Search Results (59)

Oleuropein, the principal secoiridoid phenolic compound of olive leaves (Olea europaea L.), is recognized for its broad-spectrum antimicrobial, antibiofilm, antioxidant, and tissue-regenerative properties. However, its effective local therapeutic application remains challenging due to rapid clearance from the site of administration and limited residence time. In this study, an oleuropein-rich aqueous olive leaf extract was incorporated into a thermoresponsive sol–gel delivery system designed for localized application. The formulation was engineered to remain in a low-viscosity sol state at room temperature and to undergo a temperature-triggered sol-to-gel transition near physiological temperature (~33 °C), enabling in situ gel formation. Oleuropein content was quantified using a validated HPLC method, and the formulation was characterized with respect to physicochemical parameters, thermoreversible gelation behavior, particle size distribution, mechanical properties, and spreadability. Biological performance was evaluated through in vitro cytocompatibility (MTT assay), fibroblast migration (scratch assay), and collagen deposition (Sirius Red staining) in L929 fibroblasts, as well as antibiofilm activity against representative Gram-positive and Gram-negative bacterial strains. The developed sol–gel system demonstrated stable physicochemical characteristics, rapid and reversible thermogelation, suitable mechanical and spreading properties, concentration-dependent inhibition of biofilm formation, and acceptable cytocompatibility within the tested concentration range. Notably, the formulation supported fibroblast viability and collagen-associated responses at optimized concentrations. Overall, the results indicate that the proposed thermoresponsive sol–gel formulation represents a promising strategy for the localized delivery of oleuropein-rich olive leaf extract, combining physicochemical stability with dual wound-healing and antibiofilm functionality. Full article

Background/Objectives: The development of stimuli-responsive hydrogels for biomedical uses is an intense field of research. The use of dendritic crosslinkers can enhance the control over the structure and properties of the networks. This work presents a comparative study on the design and evaluation of Pluronic L35 thermogels, incorporating either hydrophobic carbosilane dendrimers (CBS, generations 1 to 3) or hydrophilic dendritic polyglycerols (dPG, 10 k) as crosslinkers. Methods: The thermogels were synthesized via UV-initiated thiol–ene click chemistry. Additionally, they were characterized through swelling studies, mechanical properties, degradation kinetics as well as loading and release studies of the antitumor drug doxorubicin as poorly soluble model cargo. Results: The incorporation of dendritic crosslinkers allowed higher control over the crosslinking process, while the amphiphilic polymer imparted temperature-responsive properties to the resulting networks. Remarkable differences were observed in swelling behavior, mechanical properties and degradation kinetics, depending on the nature of the dendritic crosslinker. Additionally, regarding doxorubicin loading and release in water, CBS hydrogels produced a sustained release over one week, led by network swelling, while dPG hydrogels exhibited a burst release in 4–24 h but were limited by the stronger interaction of DOX with the dPG scaffold. Conclusions: The study provided useful insight for the tailoring of dendritic thermogels for specific biomedical uses such as controlled drug delivery. Full article

This review presents a comprehensive analysis of modern thermosensitive polymer systems for in situ systems (ISSs) which are used for targeted drug delivery in situ. The main classes of polymers used to create “smart” hydrogels that undergo a “sol–gel” phase transition in response to a temperature stimulus in the physiological range are considered. Key representatives of thermosensitive matrices are described in detail: synthetic block copolymers (poloxamers, block copolymers of polylactic-co-polyglycolic acid with polyethyleneglycol, etc.) and natural, modified natural, and semi-synthetic polymers (chitosan, including in combination with β-glycerophosphate, xyloglucan, etc.). This paper systematizes the advantages and disadvantages of various thermosensitive systems and highlights the key risks in their pharmaceutical development, including the influence of the nature and concentration of the active pharmaceutical ingredients and excipients on the rheological properties and phase transition temperature. Particular attention is paid to the difference between thermoreversible and irreversible gel-forming systems. Modern in vitro, ex vivo, and in vivo methods for evaluating critical quality parameters of thermosensitive systems, such as gelation temperature and time, gel strength, mucoadhesive properties, and release kinetics, are discussed. The need to develop standardized and biologically relevant methods to improve the reproducibility and success of preclinical studies is emphasized. The review is intended to help researchers to make informed choices about polymer matrices and optimize compositions for successful pharmaceutical development. Full article

