A sensitive determination of morphine in plasma using AuNPs@UiO-66/PVA hydrogel as an advanced optical scaffold

Bionic artificial penile Tunica albuginea

Polyvinyl Alcohol (PVA) hydrogel microspheres for controlled release of fertilizer (KNO3) and Tribenuron Methyl Herbicide (TBM) were prepared by blending the naturally occurring Alginate (AL) and Pectin (PE). The cross-linking in PVA hydrogel microspheres was carried out by varying the amount of glutaraldehyde from 0.5-1.0 wt%. To control the loading and release properties of PVA hydrogel microspheres, a small amount of NaCl (0.2 wt%) was also added in formulation of microspheres. The blending of PE and AL in PVA hydrogel microspheres was confirmed with FT-IR spectra and by increased thermal stability PVA hydrogel as determined by Differential Scanning Calorimetry (DSC) and Thermogravimetric (TGA) analysis. The PVA hydrogel microspheres were characterized for degree of swelling and for loading and cumulative release of fertilizer (KNO3) and herbicide (TBM), which were carried out in solutions of different pH and at different temperatures. The Scanning Electron Micrographs (SEM) of PVA hydrogel microspheres were recorded before and after the release of loaded agrochemicals and used to confirm the shape and homogeneous blending of PE/AL in PVA hydrogels. The enhanced brittle morphology form SEM images of PVA hydrogel microspheres after the release of loaded agrochemicals has suggested the controlled release of agrochemicals through a mechanism of degradation of polymer chains. Thus natural polymer blended PVA hydrogel microspheres are found to be a potential candidate for the formulation of controlled release systems for the application of agrochemicals in soils and to overcome the environmental problem, which usually encountered on applications of fertilizers and herbicides in agricultural fields by conventional methods.

Simple and highly sensitive determination of morphine in rat plasma by liquid chromatography with fluorescence detection

Infrared-light-driven self-healing MoS2/polyvinyl alcohol hydrogel with simultaneous enhancement of strength and ductility

Polyvinyl alcohol (PVA) hydrogels are well-known biomimetic 3D systems for mammalian cell cultures to mimic native tissues. Recently, several biomolecules were intended for use in PVA hydrogels to improve their biological properties. However, retinol, an important biomolecule, has not been combined with a PVA hydrogel for culturing bone marrow mesenchymal stem (BMMS) cells. Thus, for the first time, the effect of retinol on the physicochemical, antimicrobial, and cell proliferative properties of a PVA hydrogel was investigated. The ability of protein (3.15 nm) and mineral adsorption (4.8 mg/mL) of a PVA hydrogel was improved by 0.5 wt.% retinol. The antimicrobial effect of hydrogel was more significant in S. aureus (39.3 mm) than in E. coli (14.6 mm), and the effect was improved by increasing the retinol concentration. The BMMS cell proliferation was more upregulated in retinol-loaded PVA hydrogel than in the control at 7 days. We demonstrate that the respective in vitro degradation rate of retinol-loaded PVA hydrogels (RPH) (75-78% degradation) may promote both antibacterial and cellular proliferation. Interestingly, the incorporation of retinol did not affect the cell-loading capacity of PVA hydrogel. Accordingly, the fabricated PVA retinol hydrogel proved its compatibility in a stem cell culture and could be a potential biomaterial for tissue regeneration.

Freeze/thawed polyvinyl alcohol hydrogels: Present, past and future

Polyvinyl alcohol (PVA) hydrogels have been widely studied for biomedical applications due to their water solubility, non-toxicity, non-carcinogenicity, and biocompatibility. However, PVA hydrogels prepared by the physical crosslinking method usually do not exhibit a macroporous structure, which limits their application when PVA hydrogels are used alone as a wound dressing. Here, we reported a sponge-like macroporous PVA hydrogel (SPH) prepared by employing polyethylene glycol and nano-hydroxyapatite (n-HA) to enhance phase separation. After being fabricated through cyclic freezing/thawing, the resulting PVA hydrogels possessed macroporous structures. The swelling ratio could reach nearly 1500%, resulting from the excellent water absorption capacity, and the sample could rapidly restore to the original state after being pressed, suggesting a sponge-like characteristic. Furthermore, cell experiments showed that macroporous PVA hydrogels exhibited good biocompatibility and the results of wound closure and H&E analysis consistently indicated that SPHs could significantly promote the wound healing process.

