Linear correlation between rheological, mechanical and mucoadhesive properties of polycarbophil polymer blends for biomedical applications

Analysis of Key Factors for Evaluating Mucosal Adhesion Using Swine Buccal Tissue

The assessment of the mucoadhesive properties peak mucoadhesive force (Fmax) and work of mucoadhesion (Wmuc) with texture analyzers is a common in vitro method for analyzing formulation capabilities. Challenges arise in selecting and standardizing experimental conditions due to various variables influencing mucoadhesion. This complexity hampers direct product performance comparisons. In our study, we explored factors (contact force and time, probe speed and mucin in artificial saliva) impacting a model formulation's mucoadhesive capacity. Using Omcilon-A®Orabase on porcine buccal mucosa, we systematically varied experimental conditions, employing a statistical approach (Central Composite Design - CCD). Three variables (contact force, contact time, probe speed) and their interactions were assessed for their impact on Fmax and Wmuc. Results showed that contact time and force positively affected Fmax, while only contact time influenced Wmuc. In the mucin artificial saliva test, a force of 0.5 N, time of 600 s, and speed of 1 mm/s yielded optimal Fmax (0.587 N) and Wmuc (0.468 N.s). These conditions serve as a reference for comparing mucoadhesive properties of formulations for topical oral use.

Phase transforming in situ gels for sustained and controlled transmucosal drug delivery via the intravaginal route

Direct, reliable, controlled, and sustained drug delivery to female reproductive tract (FRT) remains elusive, with conventional dosage forms falling way short of the mark, leading to premature leakage, erratic drug delivery, and loss of compliance. Historically, the intravaginal route remains underserved by the pharmaceutical sector. To comprehensively address this, we turned our focus to phase-transforming sol-gels, using poloxamers, a thermosensitive polymer and, doxycycline (as hyclate salt, DOXH) as our model agent given its potential use in sexually transmitted infections (STIs). We further enhanced mucoadhesiveness through screening of differing viscosity grade hydroxypropyl methyl celluloses (HPMCs). The optimised sol-gels remained gelled at body temperature (<37 °C) and were prepared in buffer aligned to vaginal cavity pH and osmolality. Lead formulations were progressed based on their ability to retain key rheological properties, and acidic pH in the presence of simulated vaginal fluid (SVF). From a shelf-life perspective, DOXH stability, gelation temperature (Tsol-gel), and pH to three months (2-8 °C) was attained. In summary, the meticulously engineered, phase-transforming sol-gels provided sustained mucoretention despite dilution by vaginal fluid, paving the way for localised antimicrobial drug delivery at concentrations that potentially far exceed the minimum inhibitory concentration (MIC) for target STI-causing bacteria of the FRT.

Development of nanostructured environmentally responsive system containing hydroxypropyl methylcellulose for nose-to-brain administration of meloxicam

The intranasal administration of drugs using environmentally responsive formulations, employing a combination of hydroxypropyl methylcellulose (HPMC) and poloxamer 407 (P407), can result in release systems that may assist in the treatment of neurological diseases. Meloxicam, considered a potential adjuvant in the treatment of Alzheimer's disease, could be used in these platforms. The aim of this work was to develop a mucoadhesive, thermoresponsive, and nanostructured system containing HPMC for nose-to-brain administration of meloxicam. The initially selected systems were investigated for their rheological, mechanical, and micellar size characteristics. The systems were dilatant at 25 °C and pseudoplastic with a yield value at 37 °C, showing viscoelastic properties at both temperatures. The platform containing HPMC (0.1%, w/w) and P407 (17.5%, w/w) was selected and demonstrated good mucoadhesive properties, along with an appropriate in vitro release profile. HPMC could form a binary system with P407, displaying superior mucoadhesive and thermoresponsive properties for nose-to-brain meloxicam administration, indicating that the selected formulation is worthy of clinical studies.

Formulation optimization and evaluation of oromucosal in situ gel loaded with silver nanoparticles prepared by green biosynthesis

Treating oral diseases remains challenging as API is quickly washed out of the application site by saliva turnover and mouth movements. In situ gels are a class of application forms that present sol-gel transition's ability as a response to stimuli. Their tunable properties are provided using smart polymers responsible for stimuli sensitivity, often providing mucoadhesivity. In this study, antimicrobial in situ gels of thermosensitive and pH-sensitive polymers loaded with silver nanoparticles were prepared and evaluated. The nanoparticles were prepared by green synthesis using Agrimonia eupatoria L. extract. According to the data analysis, the in situ gel with the most promising profile contained 15 % of Pluronic® F-127, 0.25 % of methylcellulose, and 0.1 % of Noveon® AA-1. Pluronic® F-127 and methylcellulose significantly increased the viscosity of in situ gels at 37 °C and shear rates similar to speaking and swallowing. At 20 °C, a behavior close to a Newtonian fluid was observed while being easily injectable (injection force 13.455 ± 1.973 N). The viscosity of the formulation increased with temperature and reached 2962.77 ± 63.37 mPa·s (37 °C). A temperature increase led to increased adhesiveness and rigidity of the formulation. The critical sol-gel transition temperature at physiological pH was 32.65 ± 0.35 °C. 96.77 ± 3.26 % of Ag NPs were released by erosion and dissolution of the gel after 40 min. The determination of MIC showed effect against E. coli and S. aureus (0.0625 mM and 0.5000 mM, respectively). The relative inhibition zone diameter of the in situ gel was 73.32 ± 11.06 % compared to gentamicin sulfate. This work discusses the optimization of the formulation of novel antibacterial in situ gel for oromucosal delivery, analyses the impact of the concentration of excipients on the dependent variables, and suggests appropriate evaluation of the formulation in terms of its indication. This study offers a promising dosage form for local treatment of oral diseases.

