Controlled release of antibiotics from photopolymerized hydrogels: Kinetics and microbiological studies

Development of Drug-Loaded PCL@MOF Film Enclosed in a Photo Polymeric Container for Sustained Release

The programmed fabrication of oral dosage forms is associated with several challenges such as controlled loading and disintegration. To optimize the drug payload, excipient breakdown, and site-specific sustained release of hydrophobic drug (sulfamethoxazole, SM), we propose the development of acrylate polymer tablets enclosed with drug-loaded polycaprolactone (PCL) films. The active pharmaceutical ingredient (API) is physisorbed into the porous iron (Fe)-based metal-organic framework (MOF) and later converted to tangible PCL films, which, upon folding, are incorporated into the acrylate polymer matrices (P1/P2/P3). X-ray powder diffraction (XRPD) analysis and scanning electron microscopy (SEM) micrographs confirmed the stability and homogeneous distribution of MOF within the 50 μm thick film. Adsorption-desorption measurements at ambient temperatures confirmed the decrease in the BET surface area of PCL films by 40%, which was ∼3.01 m/g, and pore volume from 30 to 9 nm. The decrease in adsorption and surface parameters could confirm the gradual accessibility of SM molecules once exposed to a degrading environment. Fourier transform infrared (FTIR) analyses of in vitro dissolution confirmed the presence of the drug in the MOF-PCL film-enclosed tablets and concluded the cumulative SM release at pH ∼ 8.2 which followed the order SM@Fe-MOF < P1/P2/P3 < PCL-SM@Fe-MOF < P1/PCL-SM@Fe-MOF < P3/PCL-SM@Fe-MOF. The results of the study indicate that the P3/PCL-SM@Fe-MOF assembly has potential use as a biomedical drug delivery alternative carrier for effective drug loading and stimuli-responsive flexible release to attain high bioavailability.

Reusable antimicrobial antibiotic-free dressings obtained by photopolymerization

In recent years significant efforts have been made to develop new materials for wound dressing with improved healing properties. However, the synthesis methods usually employed to this end are often complex or require several steps. We describe here the synthesis and characterization of antimicrobial reusable dermatological wound dressings based on N-isopropylacrylamide co-polymerized with [2-(Methacryloyloxy) ethyl] trimethylammonium chloride hydrogels (NIPAM-co-METAC). The dressings were obtained with a very efficient single-step synthesis procedure based on visible light (455 nm) by photopolymerization. To this end, F8BT nanoparticles of the conjugated polymer (poly(9,9-dioctylfluorene-alt-benzothiadiazole) - F8BT) were used as macro-photoinitiators, and a modified silsesquioxane was employed as crosslinker. Dressings obtained by this simple and gentle method show antimicrobial and wound healing properties, without the incorporation of antibiotics or any other additives. The physical and mechanical properties of these hydrogel-based dressings were evaluated, as well as their microbiological properties, through in vitro experiments. Results show that dressings with a molar ratio of METAC of 0.5 or higher exhibit high swelling capacity, appropriate water vapor transmission rate values, stability and thermal response, high ductility and adhesiveness. In addition, biological tests showed that the dressings have significant antimicrobial capacity. The best inactivation performance was found for hydrogels synthesized with the highest METAC content. The dressings were tested several times with fresh bacterial cultures, showing a bacterial kill efficiency of 99.99 % even after three repetitions in a row, employing the same dressing, demonstrating the intrinsic bactericidal property of the materials and their reusability. In addition, the gels show low hemolytic effect, high dermal biocompatibility and noticeable wound healing effects. Overall results demonstrate that some specific hydrogel formulations have potential application as dermatological dressings for wound healing and disinfection.

Advances in Stimuli-responsive Hydrogels for Tissue Engineering and Regenerative Medicine Applications: A Review Towards Improving Structural Design for 3D Printing

The physicochemical properties of polymeric hydrogels render them attractive for the development of 3D printed prototypes for tissue engineering in regenerative medicine. Significant effort has been made to design hydrogels with desirable attributes that facilitate 3D printability. In addition, there is significant interest in exploring stimuli-responsive hydrogels to support automated 3D printing into more structurally organised prototypes such as customizable bio-scaffolds for regenerative medicine applications. Synthesizing stimuli-responsive hydrogels is dependent on the type of design and modulation of various polymeric materials to open novel opportunities for applications in biomedicine and bio-engineering. In this review, the salient advances made in the design of stimuli-responsive polymeric hydrogels for 3D printing in tissue engineering are discussed with a specific focus on the different methods of manipulation to develop 3D printed stimuli-responsive polymeric hydrogels. Polymeric functionalisation, nano-enabling and crosslinking are amongst the most common manipulative attributes that affect the assembly and structure of 3D printed bio-scaffolds and their stimuli- responsiveness. The review also provides a concise incursion into the various applications of stimuli to enhance the automated production of structurally organized 3D printed medical prototypes.

