Liposomal butamben gel formulations: toxicity assays and topical anesthesia in an animal model

When it is too much: Identifying butamben excess on the surface of pharmaceutical preformulation samples by Raman mapping

Butamben is a topical local anesthetic which formulation in lipid-based drug delivery systems (DDS) is challenging due to its affinity for hydrophilic excipients. This means that a medium polarity excipient is preferred for the development of a stable nanostructured lipid carrier (NLC) formulation. In turn, in NLC, the type and number of excipients will determine the active pharmaceutical ingredient (API) solubility and the maximum drug upload. To solve this dilemma and get the best formulation, a throughout screening study to evaluate API solubilization in different excipients was carried out. Subsequently, excipients with different solubilization capacities were selected for microscopic evaluation by Raman mapping, and in turn analysis of the distributional homogeneity index (DHI) and standard deviation of the histograms allowed solving the posed question. Design of experiments (DoE) was employed to understand better the interactions between the excipients; linear and higher-order models were obtained with R2 above of 0.8824. Even though DHI is a good parameter to be used as response, an API concentration higher than 30% (w/w) provided a homogeneous surface in case of good miscibility and, in this case, this parameter needs to be employed with an inspection and/or evaluation of other parameters. A curve of concentration vs. mean scores of images proved to be an alternative to identify the saturation/limit of linear range.

Neither too little nor too much: Finding the ideal proportion of excipients using confocal Raman and chemometrics

The applications of Raman imaging in pharmaceutical field are ever-increasing due its ability to obtain spatial and spectral information simultaneously, once it allows determine the chemical distribution of compounds. In this sense, it is used to study homogeneity, of paramount importance during the development of pharmaceutical formulations due to its relation to stability, safety and efficacy. Commonly, just surface is analyzed, but confocal Raman spectroscopy can also characterize the inner part of samples, allowing to determine phase separation in the early stages. In this sense, confocal 3D Raman microscopy was crucial to obtain the optimal proportion of Apifil®, Capryol® 90 and Transcutol® to promote controlled release of the local anesthetic butamben (BTB). 3D chemical maps were obtained by classical least squares (CLS) using pure compound spectra as S matrix, showing that chemical distribution throughout the material was different. Knowing that the composition of samples affects the homogeneity parameter, standard deviation and distributional homogeneity index (DHI) were used in mixture experimental design (DoE). From this analysis, it was revealed that a correct amount of Capryol® 90 enhances both miscibility and solubility. Furthermore, suitable miscibility was observed in two ratio proportions of excipients with a desirability of 0.783 and 0.742. These results unequivocally demonstrated that confocal Raman microscopy combined to DoE can bring pharmaceutical development to a higher level.

Insightful exploring of advanced nanocarriers for the topical/transdermal treatment of skin diseases

Dermatological products constitute a big segment of the pharmaceutical market. From conventional products to more advanced ones, a wide variety of dosage forms have been developed till current date. A representative of the advanced delivery means is carrier-based systems, which can load large number of drugs for treatment of dermatological diseases, or simply for cosmeceutical purposes. To make them more favorable for topical delivery, further incorporation of these carriers in a topical vehicle, such as gels or creams is made. Therefore in this review article, an overview is compiled of the most commonly encountered novel carrier based topical delivery systems; namely lipid based (nanoemulsions, microemulsions, solid lipid nanoparticles [SLNs] and nanostructured lipid carriers [NLCs]), and vesicular carriers (non-deformable, such as liposomes, niosomes, emulsomes and cerosomes, and deformable, such as transfersomes, ethosomes, transethosomes, and penetration enhancer vesicles), with special emphasis on those loaded in a secondary gel vehicle. A special focus was made on the commonly encountered dermatological diseases, such as bacterial and fungal infections, psoriasis, dermatitis, eczema, vitiligo, oxidative damage, aging, alopecia, and skin cancer.

Recent advances in the development of nanomedicines for the treatment of ischemic stroke

Ischemic stroke is still a serious threat to human life and health, but there are few therapeutic options available to treat stroke because of limited blood-brain penetration. The development of nanotechnology may overcome some of the problems related to traditional drug development. In this review, we focus on the potential applications of nanotechnology in stroke. First, we will discuss the main molecular pathological mechanisms of ischemic stroke to develop a targeted strategy. Second, considering the important role of the blood-brain barrier in stroke treatment, we also delve mechanisms by which the blood-brain barrier protects the brain, and the reasons why the therapeutics must pass through the blood-brain barrier to achieve efficacy. Lastly, we provide a comprehensive review related to the application of nanomaterials to treat stroke, including liposomes, polymers, metal nanoparticles, carbon nanotubes, graphene, black phosphorus, hydrogels and dendrimers. To conclude, we will summarize the challenges and future prospects of nanomedicine-based stroke treatments.

