A mucoadhesive patch loaded with freeze-dried liposomes for the local treatment of oral tumors.

Oral cancers affect millions of people globally, with increasing incidences among adults aged 35 and above. Poor drug uptake by lesions in the oral cavity following systemic administration, as well as limited localized treatment modalities for oral tumors, result in poor patient quality of life and high mortality. Here, we describe a solid, dissolvable, bioadhesive alginate patch containing freeze-dried doxorubicin-loaded liposomes as a local treatment for oral tumors located on the tongue. By varying the alginate-to-liposome ratio in the mucoadhesive patch, we could control the degree of bioadhesion to the tongue and the release profile of the drug-loaded liposomes from the matrix. In vitro, exposing squamous cell carcinoma (SCC) to the alginate mucoadhesive patch or tablet resulted in dose-dependent cancer-cell death. In vivo, the efficacy of the local treatment was demonstrated in mice bearing orthotopic SCC tumors in the tongue. The bioadhesive patch, applied directly above the lesion, significantly reduced the tumor size and treatment-associated side effects compared to implanted patches or systemic drug administration. This study demonstrates that local bioadhesive therapies are effective in treating cancers of the oral cavity.

Print-and-Grow within a Novel Support Material for 3D Bioprinting and Post-Printing Tissue Growth.

3D bioprinting holds great promise for tissue engineering, with extrusion bioprinting in suspended hydrogels becoming the leading bioprinting technique in recent years. In this method, living cells are incorporated within bioinks, extruded layer by layer into a granular support material followed by gelation of the bioink through diverse cross-linking mechanisms. This approach offers high fidelity and precise fabrication of complex structures mimicking living tissue properties. However, the transition of cell mass mixed with the bioink into functional native-like tissue requires post-printing cultivation in vitro. An often-overlooked drawback of 3D bioprinting is the nonuniform shrinkage and deformation of printed constructs during the post-printing tissue maturation period, leading to highly variable engineered constructs with unpredictable size and shape. This limitation poses a challenge for the technology to meet applicative requirements. A novel technology of "print-and-grow," involving 3D bioprinting and subsequent cultivation in κ-Carrageenan-based microgels (CarGrow) for days is presented. CarGrow enhances the long-term structural stability of the printed objects by providing mechanical support. Moreover, this technology provides a possibility for live imaging to monitor tissue maturation. The "print-and-grow" method demonstrates accurate bioprinting with high tissue viability and functionality while preserving the construct's shape and size.

Insights into the formation mechanisms and properties of pectin hydrogel physically cross-linked with chitosan nanogels.

This study explores hydrogels based on the physical interaction between soluble pectin and chitosan nanogels. A simple technique for creating chitosan nanogels of controllable size was developed based on a two-step process: physical cross-linking with tripolyphosphate (TPP) and chemical cross-linking with genipin. The particles were stable at acidic pH, which allowed hydrogel formation. Thixotropy experiments demonstrated that the concentration but not the size of the nanogels strongly affected the gel shear modulus. The influence of the post-assembly conditions, including exposure to monovalent salts (NaCl, NaI, and NaF) and pH (2.5 or 5.5), on the gel swelling and mechanical properties was studied. Small angle x-ray scattering (SAXS) results provide evidence that these physical hydrogels are indeed a cross-linked network. These experiments provided insights into the influence of hydrogen bonds and electrostatic interactions on the gel network.

Hybrid Acrylated Chitosan and Thiolated Pectin Cross-Linked Hydrogels with Tunable Properties.

We developed and characterized a new hydrogel system based on the physical and chemical interactions of pectin partially modified with thiol groups and chitosan modified with acrylate end groups. Gelation occurred at high pectin thiol ratios, indicating that a low acrylated chitosan concentration in the hydrogel had a profound effect on the cross-linking. Turbidity, Fourier transform infrared spectroscopy, and free thiol determination analyses were performed to determine the relationships of the different bonds inside the gel. At low pH values below the pKa of chitosan, more electrostatic interactions were formed between opposite charges, but at high pH values, the Michael-type addition reaction between acrylate and thiol took place, creating harder hydrogels. Swelling experiments and Young's modulus measurements were performed to study the structure and properties of the resultant hydrogels. The nanostructure was examined using small-angle X-ray scattering. The texture profile analysis showed a unique property of hydrogel adhesiveness. By implementing changes in the preparation procedure, we controlled the hydrogel properties. This hybrid hydrogel system can be a good candidate for a wide range of biomedical applications, such as a mucosal biomimetic surface for mucoadhesive testing.

