Original Research, Animal Studies, Pharmacology/Drug Development, Method

The oral delivery of diclofenac sodium (DNa), a non-steroidal analgesic, anti-inflammatory drug, is associated with various gastrointestinal side effects. The aim of the research was to appraise the potential of transdermal delivery of DNa using bilosomes as a vesicular carrier (BSVC) in inflamed paw edema. DNa-BSVCs were elaborated using a thin-film hydration technique and optimized using a 3.2 multilevel categoric design with Design Expert software 10 software (Stat-Ease, Inc., Minneapolis, MI, USA). The effect of formulation variables on the physicochemical properties of BSVC, as well as the optimal formulation selection, was investigated. The BSVCs were evaluated for various parameters including entrapment efficiency (EE%), vesicle size (VS), zeta potential (ZP) and permeation studies. The optimized BSVC was characterized for in vitro release, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and incorporated into hydrogel base. The optimized DNa-BSVC gel effectiveness was assessed in vivo using carrageenan-induced paw edema animal model via cyclooxygenase 2 (COX-2), interleukin 6 (IL-6), Hemooxygenase 1 (HO-1) and nuclear factor-erythroid factor2-related factor 2 (Nfr-2) that potentiate anti-inflammatory and anti-oxidant activity coupled with histopathological investigation. The resulting vesicles presented VS from 120.4 ± 0.65 to 780.4 ± 0.99 nm, EE% from 61.7 ± 3.44 to 93.2 ± 2.21%, ZP from -23.8 ± 2.65 to -82.1 ± 12.63 mV and permeation from 582.9 ± 32.14 to 1350.2 ± 45.41 µg/cm. The optimized BSVCs were nano-scaled spherical vesicles with non-overlapped bands of their constituents in the FTIR. Optimized formulation has superior skin permeability ex vivo approximately 2.5 times greater than DNa solution. Furthermore, histological investigation discovered that the formed BSVC had no skin irritating properties. It was found that DNa-BSVC gel suppressed changes in oxidative inflammatory mediators (COX-2), IL-6 and consequently enhanced Nrf2 and HO-1 levels. Moreover, reduction of percent of paw edema by about three-folds confirmed histopathological alterations. The results revealed that the optimized DNa-BSVC could be a promising transdermal drug delivery system to boost anti-inflammatory efficacy of DNa by enhancing the skin permeation of DNa and suppressing the inflammation of rat paw edema.

Neuropathic pain affects 7-10% of the adult population. Being able to accurately monitor biological changes underlying neuropathic pain will improve our understanding of neuropathic pain mechanisms and facilitate the development of novel therapeutics. Positron emission tomography (PET) is a noninvasive molecular imaging technique that can provide quantitative information of biochemical changes at the whole-body level by using radiolabeled ligands. One important biological change underlying the development of neuropathic pain is the overexpression of α2δ-1 subunit of voltage-dependent calcium channels (the target of gabapentin). Thus, we hypothesized that a radiolabeled form of gabapentin may allow imaging changes in α2δ-1 for monitoring the underlying pathophysiology of neuropathic pain. Here, we report the development of two F-labeled derivatives of gabapentin (trans-4-[F]fluorogabapentin and cis-4-[F]fluorogabapentin) and their evaluation in healthy rats and a rat model of neuropathic pain (spinal nerve ligation model). Both isomers were found to selectively bind to the α2δ-1 receptor with trans-4-[F]fluorogabapentin having higher affinity. Both tracers displayed around 1.5- to 2-fold increased uptake in injured nerves over the contralateral uninjured nerves when measured by gamma counting ex vivo. Although the small size of the nerves and the signal from surrounding muscle prevented visualizing these changes using PET, this work demonstrates that fluorinated derivatives of gabapentin retain binding to α2δ-1 and that their radiolabeled forms can be used to detect pathological changes in vitro and ex vivo. Furthermore, this work confirms that α2δ-1 is a promising target for imaging specific features of neuropathic pain.