Effect of extraction methods on the chemical, structural, and rheological attributes of fructan derived from Arctium lappa L. roots

The focus of this study was the evaluation of how extraction techniques impact the chemical, structural, and rheological attributes of fructans extracted from Arctium lappa L. roots. Three distinct extraction procedures were used, utilizing water as solvent, infusion extraction conducted at ambient temperature (25 °C for 5 min), thermal extraction employing reflux (100 °C for 2 h), and ultrasound-assisted extraction (50 °C for 1.38 h with a 158 W output). Chemical characterization by Nuclear Magnetic Resonance (NMR) and colorimetric analyses revealed the obtaining of inulin-type fructans (yield 83 %). The degree of polymerization (DP) was found to be the lowest for ultrasound-assisted extraction (14.38), followed by the room-temperature (20.41) and thermal (21.14) extraction techniques. None of the extraction techniques appeared to modify the molecular structure of the isolated compounds. In X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses, distinct crystallization patterns were observed for the room-temperature and thermal extraction techniques, though all fractions consistently exhibited characteristic bands of inulin-type fructan. Rheological assessments indicated a viscoelastic nature of the fractions, with those extracted thermally demonstrating a greater viscosity. This study shows that the choice of extraction method can influence the structural characteristics of inulin-type fructans derived from the burdock root.

Boosting the photodynamic activity of erythrosine B by using thermoresponsive and adhesive systems containing cellulose derivatives for topical delivery

Erythrosine displays potential photodynamic activity against microorganisms and unhealthy cells. However, erythrosine has high hydrophilicity, negatively impacting on permeation through biological membranes. Combining biological macromolecules and thermoresponsive polymers may overcome these erythrosine-related issues, enhancing retention of topically applied drugs. The aim of this work was to investigate the performance of adhesive and thermoresponsive micellar polymeric systems, containing erythrosine in neutral (ERI) or disodium salt (ERIs) states. Optimized combinations of poloxamer 407 (polox407) and sodium carboxymethylcellulose (NaCMC) or hydroxypropyl methylcellulose (HPMC) were used as platforms for ERI/ERIs delivery. The rheological and mechanical properties of the systems was explored. Most of the formulations were plastic, thixotropic and viscoelastic at 37 °C, with suitable gelation temperature for in situ gelation. Mechanical parameters were reduced in the presence of the photosensitizer, improving the softness index. Bioadhesion was efficient for all hydrogels, with improved parameters for mucosa in contrast to skin. Formulations composed of 17.5 % polox407 and 3 % HPMC or 1 % NaCMC with 1 % (w/w) ERI/ERIs could release the photosensitizer, reaching different layers of the skin/mucosa, ensuring enough production of cytotoxic species for photodynamic therapy. Functional micelles could boost the photodynamic activity of ERI and ERIs, improving their delivery and contact time with the cells.

Role of Bovine Serum Albumin Addition in Micellization and Gel Formation of Poloxamer 407

The combination of the thermoresponsive polymer and protein has demonstrated great promise in its applications in drug delivery and tissue engineering fields. This study described the impact of bovine serum albumin (BSA) on the micellization and sol-gel transition behaviors of poloxamer 407 (PX). The micellization of aqueous PX solutions with and without BSA was examined using isothermal titration calorimetry. In the calorimetric titration curves, the pre-micellar region, the transition concentration region, and the post-micellar region were observed. The presence of BSA had no noticeable impact on critical micellization concentration, but the inclusion of BSA caused the pre-micellar region to expand. In addition to studying the self-organization of PX at a particular temperature, the temperature-induced micellization and gelation of PX were also explored using differential scanning calorimetry and rheology. The incorporation of BSA had no discernible effect on critical micellization temperature (CMT), but it did affect gelation temperature (T_gel) and gel integrity of PX-based systems. The response surface approach illustrated the linear relation between the compositions and the CMT. The major factor affecting the CMT of the mixtures was the concentration of PX. The alteration of the T_gel and the gel integrity were discovered to be a consequence of the intricate interaction between PX and BSA. BSA mitigated the inter-micellar entanglements. Hence, the addition of BSA demonstrated a modulating influence on T_gel and a softening effect on gel integrity. Understanding the influence of serum albumin on the self-assembly and gelation of PX will enable the creation of thermoresponsive drug delivery and tissue engineering systems with controlled gelation temperatures and gel strength.

Cell penetrating peptides-functionalized Licochalcone-A-loaded PLGA nanoparticles for ocular inflammatory diseases: evaluation of in vitro anti-proliferative effects, stabilization by freeze-drying and characterization of an in-situ forming gel

Licochalcone-A (Lico-A) PLGA NPs functionalized with cell penetrating peptides B6 and Tet-1 are proposed for the treatment of ocular anti-inflammatory diseases. In this work, we report the in vitro biocompatibility of cell penetrating peptides-functionalized Lico-A-loaded PLGA NPs in Caco-2 cell lines revealing a non-cytotoxic profile, and their anti-inflammatory activity against RAW 264.7 cell lines. Given the risk of hydrolysis of the liquid suspensions, freeze-drying was carried out testing different cryoprotectants (e.g., disaccharides, alcohols, and oligosaccharide-derived sugar alcohol) to prevent particle aggregation and mitigate physical stress. As the purpose is the topical eye instillation of the nanoparticles, to reduce precorneal wash-out, increase residence time and thus Lico-A bioavailability, an in-situ forming gel based on poloxamer 407 containing Lico-A loaded PLGA nanoparticles functionalized with B6 and Tet-1 for ocular administration has been developed. Developed formulations remain in a flowing semi-liquid state under non-physiological conditions and transformed into a semi-solid state under ocular temperature conditions (35 °C), which is beneficial for ocular administration. The pH, viscosity, texture parameters and gelation temperature results met the requirements for ophthalmic formulations. The gel has characteristics of viscoelasticity, suitable mechanical and mucoadhesive performance which facilitate its uniform distribution over the conjunctiva surface. In conclusion, we anticipate the potential clinical significance of our developed product provided that a synergistic effect is achieved by combining the high anti-inflammatory activity of Lico-A delivered by PLGA NPs with B6 and Tet-1 for site-specific targeting in the eye, using an in-situ forming gel.