Silica-reinforced chitosan/collagen hydrogels are useful for biomedical applications. In this study, thermosensitive chitosan/collagen hydrogels were prepared with different amounts of rice husk ash-derived silica (RHA-Si). Fourier-transform infrared (FTIR) spectroscopy was used to analyze the chemical structure. Results showed that adding RHA-Si did not change the main chemical groups but caused slight shifts, indicating physical interactions. Micro-Computed Tomography (Micro-CT) revealed that RHA-Si altered the shape and size of the pores in the hydrogel. The pore structure became more spherical at certain RHA-Si levels, but not consistently. Rheological tests showed that increasing RHA-Si made the hydrogel stiffer and reduced the gelation time. However, the hydrogel weakened under high strain due to broken physical bonds. Compression tests indicated that low RHA-Si (1% w/v) improved the hydrogel’s strength during small deformations. In contrast, the hydrogel was less resistant to compression at higher RHA-Si levels (2–3% w/v). In summary, adding RHA-Si can improve the structure and strength of chitosan/collagen hydrogels, but excessive RHA-Si may reduce flexibility. The RHA-Si content should be adjusted to match the intended application of the hydrogel. Full article

Honey has been recognised for centuries for its potential therapeutic properties, and its application in wound healing has gained attention due to its antimicrobial, anti-inflammatory, and regenerative properties. With the rapid increase in multidrug resistance, there is a need for new or alternative approaches to traditional antibiotics. This paper focuses on the physicochemical changes that occur when formulating honey into Pluronic F127 hydrogels. The manual incorporation of honey, irrespective of quality type, presented the amelioration of Pluronic’s capacity to undergo sol–gel transitions, as investigated by parallel plate rheology. This novel finding was attributed to the formation of fractal aggregates via the hydrogen-bonding-induced irreversible aggregation of honey–PF127 micelles, which subsequently dominate the entire hydrogel system to form a gel. The hydrogen bonding of micelles was identified through Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR), Differential Scanning Calorimetry (DSC), and Dynamic Light Scattering (DLS). This is the first known study to provide physicochemical insight into the effects that honey incorporation has on the thermogelation capacity of Pluronic F127 hydrogels for downstream dermal wound applications. Full article

Objectives: Thermo-gelling hydrophilic polymers like PLGA–PEG–PLGA are known as injectable sustained-release depots for biologics, but they face challenges due to the occurrence of severe burst release. This study aimed to develop a strategy to avoid the initial burst release by pre-encapsulating proteins in polysaccharide microparticles through an aqueous–aqueous emulsion mechanism, thereby enhancing therapeutic retention and linear release kinetics. Methods: Five model proteins (G-CSF, GM-CSF, IGF-1, FVIII, BSA) were encapsulated in dextran microparticles, using an organic solvent-free aqueous–aqueous emulsion method. These particles were dispersed in a 23% (w/w) PLGA–PEG–PLGA solution and injected into a 37 °C release buffer to form a gel depot. The in vitro release profiles were quantified using ELISA and MicroBCA assays over 9–42 days. The bioactivity of the proteins was validated using cell proliferation assays (NFS-60, TF-1, MCF-7) and chromogenic kits. The in vivo pharmacokinetics of the FVIII-loaded formulations were evaluated in Sprague–Dawley rats (n = 5/group) over 28 days. Results: Protein-loaded dextran particles retained their structural integrity within the hydrogel and exhibited minimal burst release (≤5% within 30 min vs. >25% for free proteins). Sustained near-linear release profiles were observed for all the proteins, with complete release by day 9 (G-CSF, GM-CSF, BSA) or day 42 (FVIII). Rats administered with the thermal gel with FVIII–dextran particles showed a significantly lower peak plasma concentration (C_max: 88.25 ± 30.21 vs. 132.63 ± 66.67 ng/mL) and prolonged therapeutic coverage (>18 days vs. 15 days) compared to those administered with the thermal gel with the FVIII solution. The bioactivity of the released proteins remained at ≥90% of the native forms. Conclusions: Pre-encapsulation in dextran microparticles effectively mitigates burst release from thermosensitive hydrogels, while preserving protein functionality. Full article

