Maria Helena Amaral

Nanotechnological carriers for cancer chemotherapy: the state of the art.

Cancer is a term used for a heterogeneous group of malignant diseases in which abnormal cells divide without control and are able to invade other tissues, resulting in metastasis. According to the last data of World Health Organization the incidence and mortality rates of cancer are high and tend to increase. Chemotherapy is usually used in cancer treatments, but due to the lack of specificity of drugs, is associated to various and damaging side effects that have a severe impact on patients quality of life. Nanotechnology is actually an important area of interest in science and technology, which has been extensively explored during the last decade, particularly in the development of carriers for cytotoxic drugs. These carriers include vesicular and particulate systems such as liposomes, niosomes, transfersomes, ethosomes, micelles, dendrimers, and polymeric, protein and lipid nanoparticles. Polymer-drug conjugates and antibody-drug conjugates have also been studied. The present review is an attempt to contemplate the studied nanocarriers in the field of anticancer drugs delivery, their advantages and disadvantages and future perspectives.

In situ gelling systems: a strategy to improve the bioavailability of ophthalmic pharmaceutical formulations.

The low therapeutic efficacy exhibited by conventional ophthalmic solutions owing to precorneal elimination of the drug, drainage by gravity, nasolacrimal drainage, conjunctival absorption, and the absence of controlled release and of bioadhesive properties, can be overcome by the use of in situ gelling systems. The combination in the same formulation of different in situ gelling polymers with different stimuli-responsiveness mechanisms exploiting the unique physicochemical characteristics of the ocular tissues is one such strategy that has produced improved results compared with conventional systems. As we discuss here, the recent use of biodegradable and biocompatible polymers in colloidal carrier systems has proved to be the most effective strategy, resulting in the exponential increase of the bioavailability of the ophthalmic drugs.

Performance of an in vitro mucoadhesion testing method for vaginal semisolids: influence of different testing conditions and instrumental parameters.

The purpose of this work was to develop an in vitro mucoadhesion testing method for vaginal semisolid formulations. The proposed method was based on the measurement of the force (detachment force, Fdt) and the work (work of adhesion, Wad) needed to detach a sample of cow vaginal mucosa from a semisolid formulation, using a commercially available texture analyzer. Several testing conditions and instrumental parameters were tested in order to evaluate the mucoadhesive potential of a model vaginal semisolid formulation (1% Carbopol 974P gel). Also, mucoadhesive potential of several commercially available vaginal semisolid products was evaluated. Obtained results showed that the method is reproducible even when the same cow mucosa sample is used up to six times. The similarity of the fluid used to bathe the vaginal mucosa to the one naturally occurring in the vagina influenced considerably the performance of the test, advising that simulation of vaginal fluid properties is important when measuring mucoadhesive properties. Also, temperature of experiment was an important fact to be considered, as results showed slight but significant differences between body (37 degrees C) and room (20 degrees C) temperature. Fdt and Wad increased with increasing instrumental parameters while a plateau region was observable at higher values of probe speed, probe force, and mucosa/sample contact time. Comparison between results for Fdt and Wad demonstrated that although both parameters are generally in agreement, Wad seems to be more reliable and reproducible when evaluating mucoadhesion. Evaluation of commercially available formulations confirmed that experimental conditions are important features that can influence significantly the determination of mucoadhesive potential, being the proposed method an interesting and useful tool in the in vitro evaluation of vaginal semisolids.

Rheological properties of vaginal hydrophilic polymer gels.

The objective of this work was to investigate the main theological features of vaginal hydrophilic polymer gels and to elucidate about the relationship between these characteristics and gels composition, and their general influence in therapeutic/usage purpose. Flow and dynamic oscillatory properties of four commercially available (Conceptrol, Gynol II, RepHresh, and Replens) and two investigational vaginal gels were determined by cone-and-plate rheometry, at body temperature. Several parameters (apparent viscosity, complex viscosity, storage modulus, loss modulus, critical oscillatory stress, tan delta, thixotropy and yield stress) were measured and/or calculated. Gels presented non-Newtonian, pseudoplastic, thixotropic behavior, with yield stress. Overall viscosities varied between 13500 Pa.s and approximately 80 Pa.s within a biologically relevant shear rate interval (0.01-100 s(-1)). Yield stress values were variable between different determination methods but coherent in terms of ranking. Also, tested gels showed viscoelastic properties, being characterized by predominant elastic solid-like behavior. Rheological behavior of vaginal gels strongly depended on the type of gelling agent used, which potentially influences their spreading and retention properties when administered in the vaginal canal. Small variations in gels composition can result in substantial changes in their features, namely viscosity, yield stress and thixotropy. Rheological properties of tested gels appeared to be correlated with their therapeutic/usage purpose.