In Situ Forming Hydrogel as a Tracer and Degradable Lacrimal Plug for Dry Eye Treatment

Lacrimal plug is an effective and widely therapeutic strategy to treat dry eye. However, almost all commercialized plugs are fixed in a certain design and associated with many complications, such as spontaneous plug extrusion, epiphora, and granuloma and cannot be traced in the long-term. Herein, a simple in situ forming hydrogel is developed as a tracer and degradable lacrimal plug to achieve the best match with the irregular lacrimal passages. In this strategy, methacrylate-modified silk fibroin (SFMA) is served as a network, and a self-assembled indocyanine green fluorescence tracer nanoparticle (FTN) is embedded as an indicator to develop the hydrogel plug using visible photo-crosslinking. This SFMA/FTN hydrogel plug has excellent biocompatibility and biodegradability, which can be noninvasively monitored by near-infrared light. In vivo tests based on dry eye rabbits show that the SFMA/FTN hydrogel plug can completely block the lacrimal passages and greatly improve the various clinical indicators of dry eye. These results demonstrate that the SFMA/FTN hydrogel is suitable as an injectable and degradable lacrimal plug with a long-term tracking function. The work offers a new approach to the development of absorbable plugs for the treatment of dry eye.

Photo-Crosslinkable Hydrogels for 3D Bioprinting in the Repair of Osteochondral Defects: A Review of Present Applications and Future Perspectives

An osteochondral defect is a common and frequent disease in orthopedics and treatment effects are not good, which can be harmful to patients. Hydrogels have been applied in the repair of cartilage defects. Many studies have reported that hydrogels can effectively repair osteochondral defects through loaded cells or non-loaded cells. As a new type of hydrogel, photo-crosslinked hydrogel has been widely applied in more and more fields. Meanwhile, 3D bioprinting serves as an attractive platform to fabricate customized tissue-engineered substitutes from biomaterials and cells for the repair or replacement of injured tissues and organs. Although photo-crosslinkable hydrogel-based 3D bioprinting has some advantages for repairing bone cartilage defects, it also has some disadvantages. Our aim of this paper is to review the current status and prospect of photo-crosslinkable hydrogel-based 3D bioprinting for repairing osteochondral defects.

Preparation and characterization of starch-cellulose interpenetrating network hydrogels based on sequential Diels-Alder click reaction and photopolymerization

Herein, starch-cellulose interpenetrating network (IPN) hydrogels were fabricated by sequential Diels-Alder click reaction and photopolymerization in water. Moreover, β-cyclodextrin, a commonly used host molecule in supramolecular chemistry, was also introduced to improve the performance of the IPN hydrogel. Firstly, the starch-based dienes were synthesized by modifying starch with N-maleoyl-β-alanine, and the cellulose-based dienophiles were obtained by the reaction of cellulose and furfurylamide succinate; Secondly, the as-synthesized starch-based dienes, cellulose-based dienophiles, polymerizable β-cyclodextrin, crosslinker, and acrylamide were dissolved in water and obtained a transparent solution. The solution was maintained in a water bath of 50 °C for 3 h, forming the first network via catalyst-free click Diels-Alder reaction, subsequently, the second network was formed by photopolymerization. Their preparation conditions were optimized via one-factor experiments and their properties and structures were characterized. Finally, 5- fluorouracil (5-Fu) was used as a model drug to study the sustained release behavior of the drug-loaded hydrogels. Release profile was found to fit in Ritger-Peppas kinetic model and polymer relaxation and drug diffusion made a valuable contribution to drug release. Taking into account the virtues of easily controllable photopolymerization and catalyst-free Diels-Alder reaction, the strategy described here has a potential application in the preparation of IPN hydrogels.