Cardiovascular diseases such as myocardial infarction or limb ischemia are characterized by regression of blood vessels. Local delivery of growth factors (GFs) involved in angiogenesis such as fibroblast blast growth factor-2 (FGF-2) has been shown to trigger collateral neovasculature and might lead to a therapeutic strategy. In vivo, heparin, a sulfated polysaccharide present in abundance in the extracellular matrix (ECM), has been shown to function as a local reservoir for FGF-2 by binding FGF-2 and other morphogens and it plays a role in the evolution of GF gradients. To access injectable biomaterials that can mimic such natural electrostatic interactions between soluble signals and macromolecules and mechanically tunable environments, the backbone of agarose, a thermogelling marine–algae-derived polysaccharide, was modified with sulfate, phosphate, and carboxylic moieties and the interaction and release of FGF-2 from these functionalized hydrogels was assessed by ELISA in vitro and CAM assay in ovo. Our findings show that FGF-2 remains active after release, and FGF-2 release profiles can be influenced by sulfated and phosphorylated agarose, and in turn, promote varied blood vessel formation kinetics. These modified agaroses offer a simple approach to mimicking electrostatic interactions experienced by GFs in the extracellular environment and provide a platform to probe the role of these interactions in the modulation of growth factor activity and may find utility as an injectable gel for promoting angiogenesis and as bioinks in 3D bioprinting. Full article

Cellulose microgel beads fabricated using the dropping technique suffer from structural irregularity and mechanical variability. This limits their translation to biomedical applications that are sensitive to variations in material properties. Ionic salts are often uncontrolled by-products of this technique, despite the known effects of ionic salts on cellulose assembly. In this study, the coagulation behavior of cellulose/salt solutions was explored as a way to combat these challenges. An ionic salt (NaCl) was added to a cellulose solution (cellulose/NaOH/urea) prior to coagulation in a hydrochloric acid bath. Quantification of the bead geometry and characterization of the pore architecture revealed that balancing the introduction of salt with the resultant solution viscosity is more effective at reducing structural variability and diffusion limitations than other pre-gelling techniques like thermal gelation. Three-dimensional visualization of the internal pore structure of neat cellulose, thermo-gel, and salt-gel beads revealed that adding salt to the solution is the most effective way to achieve 3-D structural uniformity throughout the bead. Coupled with nanoindentation, we confirmed that the salt produced during coagulation plays a critical role in mechanical variability, and that adding salt to the solution before dropping into the coagulation bath completely screens this effect, producing uniform microgel beads with reproducible mechanical properties. Full article

In this work, we present basic research on developing thermogel carriers containing high amounts of model antibody immunoglobulin G (IgG) with potential use as injectable molecules. The quantities of IgG loaded into the gel were varied to evaluate the possibility of tuning the dose release. The gel materials were based on blends of thermoresponsive and degradable ABA-type block copolymers composed of poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) or poly(lactide-co-caprolactone)-b-poly(ethylene glycol)-b-(lactide-co-caprolactone) (PLCL–PEG–PLCL). Primarily, the gels with various amounts of IgG were obtained via thermogelation, where the only factor inducing gel formation was the change in temperature. Next, to control the gels’ mechanical properties, degradation rate, and the extent of antibody release, we have tested two approaches. The first one involved the synergistic physical and chemical crosslinking of the copolymers. To achieve this, the hydroxyl groups located at the ends of the PLGA–PEG–PLGA chain were modified into acrylate groups. In this case, the thermogelation was accompanied by chemical crosslinking through the Michael addition reaction. Such an approach increased the dynamic mechanical properties of the gels and simultaneously prolonged their decomposition time. An alternative solution was to suspend crosslinked PEG–polyester nanoparticles loaded with IgG in a PLGA–PEG–PLGA gelling copolymer. We observed that loading IgG into thermogels lowered the gelation temperature (T_GEL) value and increased the storage modulus of the gels, as compared with gels without IgG. The prepared gel materials were able to release the IgG from 8 up to 80 days, depending on the gel formulation and on the amount of loaded IgG. The results revealed that additional, chemical crosslinking of the thermogels and also suspension of particles in the polymer matrix substantially extended the duration of IgG release. With proper matching of the gel composition, environmental conditions, and the type and amount of active substances, antibody-containing thermogels can serve as effective IgG delivery materials. Full article