Solid lipid nanoparticles (SLN) - based hydrogels as potential carriers for oral transmucosal delivery of Risperidone: Preparation and characterization studies

Two different solid lipid nanoparticles (SLN)-based hydrogels (HGs) formulations were developed as potential mucoadhesive systems for risperidone (RISP) oral transmucosal delivery. The suitability of the prepared semi-solid formulations for application on oral mucosa was assessed by means of rheological and textural analysis, during 30 days. Plastic flows with thixotropy and high adhesiveness were obtained for all the tested systems, which predict their success for the oral transmucosal application proposed. The SLN remained within the colloidal range after HGs preparation. However, after 30 days of storage, a particle size increase was detected in one type of the HGs formulations. In vitro drug release studies revealed a more pronounced RISP release after SLN hydrogel entrapment, when compared to the dispersions alone. In addition, a pH-dependent release was observed as well. The predicted in vivo RISP release mechanism was Fickian diffusion alone or combined with erosion.

Local treatment of vulvovaginal candidosis : general and practical considerations.

Vulvovaginal candidosis is a common worldwide female medical problem, occurring mostly in women of childbearing age. Currently available options for the treatment of this condition include local and oral (systemic) therapy. Both alternatives have been considered equally effective in the treatment of uncomplicated vulvovaginal candidosis, although oral regimens are often preferred by physicians and women. However, local treatment presents several advantageous and unique features that may favour this therapeutic approach. The availability of numerous antifungal drugs and products for topical administration makes the selection quite challenging as this task is mostly based on personal experience or anecdotal data. Also, recent advances have been made in topical antifungal formulations and there is an increasing availability of over-the-counter products. Therefore, a review of both general and practical considerations related to the local treatment of vulvovaginal candidosis is timely.In summary, azoles and short-term regimens are usually recommended for the local treatment of vulvovaginal candidosis, with nystatin and boric acid considered as second-line alternatives. Unconventional approaches may also be regarded as suitable in patients refractory to usual treatments. In addition to the susceptibility of implicated Candida spp. to the antifungal agents, this choice should take into consideration other important issues such as particular situations (e.g. pregnancy, menopause, drug hypersensitivity), women’s preferences, and the availability, particularities and cost of antifungal formulations.

Photodegradation of avobenzone: Stabilization effect of antioxidants

Avobenzone is one of the most common UVA-filters in sunscreens, and is known to be photounstable. Some of the strategies used to stabilize this filter present some drawbacks like photosensitization reactions. Antioxidants are widely used as cosmetic ingredients that prevent photoageing and complement the photoprotection offered by the UV-filters preventing or reducing photogenerated reactive species. The purpose of this work was to study the effect of antioxidants in the photostabilization of avobenzone. The filter dissolved in dimethyl sulfoxide or incorporated in a sunscreen formulation was irradiated with simulated solar radiation (750 W/m(2)). The tested antioxidants were vitamin C, vitamin E, and ubiquinone. The area under the curve of the absorption spectrum for UVA range and the sun protection factor (SPF) were calculated. Vitamin E (1:2), vitamin C (1:0.5) and ubiquinone (1:0.5) were the more effective concentrations increasing the photostability of avobenzone. In sunscreen formulations, the most effective photostabilizer was ubiquinone which also promoted an increase in SPF. This knowledge is important to improve effectiveness of sunscreen formulation. Antioxidants can be valuable ingredients for sunscreens with a triple activity of filter stabilization, SPF boosting and photoageing prevention.