High-Performance UV-Vis Light Induces Radical Photopolymerization Using Novel 2-Aminobenzothiazole-Based Photosensitizers

The popularity of using the photopolymerization reactions in various areas of science and technique is constantly gaining importance. Light-induced photopolymerization is the basic process for the production of various polymeric materials. The key role in the polymerization reaction is the photoinitiator. The huge demand for radical and cationic initiators results from the dynamic development of the medical sector, and the optoelectronic, paints, coatings, varnishes and adhesives industries. For this reason, we dealt with the subject of designing new, highly-efficient radical photoinitiators. This paper describes novel photoinitiating systems operating in UV-Vis light for radical polymerization of acrylates. The proposed photoinitiators are composed of squaraine (SQ) as a light absorber and various diphenyliodonium (Iod) salts as co-initiators. The kinetic parameters of radical polymerization of trimethylolpropane triacrylate (TMPTA), such as the degree of double bonds conversion (C%), the rate of photopolymerization (Rp), as well as the photoinitiation index (Ip) were calculated. It was found that 2-aminobenzothiazole derivatives in the presence of iodonium salts effectively initiated the polymerization of TMPTA. The rates of polymerization were at about 2 × 10-2 s-1 and the degree of conversion of acrylate groups from 10% to 36% were observed. The values of the photoinitiating indexes for the most optimal initiator concentration, i.e., 5 × 10-3 M were in the range from 1 × 10-3 s-2 even to above 9 × 10-3 s-2. The photoinitiating efficiency of new radical initiators depends on the concentration and chemical structure of used photoinitiator. The role of squaraine-based photoinitiating systems as effective dyeing photoinitiators for radical polymerization is highlighted in this article.

Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications

These methods describe how to formulate injectable, supramolecular polymer-nanoparticle (PNP) hydrogels for use as biomaterials. PNP hydrogels are composed of two components: hydrophobically modified cellulose as the network polymer and self-assembled core-shell nanoparticles that act as non-covalent cross linkers through dynamic, multivalent interactions. These methods describe both the formation of these self-assembled nanoparticles through nanoprecipitation as well as the formulation and mixing of the two components to form hydrogels with tunable mechanical properties. The use of dynamic light scattering (DLS) and rheology to characterize the quality of the synthesized materials is also detailed. Finally, the utility of these hydrogels for drug delivery, biopharmaceutical stabilization, and cell encapsulation and delivery is demonstrated through in vitro experiments to characterize drug release, thermal stability, and cell settling and viability. Due to its biocompatibility, injectability, and mild gel formation conditions, this hydrogel system is a readily tunable platform suitable for a range of biomedical applications.

Hydrogels as Drug Delivery Systems: A Review of Current Characterization and Evaluation Techniques

Owing to their tunable properties, controllable degradation, and ability to protect labile drugs, hydrogels are increasingly investigated as local drug delivery systems. However, a lack of standardized methodologies used to characterize and evaluate drug release poses significant difficulties when comparing findings from different investigations, preventing an accurate assessment of systems. Here, we review the commonly used analytical techniques for drug detection and quantification from hydrogel delivery systems. The experimental conditions of drug release in saline solutions and their impact are discussed, along with the main mathematical and statistical approaches to characterize drug release profiles. We also review methods to determine drug diffusion coefficients and in vitro and in vivo models used to assess drug release and efficacy with the goal to provide guidelines and harmonized practices when investigating novel hydrogel drug delivery systems.

Mathematical Modelling of Acetaminophen Release in HPC/PAAm Hydrogel: Synthesis and Application

Hydrogels are commonly used as Drug Delivery Systems (DDS) as patches due to its ability to store drug molecules within their structures. The release can be activated under certain stimuli, such as temperature and pH. In this paper, the mathematical modelling of acetaminophen release in hydroxypropyl cellulose with polyacrylamide (HPC/PAAm) is reported. The HPC/PAAm gel was synthesized in proportions of 25/75 wt% and was characterized by FTIR, DSC, optical microscopy, SEM, and TGA, with and without acetaminophen. The release tests were performed for hypothermic, normal, and febrile human body conditions, at 35, 37, and 39°C, respectively, on two release media: water and phosphate buffer solution. In order to describe the release of acetaminophen in HPC/PAAm gel, a genetic programming algorithm was used to accomplish Multigene Symbolic Regression (MSR). Characterization results showed that the drug was crystallized on the surface of the HPC/PAAm gel. Release test results showed that several simultaneous processes occurred in the acetaminophen diffusion phenomenon. A unique mathematical model was obtained by MSR. This model was able to describe the release of acetaminophen in HPC/PAAm gel with high values of R2 and adjusted R2 and to simulate the drug release at times beyond the end of the experiment. High values of R2 and low values of Coefficient of Variation (CV), Root-Mean-Square Error (RMSE), and Mean Absolute Error (MAE) were obtained from the comparison between the simulated and the experimental data. This allows to conclude that the mathematical model is reliable to represent and simulate the acetaminophen release in HPC/PAAm gel at 35, 37, and 39°C.