Poloxamer/Carboxymethyl Pullulan Aqueous Systems-Miscibility and Thermogelation Studies Using Viscometry, Rheology and Dynamic Light Scattering

Thermally-induced gelling systems based on Poloxamer 407 (PL) and polysaccharides are known for their biomedical applications; however, phase separation frequently occurs in mixtures of poloxamer and neutral polysaccharides. In the present paper, the carboxymethyl pullulan (CMP) (here synthesized) was proposed for compatibilization with poloxamer (PL). The miscibility between PL and CMP in dilute aqueous solution was studied by capillary viscometry. CMP with substitution degrees higher than 0.5 proved to be compatible with PL. The thermogelation of concentrated PL solutions (17%) in the presence of CMP was monitored by the tube inversion method, texture analysis and rheology. The micellization and gelation of PL in the absence or in the presence of CMP were also studied by dynamic light scattering. The critical micelle temperature and sol-gel transition temperature decrease with the addition of CMP, but the concentration of CMP has a peculiar influence on the rheological parameters of the gels. In fact, low concentrations of CMP decrease the gel strength. With a further increase in polyelectrolyte concentration, the gel strength increases until 1% CMP, then the rheological parameters are lowered again. At 37 °C, the gels are able to recover the initial network structure after high deformations, showing a reversible healing process.

Design as strategy for evaluation of the mechanical properties of binary mixtures composed of poly(methyl vinyl ether-alt-maleic anhydride) and Pluronic F127 for biomedical applications

The synergism between thermoresponsive and bioadhesive polymers can lead to the optimization of materials with enhanced mechanical and bioadhesive properties. Quality by Design can assure the understanding and control of formulation variables. In this approach, Design of Experiment has been widely utilized as an important strategy. Poly(methyl vinyl ether-alt-maleic anhydride) (PVMMA) is a bioadhesive polymer and Pluronic F127 (PF127) shows thermoresponsiveness. The association of these two polymers has been poorly investigated. The aim of this work was to study the mechanical, bioadhesive and rheological properties of polymer mixtures composed of PVMMA and PF127, in order to select the best conditions and formulations for biomedical applications. Textural properties (hardness, compressibility, adhesiveness, cohesiveness and elasticity), softness index, bioadhesion and rheological characteristics (flow and viscoelasticity) showed that 17.5-20% (w/w) PF127-polymer mixtures displayed improved values of the parameters. However, the rheological interaction parameter showed low synergism, due to the polymers' characteristics and system organization. The formulations displayed gelation temperatures suitable for administration, with improved bioadhesive properties mainly at 34 °C and suggests the formulations can be used for biomedical applications. DoE constituted an important tool to investigate these systems showing the main effects that significantly influence the binary mixtures.

Thermo and Photoresponsive Emulgel Loaded with Copaifera reticulata Ducke and Chlorophylls: Rheological, Mechanical, Photodynamic and Drug Delivery Properties in Human Skin

Recently, the number of new cases of cutaneous leishmaniasis has been of concern among health agencies. Research that offers new therapeutic alternatives is advantageous, especially those that develop innovative drugs. Therefore, this paper presents the incorporation of Copaifera reticulata Ducke and chlorophyll extract into Pluronic^®® F127 and Carbopol gels, under optimized polymer quantities. The chlorophyll extract (rich in photosensitizing compounds) was obtained by continuous-flow pressurized liquid extraction (PLE), a clean, environmentally friendly method. The system aims to act as as a leishmanicidal, cicatrizant, and antibiotic agent, with reinforcement of the photodynamic therapy (PDT) action. Rheological and mechanical analyses, permeation studies and bioadhesiveness analyses on human skin, and PDT-mediated activation of Staphylococcus aureus were performed. The emulgels showed gelation between 13° and 15 °C, besides pseudoplastic and viscoelastic properties. Furthermore, the systems showed transdermal potential, by releasing chlorophylls and C. reticulata Ducke into the deep layers of human skin, with good bioadhesive performance. The application of PDT reduced three logarithmic colony-forming units of S. aureus bacteria. The results support the potential of the natural drug for future clinical trials in treating wounds and cutaneous leishmania.

Photo-Phytotherapeutic Gel Composed of Copaifera reticulata, Chlorophylls, and k-Carrageenan: A New Perspective for Topical Healing

Chronic wound healing represents an impactful financial burden on healthcare systems. In this context, the use of natural products as an alternative therapy reduces costs and maintains effectiveness. Phytotherapeutic gels applied in photodynamic therapy (PDT) have been developed to act as topical healing medicines and antibiotics. The bioactive system is composed of Spirulina sp. (source of chlorophylls) and Copaifera reticulata oil microdroplets, both incorporated into a polymeric blend constituted by kappa-carrageenan (k-car) and F127 copolymer, constituting a system in which all components are bioactive agents. The flow behavior and viscoelasticity of the formulations were investigated. The photodynamic activity was accessed from studies of the inactivation of Staphylococcus aureus bacteria, the main pathogen of hospital relevance. Furthermore, in vivo studies were conducted using eighteen rabbits with dermatitis (grade III and IV) in both paws. The gels showed significant antibiotic potential in vitro, eliminating up to 100% of S. aureus colonies in the presence or absence of light. The k-car reduced 41% of the viable cells; however, its benefits were enhanced by adding chlorophyll and copaiba oil. The animals treated with the phytotherapeutic medicine showed a reduction in lesion size, with healing and re-epithelialization verified in the histological analyses. The animals submitted to PDT displayed noticeable improvement, indicating this therapy's viability for ulcerative and infected wounds. This behavior was not observed in the iodine control treatment, which worsened the animals' condition. Therefore, gel formulations were a viable alternative for future pharmaceutical applications, aiming at topical healing.

