Anti-Inflammatory and Analgesic Evaluation of a Phytochemical Intercalated into Layered Double Hydroxide.

Coumaric acid (CouH), an antioxidant molecule assimilated by food consumption, was intercalated into layered double hydroxide (LDH) nanocarrier, having zinc and aluminium ions in the layers (LDH-Cou), to evaluate its pharmacological activity through in vitro and in vivo assays in mice. Therefore, the following tests were performed: coumarate delivery in saline solution, fibroblasts' cell viability using neutral red, peritonitis induced by carrageenan, formalin test, acetic-acid-induced writhing, and tail-flick assay, for the non-intercalated CouH and the intercalated LDH-Cou system. Furthermore, different pharmacological pathways were also investigated to evaluate their possible anti-inflammatory and antinociceptive mechanisms of action, in comparison to traditionally used agents (morphine, naloxone, caffeine, and indomethacin). The LDH-Cou drug delivery system showed more pronounced anti-inflammatory effect than CouH but not more than that evoked by the classic non-steroidal anti-inflammatory drug (NSAID) indomethacin. For the analgesic effect, according to the tail-flick test, the treatment with LDH-Cou expressively increased the analgesia duration (p < 0.001) by approximately 1.7−1.8 times compared to CouH or indomethacin. Thus, the results pointed out that the LDH-Cou system induced in vivo analgesic and anti-inflammatory activities and possibly uses similar mechanisms to that observed for classic NSAIDs, such as indomethacin.

A pre-formulation study of tetracaine loaded in optimized nanostructured lipid carriers.

Tetracaine (TTC) is a local anesthetic broadly used for topical and spinal blockade, despite its systemic toxicity. Encapsulation in nanostructured lipid carriers (NLC) may prolong TTC delivery at the site of injection, reducing such toxicity. This work reports the development of NLC loading 4% TTC. Structural properties and encapsulation efficiency (%EE > 63%) guided the selection of three pre-formulations of different lipid composition, through a 23 factorial design of experiments (DOE). DLS and TEM analyses revealed average sizes (193-220 nm), polydispersity (< 0.2), zeta potential |- 21.8 to - 30.1 mV| and spherical shape of the nanoparticles, while FTIR-ATR, NTA, DSC, XRD and SANS provided details on their structure and physicochemical stability over time. Interestingly, one optimized pre-formulation (CP-TRANS/TTC) showed phase-separation after 4 months, as predicted by Raman imaging that detected lack of miscibility between its solid (cetyl palmitate) and liquid (Transcutol) lipids. SANS analyses identified lamellar arrangements inside such nanoparticles, the thickness of the lamellae been decreased by TTC. As a result of this combined approach (DOE and biophysical techniques) two optimized pre-formulations were rationally selected, both with great potential as drug delivery systems, extending the release of the anesthetic (> 48 h) and reducing TTC cytotoxicity against Balb/c 3T3 cells.

Hybrid nanofilms as topical anesthetics for pain-free procedures in dentistry.

Topical anesthetics are widely applied in order to relieve the discomfort and anxiety caused by needle insertion and other painful superficial interventions at the oral cavity. So far, there are no commercially available effective topical anesthetic formulations for that purpose, and the most of developments are related to hydrophilic and low mucoadhesive forms. Therefore, we have prepared different hybrid nanofilms composed of biopolymer matrices (chitosan, pectin, and chitosan-pectin) blended with nanostructured lipid carriers (NLC) loading the eutectic mixture of 5% lidocaine-prilocaine (LDC-PLC), in order to fulfill this gap in the market. These dual systems were processed as hybrid nanofilms by the solvent/casting method, and its mucoadhesive, structural and mechanical properties were detailed. The most appropriate hybrid nanofilm combined the advantages of both pectin (PCT) and NLC components. The resultant material presented sustained LDC-PLC release profile for more than 8 h; permeation across porcine buccal mucosa almost twice higher than control and non-cytotoxicity against 3T3 and HACAT cell lines. Then, the in vivo efficacy of PCT/NLC formulation was compared to biopolymer film and commercial drug, exhibiting the longest-lasting anesthetic effect (> 7 h), assessed by tail flick test in mice. These pectin-based hybrid nanofilms open perspectives for clinical trials and applications beyond Dentistry.

Injectable in situ forming nanogel: A hybrid Alginate-NLC formulation extends bupivacaine anesthetic effect.

Finding an ideal anesthetic agent for postoperative pain control, with long action and low side effects, is still a challenge. Local anesthetics have potential for such application if their time of action is improved. This work introduces a new hybrid formulation formed by the association of a nanostructured lipid carrier with a biopolymeric system to encapsulate bupivacaine (BVC). The hybrid formulation was physicochemical and structurally characterized by DLS, TEM, DSC, XRD and FTIR-ATR, and it remained stable for 12 months at room temperature. In vivo analgesia and imaging tests showed that the hybrid system was able to modulate the release, and to increase the concentration of BVC at the site of action, by forming a nanogel in situ. Such nanogel improved over 5 times (>24 h) the anesthesia duration, when compared to free BVC at clinical (0.5%) doses. Therefore, this novel in situ-forming nanogel shows great potential to be used in postsurgical pain control, improving the action of BVC, without losing its versatility of (infiltrative) application.