Inclusion of Cross-Linked Elastin in Gelatin/PEG Hydrogels Favourably Influences Fibroblast Phenotype.

The capacity of a biomaterial to innately modulate cell behavior while meeting the mechanical property requirements of the implant is a much sought-after goal within bioengineering. Here we covalently incorporate soluble elastin into a gelatin-poly (ethylene glycol) (PEG) hydrogel for three-dimensional (3D) cell encapsulation to achieve these properties. The inclusion of elastin into a previously optimized gelatin-PEG hydrogel was then evaluated for effects on entrapped fibroblasts, with the aim to assess the hydrogel as an extracellular matrix (ECM)-mimicking 3D microenvironment for cellular guidance. Soluble elastin was incorporated both physically and covalently into novel gelatin/elastin hybrid PEG hydrogels with the aim to harness the cellular interactivity and mechanical tunability of both elastin and gelatin. This design allowed us to assess the benefits of elastin-containing hydrogels in guiding fibroblast activity for evaluation as a potential dermal replacement. It was found that a gelatin-PEG hydrogel with covalently conjugated elastin, supported neonatal fibroblast viability, promoted their proliferation from 7.3% to 13.5% and guided their behavior. The expression of collagen alpha-1(COL1A1) and elastin in gelatin/elastin hybrid gels increased 16-fold and 6-fold compared to control sample at day 9, respectively. Moreover, cells can be loaded into the hydrogel precursor solution, deposited, and the matrix cross-linked without affecting the incorporated cells adversely, thus enabling a potential injectable system for dermal wound healing.

The effect of freeze-drying on mucoadhesion and transport of acrylated chitosan nanoparticles.

Nanoparticle-based mucosal drug delivery is a promising method to increase the residence time of a drug in the mucosa. It is known that the stability of polysaccharide-based nanoparticles in aqueous solutions is limited, due to hydrolysis; hence the long-term stability of a formulation is usually improved by freeze-drying. The aim of this study was to investigate the effect of cryoprotection and freeze-drying on the physical and chemical properties of mucoadhesive acrylated chitosan (ACS) nanoparticles including the potential of these carriers to deliver drugs. The results showed that the most effective cryoprotection was achieved using sucrose. The incorporation of a hydrophilic macromolecular drug, dextran sulfate, increased the nanoparticle size and decreased the zeta potential for both fresh and freeze-dried nanoparticle formulations. In addition, the freeze-dried nanoparticles presented penetration across a mucus gel layer and the flow through technique revealed that short term mucoadhesive properties were not impaired. ACS nanoparticles were able to deliver a model drug across a mucin gel layer but could not improve drug penetration through the triple co-culture cell model that was used in order to mimic the small intestine epithelium.

Shear thinning pectin hydrogels physically cross-linked with chitosan nanogels.

The development of a polymer-nanogel hydrogel based on a pair of polysaccharides is reported for the first time. This new hydrogel exhibits self-healing properties due to physical interactions between soluble pectin chains and chitosan nanogels. The nanogels act as crosslinking agents between pectin chains, leading to the formation of thermos-responsive hydrogel. Due to the dynamic interactions between the chains and the nanogels, the formed network dissociate under applied shear, allowing the hydrogel to flow. Moreover, elimination of the applied shear results in exceptionally fast and comprehensive recovery of the storage modulus, reverting the mixture back into solid form. The viscosity and Young modulus increased with the nanogels concentration while the equilibrium swelling decreased as the nanogels concentration increased suggesting a direct relation between the cross-linking degree and nanogel content. This novel hydrogel displays network recovery suitable for injectable biomedical applications, while benefiting from the advantages of nanogels as carriers.

Mucoadhesive Hybrid Polymer/Liposome Pastes Based on Modified Polysaccharides.

Mucoadhesive hybrid polymer/liposome paste is a new drug delivery system presenting controllable and tailorable delivery mechanism. By using mucoadhesive material, the delivery can be more specific and local. Here, we present a study investigating the effect of polymer type, concentration, functional end group, and cross-linking on the release profile of nanoliposomes from polymer pastes. Polymer pastes can be expected to combine the mucoadhesion mechanisms of dry and wet dosage forms but have not been studied extensively. To better understand the mucoadhesion of pastes, we investigated a series of pastes based on the same polymer and used different chemical modifications that can produce interactions at different levels. Native and thiolated polymers presented enhanced mucoadhesion in a wet environment in comparison to acrylated polymers which dissolved rapidly because of the enhanced solubility of PEG chains in water. Paste cross-linking resulted in a sustained release profile compared to non-cross-linked pastes. Pectin-SH pastes, especially 3% (w/v), showed a linear liposomal release profile which is ascribed to the combination of ionic cross-linking and disulfide bridging. By configuring the polymer type or concentration, we can control the release mechanisms and achieve distinct inherent properties which can be applied for diverse medical applications.