Design and Optimization of a Natural Medicine from Copaifera reticulata Ducke for Skin Wound Care

In this study, we developed a bioadhesive emulsion-filled gel containing a high amount of Copaifera reticulata Ducke oil-resin as a veterinary or human clinical proposal. The phytotherapeutic system had easy preparation, low cost, satisfactory healing ability, and fly repellency, making it a cost-effective clinical strategy for wound care and myiasis prevention. Mechanical, rheological, morphological, and physical stability assessments were performed. The results highlight the crosslinked nature of the gelling agent, with three-dimensional channel networks stabilizing the Copaifera reticulata Ducke oil-resin (CrD-Ore). The emulgel presented antimicrobial activity, satisfactory adhesion, hardness, cohesiveness, and viscosity profiles, ensuring the easy spreading of the formulation. Considering dermatological application, the oscillatory responses showed a viscoelastic performance that ensures emulgel retention at the action site, reducing the dosage frequencies. In Vivo evaluations were performed using a case report to treat ulcerative skin wounds aggravated by myiasis in calves and heifers, which demonstrated healing, anti-inflammatory, and repellent performance for the emulsion-filled gel. The emulgel preparation, which is low in cost, shows promise as a drug for wound therapy.

Thermosensitive Polymer Blend Composed of Poloxamer 407, Poloxamer 188 and Polycarbophil for the Use as Mucoadhesive In Situ Gel

Herein, thermosensitive blends of poloxamer 407 (P407)/poloxamer 188 (P188)/polycarbophil (PCB) were developed in terms of maximized content of PCB (a mucoadhesive polymer) and desired temperature-dependent rheological properties of the blends as in situ gelling matrices. Maximizing PCB content while achieving the preferable rheological characteristics was accomplished through the Box–Behnken design. The quantitative effect of the polymer composition in the blends on the thermosensitive characteristics was evaluated using the fitted design model and the corresponding surface plots. The optimized P407/P188/PCB blend (OPT) was the mixture of 20.000, 7.349 and 0.595% (w/w) of P407, P188, and PCB, respectively. The thermosensitive micellization of OPT was investigated using differential scanning calorimetry which revealed an overlapping double endothermic peak caused by the temperature-induced micellization of pure micelles in co-existence with the micelles with attached PCB. Mixing PCB with the P407/P188 matrix promoted a more intense mucoadhesion of the blend. After incorporating metronidazole, a model hydrophilic drug, into OPT, the temperature-dependent characteristics of the hydrogel did not change. Metronidazole release from OPT was sustained by an anomalous mechanism. This optimal ternary hydrogel benefiting from thermosensitive gelling and mucoadhesive matrix might be used as a viable platform for mucoadhesive in situ gelling drug delivery.

Drug Delivery Platforms Containing Thermoresponsive Polymers and Mucoadhesive Cellulose Derivatives: A Review of Patents

Nowadays, the development of mucoadhesive systems for drug delivery has gained keen interest, with enormous potential in applications through different routes. Mucoadhesion characterizes an attractive interaction between the pharmaceutical dosage form and the mucosal surface. Many polymers have shown the ability to interact with mucus, increasing the residence time of local and/or systemic administered preparations, such as tablets, patches, semi-solids, and micro and nanoparticles. Cellulose is the most abundant polymer on the earth. It is widely used in the pharmaceutical industry as an inert pharmaceutical ingredient, mainly in its covalently modified forms: methylcellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and carboxymethylcellulose salts. Aiming to overcome the drawbacks of oral, ocular, nasal, vaginal, and rectal routes and thereby maintaining patient compliance, innovative polymer blends have gained the interest of the pharmaceutical industry. Combining mucoadhesive and thermoresponsive polymers allows for simultaneous in situ gelation and mucoadhesion, thus enhancing the retention of the system at the site of administration and drug availability. Thermoresponsive polymers have the ability to change physicochemical properties triggered by temperature, which is particularly interesting considering the physiological temperature. The present review provides an analysis of the main characteristics and applications of cellulose derivatives as mucoadhesive polymers and their use in blends together with thermoresponsive polymers, aiming at platforms for drug delivery. Patents were reviewed, categorized, and discussed, focusing on the applications and pharmaceutical dosage forms using this innovative strategy. This review manuscript also provides a detailed introduction to the topic and a perspective on further developments.

Injectable and adhesive hydrogels for dealing with wounds

INTRODUCTION

The development of wound dressing materials that combine healing properties, ability to self-repair the material damages, skin-friendly adhesive nature, and competent mechanical properties have surpassing functional importance in healthcare. Due to their specificity, hydrogels have been recognized as a new gateway in biological materials to treat dysfunctional tissues. The design and creation of injectable hydrogel-based scaffolds have extensively progressed in recent years to improve their therapeutic efficacy and to pave the way for their easy minimally invasive administration. Hence, injectable hydrogel biomaterials have been prepared to eventually translate into minimally invasive therapy and pose a lasting effect on regenerative medicine.

AREAS COVERED

This review highlights the recent development of adhesive and injectable hydrogels that have applications in wound healing and wound dressing. Such hydrogel materials are not only expected to improve therapeutic outcomes but also to facilitate the easy surgical process in both wound healing and dressing.