A combination of Poloxamer 407 (P407) and hydroxypropyl methylcellulose (HPMC) hydrosols is proposed as an in situ thermo-gelling vehicle for the nasal drug delivery of chlorhexidine–silver nanoparticles conjugates (SN-CX). Optimization of the formulation was carried out by applying varying ratios of P407 and HPMC in the presence and absence of SN-CX so that gelation would occur in the temperature range of the nasal cavity (30–34 °C). Mechanisms for the observed gelation phenomena were suggested based on viscosimetry, texture analysis, and dynamic light scattering. Tests were carried out for sprayability, washout time, in vitro drug release, ex vivo permeation, and antimicrobial activity. When applied separately, HPMC was found to lower the P407 gelation temperature (T_g), whereas SN-CX increased it. However, in the presence of HPMC, SN-CX interfered with the P407 micellar organization in a principally contrasting way while leading to an even further decrease in T_g. SN-CX-loaded nasal formulations composed of P407 16% and HPMC 0.1% demonstrated a desired gelation at 31.9 °C, good sprayability (52.95% coverage of the anterior nasal cavity), mucoadhesion for 70 min under simulated nasal clearance, expedient release and permeation, and preserved anti-infective activity against seasonal Influenza virus and beta-coronavirus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and other pathogens. Our findings suggest that the current development could be considered a potential formulation of a protective nasal spray against respiratory infections. Full article

β-1,3-glucans are a kind of natural polysaccharide with immunomodulatory, antitumor, and anti-inflammatory properties. Curdlan, as the simplest linear β-1,3-glucan, possesses a variety of biological activities and thermogelation properties. However, due to the complexity and variability of the conformations of curdlan, the exact structure–activity relationship remains unclear. We prepare a chemically crosslinked curdlan hydrogel with the unique single-helical skeleton (named S gel) in 0.4 wt% NaOH at 40 °C, confirmed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). X-ray diffractometry (XRD) data show that S gel maintains the single-helical crystal structure, and the degree of crystallinity of the S gel is ~24%, which is slightly lower than that of the raw powder (~31%). Scanning electron microscopy (SEM) reveals that S gel has a continuous network structure, with large pores measuring 50–200 μm, which is consistent with its high swelling property. Using the ¹³C high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) method, we determine that most of the single-helical skeleton carbon signals in the swollen S gel are visible, suggesting that the single-helical skeleton of S gel exhibits fascinating mobility at room temperature. Finally, we reveal that the binding of S gel to coagulation Factor G from tachypleus amebocyte lysate increases and saturates at 20 μL tachypleus amebocyte lysate per mg of S gel. Our prepared S gel can avoid the transformation of curdlan conformations and retain the bioactivity of binding to coagulation Factor G, making it a valuable material for use in the food industry and the pharmaceutical field. This work deepens the understanding of the relationship between the single-helical structure and the activity of curdlan, promoting the development and application of β-1,3-glucans. Full article

Dendritic hydrogels based on carbosilane crosslinkers are promising drug delivery systems, as their amphiphilic nature improves the compatibility with poorly water-soluble drugs. In this work, we explored the impact of the complementary polymer on the amphiphilic properties of the dendritic network. Different polymers were selected as precursors, from the highly lipophilic propylene glycol (PPG) to the hydrophilic polyethylene glycol (PEG), including amphiphilic Pluronics L31, L35 and L61. The dithiol polymers reacted with carbosilane crosslinkers through UV-initiated thiol–ene coupling (TEC), and the resultant materials were classified as non-swelling networks (for PPG, PLU_L31 and PLU_L61) and high-swelling hydrogels (for PEG and PLU_L35). The hydrogels exhibited thermo-responsive properties, shrinking at higher temperatures, and exhibited an intriguing drug release pattern due to internal nanostructuring. Furthermore, we fine-tuned the dendritic crosslinker, including hydroxyl and azide pendant groups in the focal point, generating functional networks that can be modified through degradable (ester) and non-degradable (triazol) bonds. Overall, this work highlighted the crucial role of the amphiphilic balance in the design of dendritic hydrogels with thermo-responsive behavior and confirmed their potential as functional networks for biomedical applications. Full article