Mucoadhesive alginate pastes with embedded liposomes for local oral drug delivery.

Oral cancers are extremely common among adults with increasing incidences due to human papillomavirus, while treatment modalities are limited. This study aims to develop a new oral mucoadhesive delivery system based on the combination of alginate and liposomes. The polymer provides adhesion properties and induces local release of the drug-loaded carriers, while the liposomes protect the drug from degradation and improve its absorption into the cells. Three hybrid alginate/liposomes delivery systems were investigated: a hybrid paste, which presented excellent adhesive capabilities, yet fast burst release of 90% after 2h; a hybrid hydrogel, demonstrating controllable release rates of 5%, 30% or 60% after 2h but poor mucoadhesive properties. These findings led to the development of a hybrid cross-linked paste. Polymer retention studies demonstrated that 80% of the crosslinked paste was retained on tongue tissue compared to 50% retention of the non-cross-linked pastes, verifying its superior mucoadhesion. The hybrid cross-linked paste presented controllable release rate of 20% after 2h. Alginate paste incorporating doxorubicin loaded liposomes presented similar release rates and were highly effective in promoting cancer cell death. Thus, our innovative formulation, including both desired characteristics of mucoadhesion and sustained liposomes release, is an important milestone in the development of a new potential treatment for oral cancer.

Acrylated Chitosan Nanoparticles with Enhanced Mucoadhesion.

The aim of this study was to investigate the effect of acrylate modification on the mucoadhesion of chitosan at the nanoscale. Nanoparticles were fabricated from acrylated chitosan (ACS) via ionic gelation with tripolyphosphate and were characterized in terms of size, zeta potential, stability, and nanoparticle yield. Chitosan (CS) nanoparticles, serving as a control, were fabricated using the same procedure. The mucoadhesion of the nanoparticles was evaluated using the flow-through method after different incubation periods. The retention percentages of ACS nanoparticles were found to be significantly higher than those of CS nanoparticles, for all studied time intervals. An additional indication for the increased mucoadhesion of ACS nanoparticles was the increase in particle size obtained from the mucin particle method, in which mucin and nanoparticles are mixed at different ratios. NMR data verified the presence of free acrylate groups on the ACS nanoparticles. Thus, the improved mucoadhesion could be due to a Michael-type addition reaction between the nanoparticles and thiol groups present in mucin glycoprotein, in addition to entanglements and hydrogen bonding. Overall, ACS nanoparticles exhibit enhanced mucoadhesion properties as compared to CS nanoparticles and could be used as vehicles for drug delivery systems.

Alginate modified with maleimide-terminated PEG as drug carriers with enhanced mucoadhesion.

The goal of this study was to generate a new mucoadhesive carbohydrate-based delivery system composed of alginate (Alg) backbone covalently attached to polyethylene glycol (PEG) modified with a unique functional end-group (maleimide). The immobilization of PEG-maleimide chains significantly improved the mucoadhesion properties attributed to thioether bonds creation via Michael-type addition and hydrogen bonding with the mucus glycoproteins. Mucoadhesion studies using tensile and rotating cylinder assays revealed a 3.6-fold enhanced detachment force and a 2.8-fold enhanced retention time compared to the unmodified polymer, respectively. Additional indirect studies confirmed the presence of polymer-mucus glycoproteins interactions. Drug release experiments were used to evaluate the release profiles from Alg-PEG-maleimide tablets in comparison to Alg and Alg-SH tablets. Viability studies of normal human dermal fibroblasts cells depicted the non-toxic nature of Alg-PEG-maleimide. Overall, our studies disclose that PEG-maleimide substitutions on other biocompatible polymers can lead to the development of useful biomaterials for diverse biomedical applications.

Curcumin Protects Skin against UVB-Induced Cytotoxicity via the Keap1-Nrf2 Pathway: The Use of a Microemulsion Delivery System.