EXPERT OPINION

Wound healing seems to be an appealing approach for treating countless life-threatening disorders. With the average increase of life expectancy in human societies, an increase in demand for injectable skin replacements and drug delivery carriers for chronic wound healing is expected.

Clinical outcomes in adults' subjects with aphthous stomatitis treated with an oral hyaluronic acid-based medical device

BACKGROUND

Oral mucosal ulcers are quite common in an otherwise healthy population and can determine a real worsening of the quality of life. Conventional therapy is not appropriate since ulcers often recur and, even if not needed, therapy lasting not less than 2-3 weeks carries a high risk of serious side effects. The use of hyaluronic acid applied as an adhesive gel over the lesions seems to have potential in terms of efficacy and the avoidance of side effects. Of course, hyaluronic acid-based formulations show different effects and tolerability.

METHODS

In our study, we retrospectively report the results obtained using a medical device, Bloxaphte®, applied for 14 days to counteract ulcers in adults.

RESULTS

Treatment with the HA-based oral gel determined better results both in terms of the number of oral lesions and in terms of lesion sizes. Regarding the number of lesions, the results are significant even after 6 days of treatment, while 3 days are enough to differentiate the two groups with respect to lesion sizes.

CONCLUSIONS

Our data clearly demonstrate the healing capability and safety profile of the product in reducing the number and size of the ulcers within the first week of daily application.

Mucoadhesive, Thermoreversible Hydrogel, Containing Tetracaine-Loaded Nanostructured Lipid Carriers for Topical, Intranasal Needle-Free Anesthesia

Recent advances have been reported for needle-free local anesthesia in maxillary teeth by administering a nasal spray of tetracaine (TTC) and oxymetazoline, without causing pain, fear, and stress. This work aimed to assess whether a TTC-loaded hybrid system could reduce cytotoxicity, promote sustained permeation, and increase the anesthetic efficacy of TTC for safe, effective, painless, and prolonged analgesia of the maxillary teeth in dental procedures. The hybrid system based on TTC (4%) encapsulated in nanostructured lipid carriers (NLC) and incorporated into a thermoreversible hydrogel of poloxamer 407 (TTCNLC-HG4%) displayed desirable rheological, mechanical, and mucoadhesive properties for topical application in the nasal cavity. Compared to control formulations, the use of TTCNLC-HG4% slowed in vitro permeation of the anesthetic across the nasal mucosa, maintained cytotoxicity against neuroblastoma cells, and provided a three-fold increase in analgesia duration, as observed using the tail-flick test in mice. The results obtained here open up perspectives for future clinical evaluation of the thermoreversible hybrid hydrogel, which contains TTC-loaded NLC, with the aim of creating an effective, topical, intranasal, needle-free anesthesia for use in dentistry.

Design and Optimization of Stimuli-responsive Emulsion-filled Gel for Topical Delivery of Copaiba Oil-resin

This study presents a phytotherapeutic emulsion-filled gel design composed of Pluronic® F127, Carbopol® C934P, and high level of copaiba oil-resin (PHY-ECO). Mathematical modeling and response surface methodology (RSM) were employed to access the optimal ratio between the oil and the polymer gel-matrix constituents. The chemometric approach showed robust mechanical and thermoresponsive properties for emulsion gel. The model predicts viscosity parameters at 35.0°C (skin temperature) from PHY-ECOs. Optimized PHY-ECOs were described by 18-20% (w/w) F127, 0.25% (w/w) C934P, and 15% (w/w) copaiba oil-resin, and showed interfacial layers properties that led to high physicochemical stability. Besides, it had thermal stimuli-responsive that led large viscosity range before and after skin administration, observed by oscillatory rheology. These behaviors give the optimized smart PHY-ECO high design potential to be used as a pharmaceutical platform for CO delivery, focusing on the anti-inflammatory therapy and skin wound care.

Ferromagnetic soft catheter robots for minimally invasive bioprinting

In vivo bioprinting has recently emerged as a direct fabrication technique to create artificial tissues and medical devices on target sites within the body, enabling advanced clinical strategies. However, existing in vivo bioprinting methods are often limited to applications near the skin or require open surgery for printing on internal organs. Here, we report a ferromagnetic soft catheter robot (FSCR) system capable of in situ computer-controlled bioprinting in a minimally invasive manner based on magnetic actuation. The FSCR is designed by dispersing ferromagnetic particles in a fiber-reinforced polymer matrix. This design results in stable ink extrusion and allows for printing various materials with different rheological properties and functionalities. A superimposed magnetic field drives the FSCR to achieve digitally controlled printing with high accuracy. We demonstrate printing multiple patterns on planar surfaces, and considering the non-planar surface of natural organs, we then develop an in situ printing strategy for curved surfaces and demonstrate minimally invasive in vivo bioprinting of hydrogels in a rat model. Our catheter robot will permit intelligent and minimally invasive bio-fabrication.

Emulgels Containing Propolis and Curcumin: The Effect of Type of Vegetable Oil, Poly(Acrylic Acid) and Bioactive Agent on Physicochemical Stability, Mechanical and Rheological Properties

Emulgels are obtained by the entrapment of an organic phase within a three-dimensional network built by hydrophilic molecules. Polymers based on cross-linked poly(acrylic acid) have been utilized as gel matrices, improving adhesiveness, rheological and mechanical performance. Propolis (PRP) produced by Apis mellifera L. bees displays a wide range of biological activities. Together with curcumin (CUR), they may show synergic anti-inflammatory, antioxidant and antimicrobial action on skin disorders. This work investigated the effect of vegetable oils (sweet almond, andiroba, and passion fruit) with regard to the physicochemical properties of emulgels composed of Carbopol 934P^®, Carbopol 974P^®, or polycarbophil aiming the CUR and PRP delivery. Physicochemical stability enabled the selection of systems containing passion fruit or andiroba oil. Mechanical and rheological characteristics provided rational comprehension of how vegetable oils and bioactive agents affect the structure of emulsion gels. All formulations exhibited high physiochemical stability and properties dependent on the polymer type, oil, and bioactive agent. Formulations displayed pseudoplastic, thixotropic and viscoelastic properties. Emulgels containing andiroba oil were the most stable systems. Carbopol 934P^® or polycarbophil presence resulted in formulations with improved smoothness and mechanical properties. Systems containing andiroba oil and one of these two polymers are promising for further investigations as topical delivery systems of CUR and/or PRP on the skin and mucous membranes.