Improved efficacy of naproxen-loaded NLC for temporomandibular joint administration.

Inflammatory conditions of the temporomandibular joint (TMJ) and peripheral tissues affect many people around the world and are commonly treated with non-steroidal anti-inflammatory drugs (NSAIDs). However, in order to get desirable results, treatments with NSAIDs may take weeks, causing undesirable side effects and requiring repeated administration. In this sense, this work describes the development of an optimized nanostructured lipid carrier (NLC) formulation for intra-articular administration of naproxen (NPX). An experimental design (23) selected the best formulation in terms of its physicochemical and structural properties, elucidated by different methods (DLS, NTA, TEM, DSC, and ATR-FTIR). The chosen formulation (NLC-NPX) was tested on acute inflammatory TMJ nociception, in a rat model. The optimized excipients composition provided higher NPX encapsulation efficiency (99.8%) and the nanoparticles were found stable during 1 year of storage at 25 °C. In vivo results demonstrated that the sustained delivery of NPX directly in the TMJ significantly reduced leukocytes migration and levels of pro-inflammatory cytokines (IL-1ß and TNF-α), for more than a week. These results point out the NLC-NPX formulation as a promising candidate for the safe treatment of inflammatory pain conditions of TMJ or other joints.

Dibucaine in Ionic-Gradient Liposomes: Biophysical, Toxicological, and Activity Characterization.

Administration of local anesthetics is one of the most effective pain control techniques for postoperative analgesia. However, anesthetic agents easily diffuse into the injection site, limiting the time of anesthesia. One approach to prolong analgesia is to entrap local anesthetic agents in nanostructured carriers (e.g., liposomes). Here, we report that using an ammonium sulphate gradient was the best strategy to improve the encapsulation (62.6%) of dibucaine (DBC) into liposomes. Light scattering and nanotracking analyses were used to characterize vesicle properties, such as, size, polydispersity, zeta potentials, and number. In vitro kinetic experiments revealed the sustained release of DBC (50% in 7 h) from the liposomes. In addition, in vitro (3T3 cells in culture) and in vivo (zebrafish) toxicity assays revealed that ionic-gradient liposomes were able to reduce DBC cyto/cardiotoxicity and morphological changes in zebrafish larvae. Moreover, the anesthesia time attained after infiltrative administration in mice was longer with encapsulated DBC (27 h) than that with free DBC (11 h), at 320 µM (0.012%), confirming it as a promising long-acting liposome formulation for parenteral drug administration of DBC.

Current Challenges and Future of Lipid nanoparticles formulations for topical drug application to oral mucosa, skin, and eye.

BACKGROUND: Topical drug administration offers an attractive route with minimal invasiveness. It also avoids limitations of intravenous administration such as the first pass metabolism and presystemic elimination within the gastrointestinal tract. Furthermore, topical drug administration is safe, have few side effects, is easy to apply, and offers a fast onset of action. However, the development of effective topical formulations still represents a challenge for the desired effect to be reached, locally or systemically. Solid lipid nanoparticles and nanostructured lipid carriers are particular candidates to overcome the problem of topical drug administration. The nanometric particle size of lipid nanoparticles favors the physical adhesion to the skin or mucosal, what can also be attained with the formation of hybrid (nanoparticles/polymer) systems. METHODS: In this review, we discuss the major challenges for lipid nanoparticles formulations for topical application to oral mucosa, skin, and eye, highlighting the strategies to improve the performance of lipid nanoparticles for topical applications. Next, we critically analyzed the in vitro and in vivo approaches used to evaluate lipid nanoparticles performance and toxicity. CONCLUSION: We addressed some major drawbacks related to lipid nanoparticle topical formulations and concluded the key points that have to be overcome to help them to reach the market in topical formulations to oral mucosa, skin and eye.

Optimised NLC: a nanotechnological approach to improve the anaesthetic effect of bupivacaine.

The short time of action and systemic toxicity of local anaesthetics limit their clinical application. Bupivacaine is the most frequently used local anaesthetic in surgical procedures worldwide. The discovery that its S(-) enantiomeric form is less toxic than the R(+) form led to the introduction of products with enantiomeric excess (S75:R25 bupivacaine) in the market. Nevertheless, the time of action of bupivacaine is still short; to overcome that, bupivacaine S75:R25 (BVCS75) was encapsulated in nanostructured lipid carriers (NLC). In this work, we present the development of the formulation using chemometric tools of experimental design to study the formulation factors and Raman mapping associated with Classical Least Squares (CLS) to study the miscibility of the solid and the liquid lipids. The selected formulation of the nanostructured lipid carrier containing bupivacaine S75:R25 (NLCBVC) was observed to be stable for 12 months under room conditions regarding particle size, polydispersion, Zeta potential and encapsulation efficiency. The characterisation by DSC, XDR and TEM confirmed the encapsulation of BVCS75 in the lipid matrix, with no changes in the structure of the nanoparticles. The in vivo analgesic effect elicited by NLCBVC was twice that of free BVCS75. Besides improving the time of action, no statistical difference in the blockage of the sciatic nerve of rats was found between 0.125% NLCBVC and 0.5% free BVCS75. Therefore, the formulation allows a reduction in the required anaesthesia dose, decreasing the systemic toxicity of bupivacaine, and opening up new possibilities for different clinical applications.

