Gels, Volume 5, Issue 3 (September 2019) – 10 articles

The main scope of the present work is to synthesize pH-responsive Engelhard titanium silicate (ETS)-10 phase crystalline pellets through the smart modification of a synthetic process which was previously applied to the preparation of other phases. The original preparative method, which envisages the use of the same initial synthesis as a binder for the preparation of pellets, was modified by adding an appropriate pH indicator to a number of systems subject to this investigation. It should be noted that the modified process was never before used to give access to pH-responsive ETS-10 phase pellets, and it is disclosed here for the first time. The study started from the definition of the best experimental conditions, which were optimized by analyzing the effects of temperature and system composition. The addition of the pH indicator did not alter the physicochemical characteristics and reactivity of the system. The pH-responsive ETS-10 phase crystalline pellets were characterized by an adequate mechanical strength and by a high capability to change color. The latter aspect can be particularly useful when this material is used in catalytic processes whose performance is strictly dependent on the pH value. The amount of gel used, as well as the working temperature, were the main critical parameters to be controlled during the preparation of pH-responsive ETS-10 phase crystalline pellets. The pellets were fully characterized by X-ray diffraction in order to investigate and identify the possible phases, and by using a hardness tester to measure the compressive strength. Finally, toning tests were performed. Full article

Previous studies involving poly N-vinylcaprolactam (PNVCL) and itaconic acid (IA) have synthesised the hydrogels with the presence of a solvent and a crosslinker, producing chemically crosslinked hydrogel systems. In this study, however, temperature sensitive PNVCL was physically crosslinked with a pH-sensitive comonomer IA through ultraviolet (UV) free-radical polymerization, without the presence of a solvent, to produce hydrogels with dual sensitivity. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy indicated successful polymerisation of the hydrogels. The temperature and pH sensitivity of the hydrogels was investigated. The lower critical solution temperature (LCST) of the gels was determined using the UV spectrometry and it was found that the incorporation of IA decreased the LCST. Rheology was conducted to investigate the mechanical and viscoelastic properties of the hydrogels, with results indicating IA that enhances the mechanical properties of the gels. Swelling studies were carried out at ~20 °C and 37 °C in different buffer solutions simulating the gastrointestinal tract (pH 2.2 and pH 6.8). In acidic conditions, the gels showed gradual increase in swelling while remaining structurally intact. While in basic conditions, the gels had a burst in swelling and began to gradually degrade after 30 min. Results were similar for drug release studies. Acetaminophen was incorporated into the hydrogels. Drug dissolution studies were carried out at 37 °C in pH 2.2 and pH 6.8. It was found that <20% of acetaminophen was released from the gels in pH 2.2, whereas the maximum drug released at pH 6.8 was 74%. Cytotoxicity studies also demonstrated the hydrogels to be highly biocompatible. These results indicate that physically crosslinked P(NVCL-IA) gels possess dual pH and temperature sensitive properties, which may be beneficial for biomedical applications such as drug delivery. Full article

Chitosan-based hydrogels are being widely used in biomedical applications due to their eco-friendly, biodegradable, and biocompatible properties, and their ability to mimic the extracellular matrix of many tissues. However, the application of chitosan hydrogels has been limited due to their inherent mechanical weakness. Halloysite nanotubes (HNTs) are naturally occurring aluminosilicate clay minerals and are widely used as a bulk filler to improve the performance characteristics of many polymeric materials. HNTs have also been shown to be a viable nanocontainer able to provide the sustained release of antibiotics, chemicals, and growth factors. This study’s objective was to develop a stable drug delivery chitosan/HNT nanocomposite hydrogel that is biocompatible, biodegradable, and provides sustained drug release. In this study, chitosan/HNTs hydrogels containing undoped or gentamicin-doped HNTs were combined in different wt./wt. ratios and cross-linked with tripolyphosphate. The effects of chitosan and HNTs concentration and combination ratios on the hydrogel surface morphology, degradability, and mechanical properties, as well as its drug release capability, were analyzed. The results clearly showed that the addition of HNTs improved chitosan mechanical properties, but only within a narrow range. The nanocomposite hydrogels provided a sustained pattern of drug release and inhibited bacterial growth, and the live/dead assay showed excellent cytocompatibility. Full article