Preclinical evaluation of methotrexate-loaded polyelectrolyte complexes and thermosensitive hydrogels as treatment for rheumatoid arthritis

This work proposes new methotrexate (MTX) loaded drug delivery systems (DDS) to treat rheumatoid arthritis via the intra-articular route: a poloxamer based thermosensitive hydrogel (MTX-HG), oligochitosan and hypromellose phthalate-based polyelectrolyte complexes (MTX-PEC) and their association (MTX-PEC-HG). MTX-PEC showed 470 ± 166 nm particle size, 0.298 ± 0.108 polydispersity index, +26 ± 2 mV and 74.3 ± 5.8% MTX efficiency entrapment and particle formation was confirmed by infrared spectroscopy and thermal analysis. MTX-HG and MTX-PEC-HG gelled at 36.7°C. MTX drug release profile was prolonged for MTX-HG and MTX-PEC-HG, and faster for MTX-PEC and free MTX. The in vivo effect of the MTX-DDSs systems was evaluated in induced arthritis rats as single intra-articular dose. The assessed parameters were the mechanical nociceptive threshold, the plasmatic IL-1β level and histological analysis of the tibiofemoral joint. MTX-HG and MTX-PEC-HG performance were similar to free MTX and worse than oral MTX, used as positive control. All DDSs showed some irritative effect, for which further studies are required. MTX-PEC was the best treatment on recovering cartilage damage and decreasing allodynia. Thus, MTX-PEC demonstrated potential to treat rheumatoid arthritis, with the possibility of decreasing the systemic exposure to the drug.

Preclinical study of methotrexate-based hydrogels versus surfactant based liquid crystal systems on psoriasis treatment

Psoriasis is an autoimmune, inflammatory and chronic skin disease in which cell growth and proliferation are increased, causing erythema, lesions and skin's peeling. Oral methotrexate (MTX) is the first-choice drug when phototherapy or retinoid treatment are not effective. Topical administration can be advantageous to better orientate the drug's delivery; however, the stratum corneum performs as a barrier for hydrofilic drugs penetration. This study sought to evaluate two different types of vehicles for MTX on the psoriasis treatment - hydrogel and liquid crystal systems (LCs). Lamellar and hexagonal liquid crystalline phases were selected from a ternary phase diagram based on polysorbate 80, isopropyl miristate and water. The hydrogel was based on alkylated carbomer (ACH). Rheological analysis showed ACH was more elastic than lamellar and hexagonal phases. ACH interacted better with pig skin than LCs in bioadhesion assay. Preclinical study revealed the ACH decreased inflammation in mice with induced psoriasis, being as effective as dexamethasone to regulate epidermis thickness, COX-2 and myeloperoxidase activity and TNF-α level, while LCs demonstrated inflammatory effect. Therefore, MTX-loaded hydrogel based platforms are indicated for local treatment of psoriasis and present great potential for further studies.

Thermoresponsive Hydrogel-Loading Aluminum Chloride Phthalocyanine as a Drug Release Platform for Topical Administration in Photodynamic Therapy

Phthalocyanine aluminum chloride (Pc) is a clinically viable photosensitizer (PS) to treat skin lesions worsened by microbial infections. However, this molecule presents a high self-aggregation tendency in the biological fluid, which is an in vivo direct administration obstacle. This study proposed the use of bioadhesive and thermoresponsive hydrogels comprising triblock-type Pluronic F127 and Carbopol 934P (FCarb) as drug delivery platforms of Pc (FCarbPc)-targeting topical administration. Carbopol 934P was used to increase the F127 hydrogel adhesion on the skin. Rheological analyses showed that the Pc presented a low effect on the hydrogel matrix, changing the gelation temperature from 27.2 ± 0.1 to 28.5 ± 0.9 °C once the Pc concentration increases from zero to 1 mmol L^-1. The dermatological platform showed matrix erosion effects with the release of loaded Pc micelles. The permeation studies showed the excellent potential of the FCarb platform, which allowed the partition of the PS into deeper layers of the skin. The applicability of this dermatological platform in photodynamic therapy was evaluated by the generation of reactive species which was demonstrated by chemical photodynamic efficiency assays. The low effect on cell viability and proliferation in the dark was demonstrated by in vitro assays using L929 fibroblasts. The FCarbPc fostered the inhibition of Staphylococcus aureus strain, therefore demonstrating the platform's potential in the treatment of dermatological infections of microbial nature.