Curcumin was found to be beneficial in treating several skin pathologies and diseases, providing antioxidant protection due to its reducing properties and its electrophilic properties (the ability to activate the Nrf2 pathway and induce phase II cytoprotective enzymes). Nevertheless, clinical applications of curcumin are being hampered by its insufficient solubility, chemical instability, and poor absorption, leading to low efficacy in preventing skin pathologies. These limitations can be overcome by using a nanotechnology-based delivery system. Here, we elucidated the possibility of using curcumin encapsulated in a microemulsion preserving its unique chemical structure. We also examined whether curcumin microemulsion would reduce UVB-induced toxicity in skin. A significant curcumin concentration was found in the human skin dermis following topical application of a curcumin microemulsion. Moreover, curcumin microemulsion enhanced the reduction of UV-induced cytotoxicity in epidermal cells, paving the way for other incorporated electrophiles in encapsulated form protecting skin against stress-related diseases.

Pectin-chitosan physical hydrogels as potential drug delivery vehicles.

Pectin-chitosan hydrogels are intriguing and relatively new type of physically crosslinked hydrogels. Here we present for the first time a study exploring the suitability of pectin-chitosan hydrogels to serve as drug carriers and the mechanism controlling the release patterns. Using drug release assays, we demonstrated sustained release of three model drugs (mesalamine, curcumin and progesterone) over a period of 24h in physiological conditions. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) experiments were used to characterize the interactions between the investigated drugs and the polymers. These experiments, as well as swelling analysis, support the claim that the magnitude of interactions strongly affect the release rates. These new pectin-chitosan thermoreversible hydrogels may improve the life style of many patients by reducing the daily uptake of chronic medicines.

A novel role of topical iodine in skin: Activation of the Nrf2 pathway.

For a long time iodine has been used as an active dermal agent in the treatment of inflammatory, immune-mediated and infectious diseases. Moreover, topical iodine application has been reported to provide protection against sulfur-mustard-induced skin lesions, heat-induced and acid-induced skin burns in both haired guinea-pigs and mouse ear swelling models. However, the exact mechanism of action underlying these benefits of iodine has not yet been elucidated. In the current study, a novel mechanism of action by which iodine provides skin protection and relief, based on its electrophilic nature, is suggested. This study demonstrates that both iodine and iodide are capable of activating the Nrf2 pathway in human skin. As a result, skin protection against UVB-induced damage was acquired and the secretion of pro-inflammatory cytokines (IL-6, IL-8) from LPS-challenged skin was reduced. Iodide role in the enhanced activation of this pathway is demonstrated. The mode of action by which iodine and iodide activate the Nrf2 pathway is discussed.

Acrylated chitosan for mucoadhesive drug delivery systems.

A new mucoadhesive polymer was synthesized by conjugating chitosan to poly(ethylene glycol)diacrylate (PEGDA) via the Michael type reaction. The product was characterized using NMR. Higher PEGDA grafting efficacy was observed with low molecular weight PEGDA (0.7kDa), compared to long 10kDa PEGDA. The acrylation percentage was calculated based on the reaction of ninhydrin with chitosan, and supported the qualitative NMR findings. The adhesive properties were studied by tensile test and rotating system involving detachment of polymer tablets from a fresh intestine sample. Chitosan modified with high molecular weight PEGDA presented improvement in mucoadhesive properties compared to both non-modified and thiolated chitosan. On the molecular level, rheology measurements of polymer/mucin mixtures provided additional evidence of strong interaction between modified chitosan and mucin glycoproteins. This new polymer shows promise as a useful polymeric carrier matrix for delivery systems, which could provide prolonged residence time of the vehicle on the mucosa surface.

PEGDA hydrogels as a replacement for animal tissues in mucoadhesion testing.

Utilization of animal parts in ex-vivo mucoadhesion assays is a common approach that presents many difficulties due to animal rights issues and large variance between animals. This study examines the suitability of two PEGDA (poly(ethylene glycol) diacrylate) based hydrogels to serve as tissue mimetics for mucoadhesion evaluation. One hydrogel, termed PEGDA-QT, was composed of pentaerythritol tetrakis (3-mercaptopropionate) and PEG and contained free thiol groups mimicking those found in natural mucosa. The other hydrogel was formed by UV (ultraviolet) curing of PEGDA and mimicked the mechanical property of mucosa but not its chemical constitute. When ranking different first generation mucoadhesive polymers using a tensile assay, both hydrogels showed good agreement with the ranking achieved for porcine small intestine. However, only PEGDA-QT and porcine small intestine shared a similar displacement curve. The same ranking for PEGDA-QT and porcine small intestine was also observed when comparing a second-generation mucoadhesive polymer, thiolated alginate, to native alginate. Our findings suggest that PEGDA-QT could serve as a replacement for porcine small intestine in both mucoadhesion evaluations using a tensile machine and the flow-through method for first and second-generation mucoadhesive polymers.