Applications of poloxamers in ophthalmic pharmaceutical formulations: an overview

Introduction: An ideal ophthalmic formulation is one that not only prolongs the contact time of the vehicle on the ocular surface but also slows down the drug elimination. The poor bioavailability and therapeutic response exhibited by the conventional ophthalmic solutions due to pre-corneal elimination of the drug may be overcome by the use of in situ gel forming systems. In situ gelling systems increase the viscosity by changing the pH or temperature in the pre-corneal region and lead to an increase of drug bioavailability by slowing drainage. Poloxamers are polyols with thermal gelling properties which are frequently included in ophthalmic formulations to improve the ocular bioavailability of drugs by increasing vehicle viscosity. Areas covered: An overview on the unique physiological characteristics of ocular globe and the limitations and disadvantages of the conventional ophthalmic pharmaceutical formulations. Readers will appreciate the different strategies to improve the absorption of drugs in the ocular globe, especially the incorporation of poloxamers in ophthalmic formulations, understanding the main advantages of the poloxamers and also learning about the different examples of applications of these polymers in ophthalmic pharmaceutical formulations. Expert opinion: Poloxamers offers a new strategy to improve bioavailability and decrease the side effects induced by the systemic absorption of topically applied ophthalmic drugs.

Degradation of UV filters 2-ethylhexyl-4-methoxycinnamate and 4-tert-butyl-4′-methoxydibenzoylmethane in chlorinated water

Environmental context The increasing use of sun-creams containing UV-filtering chemicals has led to increased inputs of these compounds to the aquatic environment. Chlorinated waters can convert these chemicals into chlorinated products whose toxic effects are of primary concern. To better understand the environmental fate of sun-cream chemicals, we studied the stability of two UV-filtering compounds under varying conditions of pH, chlorine concentration, temperature, dissolved organic matter and solar irradiation. Abstract The stability of the UV filters 2-ethylhexyl-4-methoxycinnamate (EHMC) and 4-tert-butyl-4′-methoxydibenzoylmethane (BDM) in chlorinated water was studied. High-performance liquid chromatography (HPLC)-UV-diode array detection (DAD) was used to follow the reaction kinetics of both UV filters and HPLC-tandem mass spectrometry (MS/MS) was used to tentatively identify the major transformation by-products. Under the experimental conditions used in this work both UV filters reacted with chlorine following pseudo-first order kinetics: rate constant k=0.0095±0.0007min–1 and half-life t1/2=73±4min for EHMC and rate constant k=0.006±0.001min–1 and half-life t1/2=119±14min for BDM (mean±standard deviation). The chemical transformation of the UV filters in chlorinated water led to the formation of chlorinated by-products that were tentatively identified as mono- and dichloro-substituted compounds that resulted from substitution of the hydrogen atoms in the benzene rings by one or two chlorine atoms. Experimental Box–Behnken designs were used to assess the effect of experimental factors: pH, temperature, chlorine concentration, dissolved organic matter and artificial sunlight irradiation on the transformation of the UV filters.

Applications of polymeric and lipid nanoparticles in ophthalmic pharmaceutical formulations: present and future considerations.

The unique properties and characteristics of ocular tissues and the whole set of defence mechanisms of the ocular globe make the instillation of ocular drugs into a difficult task with a low rate of therapeutic response. One of the challenges for the new generation of ophthalmic pharmaceutical formulations is to increase the bioavailability of drugs administered by the ocular route and, therefore, their therapeutic efficacy. This can be achieved with the use of some strategies that provide an increase in the formulation pre-corneal residence time, mucoadhesion and penetration across the eye tissues. Colloidal carrier systems have been very successfully used for the selective and targeted delivery of drugs for several routes of administration. In this context, nanoparticles prepared with specific polymers or lipids and coated, dispersed or suspended in polymer solutions with mucoadhesion properties or in situ gelling properties will be an excellent strategy that deserves attention and further research. In this review, the characteristics and main properties of polymeric and lipid nanoparticles are discussed and examples and advantages of the application of these colloidal carrier systems for the ophthalmic administration of drugs are presented. The future directions of the research required in this specific field are also presented.