Towards the advance of a novel iontophoretic patch for needle-free buccal anesthesia

The aim of this work was to develop a mucoadhesive iontophoretic patch for anesthetic delivery in the buccal epithelium. The patch was comprised of three different layers, namely i) drug release (0.64 cm²); ii) mucoadhesive (1.13 cm²); and iii) backing (1.13 cm²). Prilocaine and lidocaine hydrochlorides were used as model drugs (1:1 ratio, 12.5 mg per unit). An anode electrode (0.5 cm² spiral silver wire) was placed in between the drug release and mucoadhesive/backing layers to enable iontophoresis. Surface microscopy; mechanical and in vitro mucoadhesive properties; drug release kinetics and mechanism; and drug permeation through the porcine esophageal epithelium were assessed. Topographic analysis evidenced differences in the physical structures for the several layers. All layers presented suitable handling properties i.e., flexibility, elasticity and resistance. Both the release and mucoadhesive layers presented features of a soft and tough material, while the backing layer matched the characteristics of a hard and brittle material. A synergy between the drug release and mucoadhesive layers on the mucoadhesive force and work of adhesion of the tri-layered patch was observed. Passive drug release of both drugs fitted to First-order, Hixson-Crowell and Weibull kinetic models; and the release mechanism was attributed to anomalous transport. Iontophoresis remarkably enhanced the permeation of both drugs, but mainly prilocaine through the mucosa as evidenced by the permeability coefficient parameter (3.0-fold). The amount of these amino amide salts retained in the mucosa were also equally enhanced (4.7-fold), while the application of a tiny constant electric current (1 mA·cm^-2·h^-1) significantly decreased the lag time for lidocaine permeation by about 45%. In view of possible in vitro / in vivo correlations, the buccal iontophoretic patch displays a promising strategy for needle-free and patient-friendly local anesthesia in dentistry.

Sustained-release hydrogels of ivermectin as alternative systems to improve the treatment of cutaneous leishmaniasis

Background: Leishmaniasis is a neglected tropical disease and its cutaneous form manifests as ulcers or nodules, generally in exposed parts of the body. This work aimed to develop ivermectin (IVM) thermosensitive hydrogels as topical formulations to improve cutaneous leishmaniasis treatment. Materials & methods: Hydrogels based on poloxamers 407 and 188 with different concentrations of IVM were prepared and rheologically characterized. The IVM release profiles were obtained and mathematically analyzed using the Lumped model. Results: The formulation containing 1.5% w/w of IVM presented an adequate gelling temperature, an optimal complex viscosity and elastic modulus. Hydrogels allowed to modulate the release of IVM. Conclusion: IVM thermosensitive hydrogels can be considered a valuable alternative to improve the treatment of cutaneous leishmaniasis.

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.

Design of a nanostructured mucoadhesive system containing curcumin for buccal application: from physicochemical to biological aspects

Mucoadhesive nanostructured systems comprising poloxamer 407 and Carbopol 974P® have already demonstrated good mucoadhesion, as well as improved mechanical and rheological properties. Curcumin displays excellent biological activity, mainly in oral squamous cancer; however, its physicochemical characteristics hinder its application. Therefore, the aim of this study was to develop nanostructured formulations containing curcumin for oral cancer therapy. The photophysical interactions between curcumin and the formulations were elucidated by incorporation kinetics and location studies. They revealed that the drug was quickly incorporated and located in the hydrophobic portion of nanometer-sized polymeric micelles. Moreover, the systems displayed plastic behavior with rheopexy characteristics at 37 °C, viscoelastic properties and a gelation temperature of 36 °C, which ensures increased retention after application in the oral cavity. The mucoadhesion results confirmed the previous findings with the nanostructured systems showing a residence time of 20 min in porcine oral mucosa under flow system conditions. Curcumin was released after 8 h and could permeate through the porcine oral mucosa. Cytotoxicity testing revealed that the formulations were selective to cancer cells over healthy cells. Therefore, these systems could improve the physicochemical characteristics of curcumin by providing improved release and permeation, while selectivity targeting cancer cells.

Design and characterization of an organogel system containing ascorbic acid microparticles produced with propolis by-product

This study aimed to prepare and characterize organogels containing microparticles of ascorbic acid (AA) obtained from propolis by-product. The formulations F1 (5% of microparticles) and F2 (10% of microparticles) were evaluated regarding rheological and textural properties, antioxidant and radical scavenging activity, in vitro release and cellular studies. The organogels showed plastic flow behavior and rheopexy. The textural parameters were within acceptable values for semisolid formulations. The antioxidant capacity of organogels F1 and F2 by the DPPH assay demonstrated IC₅₀ ranging from 1523.59 to 1166.97 μg/mL, respectively. For the FRAP assay, the values found were 842.88 and 956.14 μmol of FSE/g formulation, respectively. Good scavenging activity against nitrogen species was observed. The concentration of 63 μg/mL did not present toxicity on HaCaT and HFF-1 cells. In vitro release profile of AA from organogels showed a slow pattern of drug release, mainly for F2. Therefore, the proposed organogel containing AA microparticles with propolis by-product matrix represents a promising platform for topical drug delivery with antioxidant effect.

Contact-free determination of viscosity in multiple parallel samples

Viscosity is an inherent characteristic of fluids and is therefore an important parameter in many different processes. Current methods to measure viscosity involve direct contact with the liquid sample, which is often undesirable. Here we present a simple, precise and robust contact-free method to determine viscosity, using a single drive motor, inexpensive components and disposable sample vessels. The measurement principle involves the detection of viscosity-dependent angular positions in a rotating liquid relative to the direction of centrifugal acceleration in an orbitally shaken vessel. The signal can be detected using different optical methods, as shown here using fluorescence and transmitted light. The sensitivity of the system can be adjusted over a wide range by varying the sample volume or the shaking diameter, and multiple samples can be analysed in parallel. This novel viscometer is also applicable to characterize non-Newtonian shear rate-dependent fluids.

Poloxamer-based in situ gelling thermoresponsive systems for ocular drug delivery applications

In situ gels have recently received interest as ocular drug delivery vehicles because they combine the merits of easy instillation and sustained drug release. In this review, we focus on the use of poloxamers as in situ gelling systems in ocular drug delivery because of their thermoresponsive gelling behaviour, biocompatibility, and ease of sterilisation. Furthermore, the sol-gel transition temperature, mucoadhesive properties, and drug release profiles of poloxamer-based in situ gels can be finely tuned, enabling them to be used as vehicles for the delivery of small and large drug molecules to treat diseases of the anterior and posterior segments of the eye. Poloxamer-based ocular products have already found their way to the pharmaceutical market, but remain a potential arena for further investigation and commercial exploitation.