Prolonged anesthesia and decreased toxicity of enantiomeric-excess bupivacaine loaded in ionic gradient liposomes

Bupivacaine is the most employed local anesthetic in surgical procedures, worldwide. Its systemic toxicity has directed the synthesis of the less toxic, S(-) enantiomer. This work describes a formulation of ionic gradient liposomes (IGL) containing _S75BVC, an enantiomeric excess mixture of 75% S(-) and 25% R(+) bupivacaine. IGL prepared with 250 mM (NH₄)₂SO₄ in the inner aqueous core of phosphatidylcholine and cholesterol (3:2 mol%) vesicles plus 0.5% _S75BVC showed average sizes of 312.5 ± 4.5 nm, low polydispersity (PDI < 0.18), negative zeta potentials (-14.2 ± 0.2 mV) and were stable for 360 days. The encapsulation efficiency achieved with IGL_S75BVC (%EE = 38.6%) was higher than with IGL prepared with racemic bupivacaine (IGL_RBVC, %EE = 28.3%). TEM images revealed spherical vesicles and µDSC analysis provided evidence on the interaction of the anesthetic with the lipid bilayer. Then, in vitro - release kinetics and cytotoxicity- and in vivo - toxic effects in Zebrafish and biochemical/histopathological analysis plus analgesia in Wistar rats - tests were performed. IGL_S75BVC exhibited negligible toxicity against Schwann cells and Zebrafish larvae, and it did not affect biochemical markers or the morphology of rat tissues (heart, brain, cerebellum, sciatic nerve). The in vitro release of _S75BVC from IGL was extended from 4 to 24 h, justifying the prolonged anesthetic effect measured in rats (~9 h). The advantages of IGL_S75BVC formulation over IGL_RBVC and plain bupivacaine formulations (prolonged anesthesia, preferential sensorial blockade, and no toxicity) confirm its potential for clinical use in surgical anesthesia.

Nanohybrid hydrogels designed for transbuccal anesthesia

BACKGROUND

Local anesthesia in dentistry is by far the most terrifying procedure for patients, causing treatment interruption. None of the commercially available topical formulations is effective in eliminating the pain and phobia associated to the needle insertion and injection.

MATERIALS AND METHODS

In this work we prepared a nanostructured lipid-biopolymer hydrogel for the sustained delivery of lidocaine-prilocaine (LDC-PLC) for transbuccal pre-anesthesia. The lipid was composed of optimized nanostructured lipid carriers (NLC) loaded with 5% LDC-PLC (NLC/LDC-PLC). The biopolymer counterpart was selected among alginate, xanthan (XAN), and chitosan matrices. The XAN-NLC hydrogel presented the most uniform aspect and pseudoplastic rheological profile, as required for topical use; therefore, it was selected for subsequent analyses. Accelerated stability tests under critical conditions (40°C; 75% relative humidity) were conducted for 6 months, in terms of drug content (mg/g), weight loss (%), and pH.

RESULTS

In vitro LDC-PLC release profile through Franz diffusion cells revealed a bimodal kinetics with a burst effect followed by the sustained release of both anesthetics, for 24 hours. Structural analyses (fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy) gave details on the molecular organization of the hybrid hydrogel, confirming the synergic interaction between the components. Safety and efficacy were evaluated through in vitro cell viability (3T3, HaCat, and VERO cells) and in vivo antinociceptive (tail-flick, in mice) tests, respectively. In comparison to a control hydrogel and the eutectic mixture of 5% LDC-PLC cream (EMLA®), the XAN-NLC/LDC-PLC hybrid hydrogel doubled and quadrupled the anesthetic effect (8 hours), respectively.

CONCLUSION

Considering such exciting results, this multifaceted nanohybrid system is now ready to be further tested in clinical trials.

Current progress and challenges of nanoparticle-based therapeutics in pain management

Pain is a widespread and growing health problem worldwide that exerts a considerable social and economic impact on both patients and healthcare systems and, therefore, on society in general. Although current treatment modalities include a wide variety of pharmacological and non-pharmacological approaches, due to the complexity of pain and individual differences in clinical response these options are not always effective in mitigating and relieving pain. In addition, some pain drugs such as non-steroidal anti-inflammatory drugs (NSAIDs), local anesthetics and opioids show several unfavorable side effects. Therefore, current research advances in this medical field are based on the development of potential treatments to address many of the unmet needs and to overcome the existing limitations in pain management. Nanoparticle drug delivery systems present an exciting opportunity as alternative platforms to improve efficacy and safety of medications currently in use. Herein, we review a broad range of nanoparticle formulations (organic nanostructures and inorganic nanoparticles), which have been developed to encapsulate an array of painkillers, paying special attention to the key advantages that these systems offer, (compared to the use of the free drug), as well as to the more relevant results of preclinical studies in animal models. Additionally, we will briefly discuss the impact of some of these nanoformulations in clinical trials.