and interfacial microdomains, encapsulation of different kinds of drugs is possible. The review entails reports on development and characterization of biocompatible microemulsion systems and their evaluation as probable vehicles for encapsulation, stabilization, and delivery of bioactive natural products and prescription drugs.

Interfacial and bulk behavior of sodium dodecyl sulfate in isopropanol-water and in isopropanol-poly(vinylpyrrolidone)-water media

The surface activity of isopropanol (IP) and poly(vinylpyrrolidone) (PVP) at the air/water interface has been studied. The self-aggregation of sodium dodecyl sulfate (SDS) in IP-water as well as in IP-PVP-water media has been investigated using physical methods, viz., tensiometry, conductometry, calorimetry, and viscometry. The interaction of SDS with PVP in IP-water medium as well as its self-aggregation (or micellization) in the presence of PVP has been assessed. The results reveal a fair degree of surface activity of IP in aqueous medium, which is only moderate for PVP. The critical micellar concentration (CMC) of SDS passes through a minimum at (v/v) % IP = 6.62. SDS interacts with PVP, yielding a critical aggregation concentration (CAC) at a low [SDS], independent of IP content in the medium. At a higher [SDS], free micelle formation takes place in solution, which is lower in mixed solvent than in water and is independent of solvent composition by tensiometry, but not by conductometry and calorimetry. The viscosity of micelle-interacted PVP in solution takes a long time to stabilize, whereas, for non-interacting additives, such as NaCl and cetyltrimethylammonium bromide (CTAB), it is time independent.

Enhanced in vitro percutaneous absorption and in vivo anti-inflammatory effect of a selective cyclooxygenase inhibitor using microemulsion

Celecoxib, a specific COX-2 inhibitor, was recently approved for the treatment of rheumatoid and osteoarthritis, acute pain, familial adenomatous polyposis and primary dysmenorrhea. Oral administration of celecoxib is effective against ultraviolet B radiation (UVB)-induced skin carcinogenesis; however, its clinical use is restricted because of its failure to block the characteristic cutaneous inflammatory response and lower availability at the site of inflammation. Topical application of celecoxib has been effective compared with oral in certain clinical conditions. The present study was undertaken to develop and investigate the development of microemulsion system (isopropyl myristate/medium-chain glyceride/polysorbate 80/water) for topical delivery of celecoxib. The pseudoternary phase diagram was constructed with constant surfactant concentration, and several compositions were identified and characterized by using dynamic light scattering. The in vitro permeation rate of celecoxib through rat skin was determined for microemulsions, microemulsion gel, and cream by using the modified Franz-type diffusion cell. In all formulations tested, celecoxib permeated more quickly, and the microemulsions increased the permeation rate of celecoxib up to 5 and 11 times compared with those of microemulsion gel and cream, respectively. Increasing the concentration of medium-chain mono-/di-glyceride in microemulsion imparted increased droplet size and viscosity and decreased diffusion coefficient. In vivo anti-inflammatory study suggested that the developed microemulsion formulations might serve as potential drug vehicle for the prevention of UVB-induced skin cancer.

Formulation and physicochemical characterization of microemulsion system using isopropyl myristate, medium-chain glyceride, polysorbate 80 and water

The phase behavior of the system isopropyl myristate/medium-chain glyceride/polysorbate 80/water forming both w/o and o/w microemulsions has been studied to develop microemulsion comprising of pharmaceutical excipients. The pseudo-ternary phase diagrams with large monophasic zones and gel formation were realized and several compositions were identified in the phase diagram for rheological, dynamic light scattering (DLS) and calorimetric measurements. The identified systems at different temperatures behaved as Newtonian fluid and the activation parameters for their viscous flow were evaluated. From DLS measurements, hydrodynamic diameter, polydispersity and diffusion coefficient of the microheterogeneous dispersions were determined. The free energy, enthalpy and entropy of solution of the w/o and o/w microemulsions were determined from calorimetric measurements.

Solubilization by different-sized surfactant mixtures

The solubilization phenomenon was investigated in mixed surfactant systems. The solubilization power of a mixed surfactant reaches its maximum at a particular temperature at each mixing ratio of surfactants. When the mole fraction of C4E1 in the total surfactant (w1 value) was varied in a water/C12E5/C4E1/decane system, the minimum mole fraction of total surfactant in the system necessary to obtain a single microemulsion phase (xi value) was almost unchanged for w1<0.3, whereas it increased remarkably for w1>0.8. The molar solubilization capacity (Cs=(1-xi)/xi) of the mixed surfactant decreased remarkably for w1<0.3, whereas it decreased gradually for w1>0.8. The result [Formula: see text] is due largely to the characteristic of the function xi(Cs)=1/(1+Cs), specifically, [Formula: see text] , where dxi/dw1=(dxi/dCs)(dCs/dw1). The partial molar solubilization capacity (Cs) of C4E1 was negative at almost all w1, but the Cs value of C12E5 went through a maximum on the addition of C4E1. Propanol (a cosurfactant) has the same effect on the solubilization phenomenon in the water/C12E6/propanol/heptane system. In the water/C12E5/C12E7/decane system, the Cs value of each surfactant did not vary greatly as the mixing ratio of surfactants was varied. The Cs and xi values were close to molar additivity for each mixing ratio.

Physicochemical investigations of microemulsification of eucalyptus oil and water using mixed surfactants (AOT+Brij-35) and butanol

Microemulsification of a vegetable oil (eucalyptus) with single and mixed surfactants (AOT and Brij-35), cosurfactant of different lipophilicities (isomers of butanol), and water were studied at different surfactant and cosurfactant mixing ratios. The phase diagrams of the quaternary systems were constructed using unfolded and folded tetrahedron, wherein the phase characteristics of different ternary systems can be underlined. The microemulsion zone was found to be dependent upon the mixing ratios of surfactant and cosurfactant; the largest microemulsion zone was formed with 1:1 (w/w) S:CS. The effects of temperature and additives (NaCl, urea, glucose, and bile salts of different concentrations) on the phase behavior were examined. The mixed microemulsion system showed temperature insensitivity, whereas the Brij-35 (single) stabilized system exhibited a smaller microemulsion zone at elevated temperature. NaCl and glucose increased the microemulsion zone up to a certain concentration, beyond which the microemulsion zones were decreased. These additives decreased the microemulsion zones as temperature was increased. The effect of urea on microemulsion zone was found to be insignificant even at the concentration 3.0 mol dm(-3). Little effect on microemulsion zone was shown by NaC (sodium cholate) at 0.25 and 0.5 mol dm(-3) at different temperatures. The conductance of the single (AOT) and mixed microemulsion system (AOT+Brij-35) depends upon the water content and mixing ratios of the surfactants, and a steep rise in conductance was observed at equal weight percentages of oil and water. Viscosities for both single (AOT) and mixed (AOT+Brij-35) surfactant systems passed through maxima at equal oil and water regions showing structural transition. The viscosities for microemulsion systems increased with increasing Brij-35 content in the AOT+Brij-35 blend. Conductances and viscosities of different monophasic compositions in the absence and presence of additives (NaCl and NaC) were measured at different temperatures. The activation energy of conduction (DeltaE(cond)( *)) and the activation enthalpy for viscous flow (DeltaH(vis)( *)) were evaluated. It was found that both DeltaE(cond)( *) and DeltaH(vis)( *) were a function of the nature of the dispersion medium. Considering the phase separation point of maximum solubility, the free energy of dissolution of water or oil (DeltaG(s)(0)) at the microdispersed state in amphiphile medium was estimated and found to be a function of surfactant composition.