The relation between the number of magnetic particles and the change in storage modulus induced by a magnetic field was investigated for weak hydrogels containing carbonyl iron, iron oxide, and barium ferrite particles with different diameters in primary particles while maintaining the magnetization of magnetic particles. The change in storage modulus exhibited a power dependency against the number of magnetic particles, which was nearly independent of the magnetic particles. The change in storage modulus was successfully scaled by the reduced number of magnetic particles using the diameter of secondary particles. Microphotographs revealed that iron oxide and barium ferrite particles form aggregations while carbonyl iron particles are well dispersed in carrageenan gels. The diameter of secondary particles determined by a relation between the change in storage modulus and the reduced number of magnetic particles showed similar values with those observed in microphotographs. Full article

In the present article, the commercial value of fish scales (FS), one of the most discarded fish wastes, has been identified by discovering their gelation capability. Fish scales of different physical forms were applied for the removal of dyes (acid red 1 (AR1), acid blue 45 (AB45), and acid yellow 127 (AY127)) from textile dye solution by absorption process. An astounding phenomenon, gelation of the treated solution, was noticed when it was aged for a certain period. The absorption of dye by FS was confirmed and quantified by FT-IR and UV-visible spectroscopy analyses, respectively. Process optimization revealed that pristine FS showed better gelation efficacy compared to pulverized FS. The gelation process was successful only when the dye solution contained acid and salt. As most of the textile effluents contain acids and salts in the discarded dye solution, this gelation process implies an obvious indication of the saving process and chemical cost in textile waste treatment. The jellified wastewater was characterized by exploring the rheological properties. Based on these analyses, potential application areas have been discussed. Full article

This review summarizes work done on triply, or higher, interpenetrating polymer network materials prepared in order to widen the properties of double polymer network hydrogels (DN), doubly interpenetrating polymer networks with enhanced mechanical properties. The review will show that introduction of a third, or fourth, polymeric component in the DNs would further enhance the mechanical properties of the resulting materials, but may also introduce other useful functionalities, including electrical conductivity, low-friction coefficients, and (bio)degradability. Full article

Many people nowadays undergo treatments to improve their aesthetics, often neglecting the general state of health. Aesthetics and appearance have become of prime importance, perhaps correlating with of the advent of social networks and digital photographs. One of the most requested aesthetic treatments for dentists is dental bleaching through the use of whitening gels. Dental bleaching is a treatment which involves an improvement in the chrome of the teeth in a short time, and this treatment appears not invasive for the patients. In-office and at-home bleaching treatments can be found. The purpose of this scientific study is to evaluate all of the advantages and disadvantages of this medical treatment. In this study, were report information and items related to bleaching side effects. Dentists often find themselves in disagreement on this topic. The PICO (Population/Intervention/Comparison/Outcome) question investigated was: Are dental patients who have dental bleaching an increased risk of teeth damage? All of the data in the literature has been collected, and all of the side effects of this treatment were evaluated. 263 studies emerged from initial research; only 14 were screened after screening, as they contained sufficient data to evaluate the side effects of treatment. One certain thing emerged; among the contraindications to the treatment of dental bleaching dentinal hypersensitivity could be cited. In fact, one of the most reported undesirable effects regards this problem. Other studies have evaluated pain, color improvement and duration, or patient satisfaction. Dental bleaching is a treatment that aims to improve the aesthetics of our patients; this is also reflected from a psychological point of view and therefore has effects on general health. However, the whitening treatment is not suitable for everyone and must be carefully evaluated by a specialist. This treatment also entails maintenance by the patient and therefore better compliance to normal oral hygiene procedures. Full article

Gelatin methacryloyl (GelMA) hydrogels have been used in tissue engineering and regenerative medicine because of their biocompatibility, photopatternability, printability, and tunable mechanical and rheological properties. However, low mechanical strength limits their applications in controlled drug release, non-viral gene therapy, and tissue and disease modeling. In this work, a dual crosslinking method for GelMA is introduced. First, photolithography was used to pattern the gels through the crosslinking of methacrylate incorporated amine groups of GelMA. Second, a microbial transglutaminase (mTGase) solution was introduced in order to enzymatically crosslink the photopatterned gels by initiating a chemical reaction between the glutamine and lysine groups of the GelMA hydrogel. The results showed that dual crosslinking improved the stiffness and rheological properties of the hydrogels without affecting cell viability, when compared to single crosslinking with either ultraviolet (UV) exposure or mTGase treatment. Our results also demonstrate that when treated with mTGase, hydrogels show decreased swelling properties and better preservation of photolithographically patterned shapes. Similar effects were observed when three dimensional (3D) printed and photocrosslinked substrates were treated with mTGase. Such dual crosslinking methods can be used to improve the mechanical properties and pattern fidelity of GelMA gels, as well as dynamic control of the stiffness of tissue engineered constructs. Full article