Radiofrequency ablation (RFA) of cancer induces an anti-tumor immunity, which is insufficient to prevent recurrences. In mice, RFA–intratumoral immunotherapy by granulocyte–macrophage colony-stimulating factor (GM-CSF) and Bacillus Calmette-Guerin resulted in complete metastases regression. Infectious risk in human needs replacement of live vaccines. Intratumoral purified protein derivatives (PPD) have never been tested in digestive cancers, and the safety of intratumoral immunotherapy after RFA has not yet been validated in human models. We investigated the therapeutic efficacy of combined radiofrequency ablation (RFA) and intratumoral immunotherapy (ITI) using an immune-muco-adherent thermogel (IMT) in a mouse model of metastatic colorectal cancer (CRC) and the safety of this approach in a pig model. Intratumoral stability of the immunogel was assessed using magnetic resonance imaging (MRI) and bioluminescent imaging. Seventy-four CT26 tumor-bearing female BALB/c mice were treated with RFA either alone or in combination with intratumoral IMT. Regression of distant metastasis and survival were monitored for 60 days. Six pigs that received liver radiofrequency and intralesional IMT injections were followed for 15 days. Experimental gel embolisms were treated using an intravascular approach. Pertinent rheology of IMT was confirmed in tumors, by the signal stability during 3 days in MRI and 7 days in bioluminescence imaging. In mice, the abscopal effect of RFA–intratumoral immunotherapy resulted in regression of distant lesions completed at day 16 vs. a volume of 350 ± 99.3 mm³ in the RFA group at day 25 and a 10-fold survival rate at 60 days. In pigs, injection of immunogel in the liver RFA area was safe after volume adjustment without clinical, hematological, and liver biology disorder. Flow cytometry showed an early increase in CD3 TCRγδ+T cells at D7 (p < 0.05) and a late decrease in CD29⁺-CD8 T cells at D15 (p < 0.05), reflecting the inflammation status changes. Systemic GM-CSF release was not detectable. Experimental caval and pulmonary thermogel embolisms were treated by percutaneous catheterism and cold serum infusion. RFA–intratumoral immunotherapy as efficient and safe mini-invasive interventional oncology is able to improve ablative treatment of colorectal liver metastases. Full article

Topical treatments for onychomycosis are of interest to those seeking to avoid systemic drug interactions and to improve systemic safety. This work aimed to develop aqueous-based, simple, and cost-effective vehicles that provide high solubility for ciclopirox and enable the delivery of an active through channels created by nail microporation. Following solubility tests, aqueous gels and thermogels based on hydroxypropylmethylcellulose and poloxamer 407, respectively, were loaded with 8% and 16% ciclopirox. Their performance was then compared to the marketed lacquer Micolamina^® in in vitro release tests with artificial membranes and in in vitro permeation tests with human nail clippings with and without poration. Finally, a microbiological assay compared the best gel formulations and the reference product. Little correlation was observed between the in vitro release and the permeation data, and the drug release was highly membrane-dependent. Ciclopirox nail retention in single-dose, porated nails tests was larger than in daily-dosing, non-porated nail conditions. The series of new gel and thermogel vehicles delivered ciclopirox more effectively than Micolamina^® in single-dose, porated nail experiments. The inhibition of Trichophyton rubrum activity was significantly increased with microporated nails when the gel formulations were applied but not with Micolamina^®. Overall, the results suggest that the new vehicles could be successfully combined with nail microporation to improve the drug delivery and efficacy of topical antifungal medication while reducing the dosing frequency, facilitating patients’ adherence. Full article

Donepezil nasal delivery strategies are being continuously investigated for advancing therapy in Alzheimer’s disease. The aim of this study was to develop a chitosan-based, donepezil-loaded thermogelling formulation tailored to meet all the requirements for efficient nose-to-brain delivery. A statistical design of the experiments was implemented for the optimisation of the formulation and/or administration parameters, with regard to formulation viscosity, gelling and spray properties, as well as its targeted nasal deposition within the 3D-printed nasal cavity model. The optimised formulation was further characterised in terms of stability, in vitro release, in vitro biocompatibility and permeability (using Calu-3 cells), ex vivo mucoadhesion (using porcine nasal mucosa), and in vivo irritability (using slug mucosal irritation assay). The applied research design resulted in the development of a sprayable donepezil delivery platform characterised by instant gelation at 34 °C and olfactory deposition reaching a remarkably high 71.8% of the applied dose. The optimised formulation showed prolonged drug release (t_1/2 about 90 min), mucoadhesive behaviour, and reversible permeation enhancement, with a 20-fold increase in adhesion and a 1.5-fold increase in the apparent permeability coefficient in relation to the corresponding donepezil solution. The slug mucosal irritation assay demonstrated an acceptable irritability profile, indicating its potential for safe nasal delivery. It can be concluded that the developed thermogelling formulation showed great promise as an efficient donepezil brain-targeted delivery system. Furthermore, the formulation is worth investigating in vivo for final feasibility confirmation. Full article