Natural lipids-based NLC containing lidocaine: from pre-formulation to in vivo studies.

In a nanotechnological approach we have investigated the use of natural lipids in the preparation of nanostructured lipid carriers (NLC). Three different NLC composed of copaiba oil and beeswax, sweet almond oil and shea butter, and sesame oil and cocoa butter as structural matrices were optimized using factorial analysis; Pluronic® 68 and lidocaine (LDC) were used as the colloidal stabilizer and model encapsulated drug, respectively. The optimal formulations were characterized by different techniques (IR-ATR, DSC, and TEM), and their safety and efficacy were also tested. These nanocarriers were able to upload high amounts of the anesthetic with a sustained in vitro release profile for 24h. The physicochemical stability in terms of size (nm), PDI, zeta potential (mV), pH, nanoparticle concentration (particles/mL), and visual inspection was followed during 12months of storage at 25°C. The formulations exhibited excellent structural properties and stability. They proved to be nontoxic in vitro (cell viability tests with Balb/c 3T3 fibroblasts) and significantly improved the in vivo effects of LDC, over the heart rate of zebra fish larvae and in the blockage of sciatic nerve in mice. The results from this study support that the proper combination of natural excipients is promising in DDS, taking advantage of the biocompatibility, low cost, and diversity of lipids.

Nanostructured lipid carriers as robust systems for topical lidocaine-prilocaine release in dentistry.

In dental practice, local anesthesia causes pain, fear, and stress, and is frequently the reason that patients abandon treatment. Topical anesthetics are applied in order to minimize the discomfort caused by needle insertion and injection, and to reduce the symptoms of superficial trauma at the oral mucosa, but there are still no efficient commercially available formulations. Factorial design is a multivariate data analysis procedure that can be used to optimize the manufacturing processes of lipid nanocarriers, providing valuable information and minimizing development time. This work describes the use of factorial design to optimize a process for the preparation of nanostructured lipid carriers (NLC) based on cetyl palmitate and capric/caprylic triglycerides as structural lipids and Pluronic 68 as the colloidal stabilizer, for delivery of the local anesthetics lidocaine and prilocaine (both at 2.5%). The factors selected were the excipient concentrations, and three different responses were followed: particle size, polydispersity index and zeta potential. The encapsulation efficiency of the most effective formulations (NLC 2, 4, and 6) was evaluated by the ultrafiltration/centrifugation method. The formulations that showed the highest levels of encapsulation were tested using in vitro release kinetics experiments with Franz diffusion cells. The NLC6 formulation exhibited the best sustained release profile, with 59% LDC and 66% PLC released after 20h. This formulation was then characterized using different techniques (IR-ATR, DSC, DRX, TEM, and NTA) to obtain information about its molecular organization and its physicochemical stability, followed during 14months of storage at 25°C. This thorough pre-formulation study represents an important advance towards the development of an efficient pre-anesthetic for use in dentistry.

Delivery system for mefenamic acid based on the nanocarrier layered double hydroxide: Physicochemical characterization and evaluation of anti-inflammatory and antinociceptive potential.

PURPOSE: The anionic form of the drug mefenamic acid intercalated into the nanocarrier layered double hydroxide (LDH-Mef) was evaluated by anti-inflammatory and antinociceptive assays. METHODS: The LDH-Mef material was characterized by a set of physicochemical techniques, which was supported by Density Functional Theory calculations. The pharmacological effects of LDH-Mef (40 wt% of drug) were evaluated by hemolytic, anti-inflammatory activity and antinociceptive assays. RESULTS: In vivo assays were conducted for the first time in order to assess the LDH-Mef potential. The hemolytic effects decreased for the intercalated Mef as demonstrated by the higher tolerated hemolytic concentration (1.83 mM) compared to mefenamic acid (MefH), 0.48 mM. Pretreatment of animals with MefH or LDH-Mef reduced carrageenan-, dextran sulfate- and PGE2-induced paw edema. MefH or LDH-Mef also decrease total leucocytes and neutrophil counts of the peritoneal cavity after inflammation induction with carrageenan. In the nociception model, oral pretreatment with LDH-Mef reduced mechanical hypernociception carrageenan-induced after 3-4h and also the number of writhings induced by acetic acid. CONCLUSIONS: This work shows the increase of the anti-inflammatory and antinociceptive potential of the drug confined into the LDH, as well as, its hemolytic effect.