Adhesive thermosensitive gels for local delivery of viral vectors

Local delivery of viral vectors can enhance the efficacy of therapies by selectively affecting necessary tissues and reducing the required vector dose. Pluronic F127 is a thermosensitive polymer that undergoes a solution-gelation (sol-gel) transition as temperature increases and can deliver vectors without damaging them. While pluronics can be spread over large areas, such as the surface of an organ, before gelation, they lack sufficient adhesivity to remain attached to some tissues, such as the surface of the heart or mucosal surfaces. Here, we utilized blends of pluronic F127 and polycarbophil (PCB), a mucoadhesive agent, to provide the necessary adhesivity for local delivery of viral vectors to the cardiac muscle. The effects of PCB concentration on adhesive properties, sol-gel temperature transition and cytocompatibility were evaluated. Rheological studies showed that PCB decreased the sol-gel transition temperature at concentrations >1% and increased the adhesive properties of the gel. Furthermore, these gels were able to deliver viral vectors and transduce cells in vitro and in vivo in a neonatal mouse apical resection model. These gels could be a useful platform for delivering viral vectors over the surface of organs where increased adhesivity is required.

Electrospun Alginate Fibers: Mixing of Two Different Poly(ethylene oxide) Grades to Improve Fiber Functional Properties

The aim of the present work was to investigate how the molecular weight (MW) of poly(ethylene oxide) (PEO), a synthetic polymer able to improve alginate (ALG) electrospinnability, could affect ALG-based fiber morphology and mechanical properties. Two PEO grades, having different MWs (high, h-PEO, and low, l-PEO) were blended with ALG: the concentrations of both PEOs in each mixture were defined so that each h-PEO/l-PEO combination would show the same viscosity at high shear rate. Seven ALG/h-PEO/l-PEO mixtures were prepared and characterized in terms of viscoelasticity and conductivity and, for each mixture, a complex parameter rH/rL was calculated to better identify which of the two PEO grades prevails over the other in terms of exceeding the critical entanglement concentration. Thereafter, each mixture was electrospun by varying the process parameters; the fiber morphology and mechanical properties were evaluated. Finally, viscoelastic measurements were performed to verify the formation of intermolecular hydrogen bonds between the two PEO grades and ALG. rH/rL has been proved to be the parameter that better explains the effect of the electrospinning conditions on fiber dimension. The addition of a small amount of h-PEO to l-PEO was responsible for a significant increase in fiber mechanical resistance, without affecting the nano-scale fiber size. Moreover, the mixing of h-PEO and l-PEO improved the interaction with ALG, resulting in an increase in chain entanglement degree that is functional in the electrospinning process.

Coated electrospun alginate-containing fibers as novel delivery systems for regenerative purposes

Aim

The aim of the present work was to develop biodegradable alginate (ALG)-containing fibrous membranes intended for tissue repair, acting as both drug delivery systems and cell growth guidance.

Methods

Membranes were prepared by electrospinning. Since ALG can be electrospun only when blended with other spinnable polymers, dextran (DEX) and polyethylene oxide (PEO) were investigated as process adjuvants. ALG/DEX mixtures, characterized by different rheological and conductivity properties, were prepared in phosphate buffer or deionized water; surfactants were added to modulate polymer solution surface tension. The Design of Experiments (DoE) approach (full factorial design) was used to investigate the role of polymer solution features (rheological properties, surface tension, and conductivity) on electrospun fiber morphology. A high viscosity at 1,000 s^-1 (1.3-1.9 Pa.s) or a high pseudoplasticity index (≥1.7), combined with a low surface tension (30-32 mN/m) and a low conductivity (800-1,000 μS/cm), was responsible for the production of ALG/DEX homogeneous fibers. Such ranges were successfully employed for the preparation of ALG-containing fibers, using PEO, instead of DEX, as process adjuvant. ALG/DEX and ALG/PEO fibers were subsequently subjected to cross-linking/coating processes to make them slowly biodegradable in aqueous medium. In particular, ALG/PEO fibers were cross-linked and coated with CaCl₂/chitosan solutions in water/ethanol mixtures. Due to DEX high content, ALG/DEX fibers were soaked in a polylactide-co-glycolide (PLGA) solution in ethyl acetate.

Results

Both cross-linking and coating processes made fibers insoluble in physiological medium and produced an increase in their mechanical resistance, assessed by means of a tensile test. PLGA-coated ALG/DEX and chitosan-coated ALG/PEO fibers were biocompatible and able to support fibroblast adhesion.

Conclusion

The DoE approach allowed to draw up guidelines useful for the preparation of homogeneous fibers, starting from mixtures of ALG and non-ionic polymers. Such fibers, upon coating, resulted to be good cell substrates, allowing cell adhesion and growth.

Levobupivacaine Thermogel for Long-acting Analgesia

The adequate management of analgesia, by pharmacological methods or not, is a great challenge. Local anesthetics are used for pain relief, mainly by parenteral, intramuscular, catheter, and other routes of administration. The use of in situ forming systems becomes an alternative for the control of pain. The present research investigates development of thermogels containing poloxamer and levobupivacaine. All formulations were prepared by the cold method; the compatibilities of the excipients were evaluated by DSC, rheology and viscosities, transition temperature, syringeability, release kinetics, and permeation. The compatibility of the tested excipients with the drug was initially observed; all formulations had a viscosity increase at 37°C. Different delivery rates were observed in both the release and permeation studies. The developed systems maintained the in vitro release of the drug for a long period, likely decreasing side effects in vivo and avoiding the need for supplementary analgesia by other routes.