Catheterization procedure is a typical example of minimally invasive medical treatment. This has the advantage that the physical burden on the patient can be remarkably reduced as compared with the conventional medical treatment method involving craniotomy or hemorrhage etc. However, on the other hand, since visual and tactile restrictions are limited at the time of surgery, physicians are required to have expert skill and many experiences. To raise the success rate of surgery irrespective of the amount of surgical experience, we have conducted a simple model using a glass tube and a simulation operation using an experimental animal, but they have low bio-reproducibility and ethical problems was there. In recent years, due to the development of new materials and the appearance of 3D printers, shape reproducibility has improved. A more desirable function of the surgical simulator is to visualize the force applied to the vessel wall surface by the catheter. This is because there is a danger of attracting vascular occlusion etc. when a large force is applied to the wall surface of the blood vessel. Therefore, it is considered important to quantitatively evaluate the operational feeling for simulated surgery. Therefore, we aim to manufacture a vascular surgical simulator with high bio-reproducibility that enables real-time stress measurement. In this research, stress visualization method using photoelastic effect is applied to surgical simulator. By using the photoelastic effect, it becomes possible to check the stress state of the entire field of view, and it is possible to obtain a stress state when a medical instrument such as a coil or a stent is inserted. Therefore, it is useful not only for training but also for the development of medical instruments. Heretofore, examples using PDMS and polyurethane elastomer as a surgical simulator material have been reported, but the longitudinal modulus of elasticity is high and it is unsuitable for a blood vessel model. Therefore, we focused on PVA hydrogel as surgical simulator material. PVA (polyvinyl alcohol) hydrogel is a material that can be expected to reproduce vascular tissue because its physical properties can be easily changed by changing the compounding ratio and degree of polymerization of powdered PVA. By changing the compounding ratio of powdered PVA in the range of 4-15 wt.%, We realized PVA hydrogel's longitudinal elastic modulus of 60-450 kPa. Since the longitudinal elastic modulus of human vascular tissue is 20-3000 kPa, PVA hydrogel is useful for reproducing soft vascular tissue. Further, the average photoelastic coefficient of PVA hydrogel is 2.30 × 10-9 Pa-1, which has a photoelastic coefficient greater than that of polyurethane elastomer which is a photoelastic material useful for photoelastic stress measurement. (photoelastic coefficient of polyurethane elastomer is 1.45 × 10-9 Pa-1.) Therefore, it was confirmed that it is a useful material for stress measurement using photoelastic effect. In this study, a simple blood vessel model was prepared using PVA hydrogel and simulated surgery using a catheter was performed. In addition, a photoelastic observation system was constructed for stress measurement, and a method for correcting the influence due to the presence of incident light, ambient light, and initial stress was examined. As a result, we successfully extracted and visualized the stress applied to the simple blood vessel model.

Polyvinyl alcohol (PVA) hydrogels are extensively used as scaffolds for tissue engineering, although their biodegradation properties have not been optimized yet. To overcome this limitation, partially oxidized PVA has been developed by means of different oxidizing agents, obtaining scaffolds with improved biodegradability. The oxidation reaction also allows tuning the mechanical properties, which are essential for effective use in vivo. In this work, the compressive mechanical behavior of native and partially oxidized PVA hydrogels is investigated, to evaluate the effect of different oxidizing agents, i.e., potassium permanganate, bromine, and iodine. For this purpose, PVA hydrogels are tested by means of indentation tests, also considering the time-dependent mechanical response. Indentation results show that the oxidation reduces the compressive stiffness from about 2.3 N/mm for native PVA to 1.1 ÷ 1.4 N/mm for oxidized PVA. During the consolidation, PVA hydrogels exhibit a force reduction of about 40% and this behavior is unaffected by the oxidizing treatment. A poroviscoelastic constitutive model is developed to describe the time-dependent mechanical response, accounting for the viscoelastic polymer matrix properties and the flow of water molecules within the matrix during long-term compression. This model allows to estimate the long-term Young’s modulus of PVA hydrogels in drained conditions (66 kPa for native PVA and 34–42 kPa for oxidized PVA) and can be exploited to evaluate their performances under compressive stress in vivo, as in the case of cartilage tissue engineering.

Hydrogel with anisotropic properties has promising potentials, while its fabrication is still challenging. In this work, chitosan fiber (CF) was designed to reinforce polyvinyl alcohol (PVA) hydrogel anisotropically. First, CF was pre‐treated in a weak acidic buffer to create rough surface as well as outward‐stretched chitosan chain end segments, and then mixed with PVA in solution. A PVA/CFs composite hydrogel was thereafter prepared by casting the mixture with a pushing force followed by freeze‐thawing cycles. The microstructure of the composite hydrogel was characterized by scanning electron microscopy, optical microscopy and Fourier transform infrared spectroscopy, and its mechanical properties at the directions parallel to and perpendicular to the casting force were measured. Our results indicate that the pre‐treated CF can reinforce the PVA hydrogel effectively, especially along the casting force direction. The tensile strength, breaking elongation and toughness of the composite hydrogel with only 0.2% CFs at the parallel direction reach 175%, 117% and 244% those of the PVA hydrogel, respectively. The anisotropic reinforcement effect has been understood by the orientating of CFs and the interfacial bonding between the CFs and the PVA matrix. Moreover, bovine serum albumin was released sustainably from the anisotropic hydrogel to indicate its potential application.