Composite chitosan hydrogels for extended release of hydrophobic drugs.

A composite chitosan hydrogel durable in physiological conditions intended for sustained release of hydrophobic drugs was investigated. The design is based on chitosan crosslinked with genipin with embedded biocompatible non-ionic microemulsion (ME). A prolonged release period of 48 h in water, and of 24h in phosphate buffer saline (PBS) of pH 7.4 was demonstrated for Nile red and curcumin. The differences in release patterns in water and PBS were attributed to distinct dissimilarities in the swelling behaviors; in water, the hydrogels swell enormously, while in PBS they expel water and shrink. The release mechanism dominating this system is complex due to intermolecular bonding between the oil droplets and the polymeric network, as confirmed by Fourier transform infrared spectroscopy (FTIR) experiments. This is the first time that oil in water microemulsions were introduced into a chitosan hydrogels for the creation of a hydrophobic drug delivery system.

Mucoadhesive acrylated block copolymers micelles for the delivery of hydrophobic drugs.

Blockpolymer micelles having acrylated end groups were fabricated for the development of mucoadhesive drug loaded vehicle. The critical micelle concentration (CMC) of Pluronic(®) F127 modified with acrylate end groups (F127DA) was found to be similar to that of the unmodified Pluronic(®) F127 (F127). Small angle X-ray scattering verified existence of micelles with an inner core of 4.9±0.2 and 5.5±0.3 for F127 and F127DA respectively. Indomethacin, a hydrophobic drug, was incorporated into the micelles using the thin-film hydration method. In vitro drug release assay demonstrated that the micelles sustained the release of the drug in comparison with free drug in solution. Several methods were used for mucoadhesion evaluation. Viscosity profiling was performed by shear rate sweep experiment of hydrated commercial mucin, F127 or F127DA, and combination of both mucin and a copolymer. Elevated viscosity was achieved for acrylated micelles with mucin compared to mixtures of non-acrylated micelles with mucin. The mucoadhesivity of the acrylated micelles was further characterized using nuclear magnetic resonance (NMR); data affirmed the Michael type addition reaction occurred between acrylates on the micelles corona and thiols present in the mucin. SAXS scattering data further showed a modification in the scattering of F127DA micelles with the addition of pig gastric mucin. Cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) data detected increase in the aggregates size while using acrylated micelles enhance mucoadhesion. Thus acrylated F127DA micelles were found to be mucoadhesive, and a suitable and preferred candidate for micellar drug delivery to mucosal surfaces.

A modified emulsion gelation technique to improve buoyancy of hydrogel tablets for floating drug delivery systems.

The use of buoyant or floating hydrogel tablets is of particular interest in the sustained release of drugs to the stomach. They have an ability to slow the release rates of drugs by prolonging their absorption window in the upper part of the gastrointestinal (GI) tract. In this study we synthesized bioactive hydrogels that have sustainable release rates for drugs in the stomach based on a hydrogel preparation technique that employs emulsifying surfactants. The emulsion gelation technique, which encapsulates oil droplets within the hydrogels during crosslinking, was used to decrease their specific gravity in aqueous environments, resulting in floating drug release depots. Properties such as swelling, buoyancy, density and drug release were manipulated by changing the polymer concentrations, surfactant percentages and the oil:polymer ratios. The relationship between these properties and the hydrogel's floating lag time was documented. The potential for this material to be used as a floating drug delivery system was demonstrated.

Designing a biocompatible hydrogel for the delivery of mesalamine.

A new design for nanocomposite hydrogels based on cross-linked chitosan for the delivery of mesalamine is presented. To enhance drug loading in chitosan, the mineral montmorillonite was incorporated into the matrix. The exfoliated silica montmorillonite nanosheets form interactions with both chitosan and mesalamine, which affect the hydrogel's drug release mechanism and swelling properties. The impact of montmorillonite and glutaraldehyde concentrations on the hydrogel properties was investigated. In vitro drug-release studies detected slower release over short times when montmorillonite was introduced into the matrix. This study is the first to evaluate the influence of pH during mixing and on mixing duration. It was shown that lowering the pH during mixing delayed the release since the positively charged drug was better introduced between the montmorillonite layers, as confirmed by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) analysis. All hydrogels showed prolonged sustained release of mesalamine over 24h in simulated colonic fluid (pH 7.4). When modeled, the mesalamine release profile suggests a complex release mechanism, involving adsorption of the drug to the montmorillonite and its diffusion. The results imply that chitosan-montmorillonite hydrogels can serve as potential drug carriers for controlled-release applications.