The burst release of small molecular water-soluble drugs is a major problem when pursuing their long-acting formulations. Although various types of carrier materials have been developed for tackling this problem, it is still a big challenge to prevent water-soluble small molecules from fast release and diffusion. In this study, a biomineralization strategy based upon a self-assembling peptide is proposed for the slow release of lidocaine, a classic anesthetic with high solubility and a very small molecular weight. A bolaamphiphilic peptide was designed to self-assemble and produce negatively charged nanofibers, which were used as the template to absorb positively charged lidocaine molecules through an electrostatic interaction. The biomineralization of lidocaine was then induced by adjusting the pH, which lead to the formation of lidocaine microcrystals with a homogenous size. The microcrystals were incorporated into a hyaluronic acid hydrogel to form an injectable formulation. This formulation slowly released lidocaine and generate a prolonged anesthetic and analgesic effect in rodent models. Due to the constrained local and plasma lidocaine concentration, as well as the biocompatibility and biodegradability of the peptide materials, this formulation also showed considerable safety. These results suggest that nanofiber assisted biomineralization can provide a potential strategy for the fabrication of long-acting formulations for small molecular water-soluble drugs. STATEMENT OF SIGNIFICANCE: Long-acting formulations are highly pursued to achieve stronger therapeutic effect, or to avoid repeated administration of drugs, especially through painful injection. Using carrier materials to slow down the release of bioactive molecules is a common strategy to reach this goal. However, for many water-soluble small molecular drugs currently used in clinic, it is notoriously difficult to slow down their release and diffusion. This study proposes a novel strategy based on a controllable mineralization process using self-assembling peptide nanofibers as the template. Taking lidocaine as an example, we showed how peptide-drug microcrystals with well-controlled size and shape could be obtained, which exhibit significantly prolonged anesthetic and analgesic effect. As a proof-of-concept study, this work proposes a promising strategy to control the release of water-soluble small molecular drugs.

An animal model of voluntary oral morphine consumption would allow for a pre-clinical evaluation of new treatments aimed at reducing opioid intake in humans. However, the main limitation of oral morphine consumption in rodents is its bitter taste, which is strongly aversive. Taste aversion is often overcome by the use of adulterants, such as sweeteners, to conceal morphine taste or bitterants in the alternative bottle to equalize aversion. However, the adulterants' presence is the cause for consumption choice and, upon removal, the preference for morphine is not preserved. Thus, current animal models are not suitable to study treatments aimed at reducing consumption elicited by morphine itself. Since taste preference is a learned behavior, just-weaned rats were trained to accept a bitter taste, adding the bitterant quinine to their drinking water for one week. The latter was followed by allowing the choice of quinine or morphine (0.15 mg/mL) solutions for two weeks. Then, quinine was removed, and the preference for morphine against water was evaluated. Using this paradigm, we show that rats highly preferred the consumption of morphine over water, reaching a voluntary morphine intake of 15 mg/kg/day. Morphine consumption led to significant analgesia and hyperlocomotion, and to a marked deprivation syndrome following the administration of the opioid antagonist naloxone. Voluntary morphine consumption was also shown to generate brain oxidative stress and neuroinflammation, signs associated with opioid dependence development. We present a robust two-bottle choice animal model of oral morphine self-administration for the evaluation of therapeutic interventions for the treatment of morphine dependence.

Pharmacology and optogenetics are widely used in neuroscience research to study the central and peripheral nervous systems. While both approaches allow for sophisticated studies of neural circuitry, continued advances are, in part, hampered by technology limitations associated with requirements for physical tethers that connect external equipment to rigid probes inserted into delicate regions of the brain. The results can lead to tissue damage and alterations in behavioral tasks and natural movements, with additional difficulties in use for studies that involve social interactions and/or motions in complex 3-dimensional environments. These disadvantages are particularly pronounced in research that demands combined optogenetic and pharmacological functions in a single experiment. Here, we present a lightweight, wireless, battery-free injectable microsystem that combines soft microfluidic and microscale inorganic light-emitting diode probes for programmable pharmacology and optogenetics, designed to offer the features of drug refillability and adjustable flow rates, together with programmable control over the temporal profiles. The technology has potential for large-scale manufacturing and broad distribution to the neuroscience community, with capabilities in targeting specific neuronal populations in freely moving animals. In addition, the same platform can easily be adapted for a wide range of other types of passive or active electronic functions, including electrical stimulation.