The introduction of nanomaterials to hydrogels is an effective way to improve the mechanical properties of hydrogels. Herein, carbon nanodot (C‐dot) as a new‐found excellent nanomaterial is first added to polyvinyl alcohol (PVA) hydrogel to prepare PVA/C‐dot hydrogel by freeze–thaw method. The appropriate size and plenty of surface functional groups make C‐dot an ideal nucleating agent for PVA crystallization, which leads to form a denser and more uniform cross‐linked network in PVA hydrogel, and in turn enhance the mechanical properties of PVA hydrogel. Compared to pure PVA hydrogel, about a 46.4% increase of tensile strength and 18.5% increase of elongation at break are achieved when the content of C‐dot in PVA/C‐dot hydrogel is 2 wt%, suggesting that C‐dot can effectively improve the mechanical properties of PVA hydrogel. Besides, C‐dot can endow PVA hydrogel with some new properties, such as fluorescence and reducibility. Herein, Ag nanoparticles are simply introduced and uniformly dispersed in PVA hydrogels with the help of reducibility of C‐dot, which can greatly enhance the antibacterial activity of PVA/C‐dot hydrogels, and enlarge their application potential in medical field.image

Although polyvinyl alcohol (PVA) hydrogels display huge potential in tissue engineering, flexible and wearable electronic devices and soft robotics, their low intrinsic thermal conductivity and weak mechanical properties severely limit their wider applications in these areas. Herein, a Hofmeister effect-assisted “directional freezing-stretching” tactic is employed for simultaneously enhancing the intrinsic thermal conduction and mechanical properties of PVA hydrogels. The hydrogels are obtained through directional freezing followed by salting-out treatment and subsequent mechanical stretching and salting-out (DFS). The DFS PVA hydrogel with 15 wt% of PVA and a stretching ratio of 4 (DFS4) exhibits the highest thermal conductivity of 1.25 W/(m·K), which is 2.4 and 2.8 times that of PVA hydrogel prepared through frozen-thawed (FT) [0.52 W/(m·K)] and frozen-salted out (FS) [0.45 W/(m·K)] methods, respectively. The DFS4 PVA hydrogel also possesses greatly improved mechanical performances, exhibiting an elongation at break of 163.1%. In addition, the tensile strength, toughness, and elastic modulus of DFS4 PVA hydrogel significantly increase to 27.1 MPa, 25.3 MJ·m-3, and 21.5 MPa from 0.4 MPa, 0.32 MJ·m-3, and 0.07 MPa for FT PVA hydrogels, respectively. It is elucidated that the salting-out effect generates hydrophobic and crystalline regions, while directional freezing and stretching enhance the chain orientation in the DFS strategy. These effects synergistically contribute to the improvement of thermal conductivity and mechanical properties of PVA hydrogels.

We previously reported that carbopol hydrogels incorporating indomethacin nanoparticles (IMC NPs) improved the low permeability and bioavailability of skin formulations in transdermal drug delivery systems. However, the combination of NPs with other types of hydrogels has not been sufficiently explored to date. Therefore, this study investigated propylene glycol (PG)/polyvinyl alcohol (PVA) hydrogel as an alternative base to carbopol hydrogel for incorporating IMC NPs. IMC NPs were prepared using bead milling treatment, and these NPs were incorporated into PG/PVA hydrogel (IMC-NP@PG/PVA hydrogel). The IMC concentration was measured using the HPLC method, and seven-week-old Wistar rats were used to evaluate skin absorption. Bead milling reduced the IMC particle size in the PG/PVA hydrogels to the nanoscale (30-200 nm) without altering its crystalline form. The IMC-NP@PG/PVA hydrogel exhibited enhanced uniformity, solubility, and drug release compared to the IMC microparticle-loaded PG/PVA hydrogel (IMC-MP@PG/PVA hydrogel), with a 1.44-fold greater area under the concentration-time curve. Transdermal permeability studies revealed that IMC-NP@PG/PVA had 2.36-fold higher absorption than the IMC-MP@PG/PVA hydrogel, with dissolved IMC permeating the skin. Pharmacokinetics in the rats showed significantly increased plasma levels, absorption rates, and bioavailability for IMC-NP@PG/PVA, demonstrating its superior delivery efficiency. Moreover, the skin absorption of IMC-NP@PG/PVA was higher than that of carbopol hydrogel. These findings highlight the potential of PG/PVA hydrogels as an effective base for transdermal drug delivery systems based on NPs.

Hydrogel wound dressings loaded with PLGA/ciprofloxacin hydrochloride nanoparticles for use on pressure ulcers

Mechanical and kinetic properties of PVA hydrogel immobilizing β-galactosidase