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In this study, oxiconazole nitrate (OXI)-loaded antifungal thermosensitive chitosan/carboxymethylcellulose/scleroglucan/montmorillonite (CHT/CMC/SGL/MMT) nanocomposite hydrogels were developed for onychomycosis treatment. The presence of 5% (w/w) MMT within hydrogel matrix increased the glass transition temperature of CHT/CMC/SGL material from 63.72 °C to 76.75 °C and the compressive stress value from 126.45 ± 8.83 kPa to 266.99 ± 6.60 kPa. For the use of hydrogel materials in the treatment of onychomycosis, antifungal OXI drug was loaded into the network of thermosensitive CHT/CMC/SGL and CHT/CMC/SGL/MMT hydrogels and the release of OXI from these materials was monitored spectrophotometrically. At the end of 420 min, for hydrogel systems containing 0, 1, 3 and 5 % (w/w) MMT, OXI release amounts were determined as 70.33 ± 1.74 %, 63.92 ± 0.31 %, 58.78 ± 1.45 % and 52.89 ± 0.21 %, respectively. This means that the drug release depends on the MMT amount within hydrogel matrix and can be controlled by changing the amount of clay mineral in hydrogel material. OXI-loaded new hydrogels showed high antifungal activity against Trichophyton mentagrophytes and Trichophyton rubrum dermatophytes. This study suggests that new antifungal thermosensitive CHT/CMC/SGL/MMT nanocomposite hydrogels could be promising materials for onychomycosis treatment.

In the present study, for the first time, agar/κ-carrageenan and agar/κ-carrageenan/montmorillonite hydrogel materials were prepared by the free-radical crosslinking reaction of agar and κ-carrageenan in the presence of triethylene glycol divinyl ether (TEGDE) as the crosslinker agent. Here, montmorillonite (MMT) modified with phenylalanine was used as additive agent. Agar/κ-carrageenan hydrogel materials with and without MMT were characterized by FTIR, SEM and XRD analyses. The effect of free radical initiator (ammonium persulfate, APS) concentration, crosslinking agent (TEGDE) concentration, reaction temperature, polysaccharide ratio and MMT concentration on the swelling performance and surface property of hydrogel material was investigated and optimum reaction conditions were determined. Maximum equilibrium swelling capacity of the agar/κ-carrageenan hydrogel was found to be 2523 % under the optimum conditions ([APS] = 5 × 10−4 M, [TEGDE] = 5 × 10−4 M, T = 70 °C and magar:mκ-carrageenan = 1:4). An increase of the MMT content within hyrogel matrix led to a decrease in the swelling values of hydrogels. All of the hydrogels prepared in various formulations exhibited non-Fickian swelling behavior. New hydrogel materials obtained from this study could be potential candidates for biomedical applications.

In this study, gelatin-based conductive hydrogels doped with carbon nanotube (CNT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and silver (Ag) nanoparticle were prepared for use in biopotential measurements. Gelatin was modified by various concentrations of methacrylic anhydride (MA) to obtain photo-crosslinkable gelatin methacrylate (GelMA) polymer with low (21%), medium (44%) and high (78%) methacrylation degree. Chemical modification of gelatin was characterized by 1H-NMR spectroscopy. It was observed that mechanical properties of the GelMA hydrogels were highly dependent on methacrylation degree. Ultimate compressive stress of low, medium and high methacrylated gelatin hydrogel was measured to be 9.97 ± 0.14 kPa, 17.83 ± 1.73 kPa and 38.23 ± 2.96 kPa, respectively. Surface morphology of hydrogels was visualized by scanning electron microscope (SEM). The pore size of methacrylated gelatin hydrogel significantly reduced with the addition of CNT, PEDOT:PSS and Ag nanoparticle into the hydrogel matrix. The results of thermal gravimetric analysis showed that conductive hydrogels were of higher thermal stability than nonconductive GelMA hydrogel. The suitability of the prepared hydrogels for biopotential measurements was determined by equivalent impedance measurements. Impedance values of hydrogel samples were obtained in the frequency range of 20 Hz–500 Hz. The hydrogel materials prepared in this study exhibited high impedance at low frequencies and low impedance at high frequencies. The results of this study showed that the hydrogels produced with Ag nanoparticle are more suitable electrode materials for physiological measurement systems such as electrocardiography (ECG) and electroencephalography (EEG).

The effects of cationic tetradecytrimethylammonium bromide (TDTMABr), anionic sodium tetradecyl sulfonate (NaTDS) and nonionic Brij 30 surfactants on the electrokinetic and rheological properties of Na-bentonite and sepiolite suspensions have been investigated. It has been found from the zeta potential measurements that the negative surface charge of Na-bentonite and sepiolite has become positive in the presence of 7.5 × 10−3 M and 1.0 × 10−3 M TDTMABr, respectively. As the concentration of NaTDS is increased in the suspension, the zeta potential value of Na-bentonite does not change significantly, but that of sepiolite decreases gradually. Na-bentonite–surfactant suspensions show a thixotropic behavior, on the other hand sepiolite–surfactant suspensions display a rheopexic or thixotropic behavior depending on the surfactant concentration. All clay–surfactant suspensions follow a Bingham type flow behavior. The surfactant concentration leads to significant changes in the plastic viscosity (ηpl) values of sepiolite–surfactant suspensions, on the contrary of Na-bentonite–surfactant systems. Some shifts in the peak positions have been observed in the FTIR spectra of samples, which have provided evidence about the interactions between clay particles and surfactant molecules. This study shows that the suspensions having the desired zeta potential and ηpl values and thixotropic or rheopexic behaviors can be obtained using different clay–surfactant mixtures.

The zeta potential and viscosity values of kaolinite suspensions in cationic poly(diallyldimethylammonium chloride) (PDDACl), anionic poly(sodium 4-styrene sulfonate) (PSSS) and nonionic poly(vinyl alcohol) (PVA) solutions have been determined. The zeta potential value of kaolinite increases with the first addition of PDDACl and PVA solutions, on the contrary of PSSS. Kaolinite–water suspensions exhibit a thixotropic or rheopectic behavior depending on clay concentration. However, kaolinite–polymer suspensions display a thixotropic behavior. The flow type of kaolinite–water and kaolinite–polymer suspensions is Bingham, except kaolinite–PVA suspensions including 7.5 × 10−5 and 1.0 × 10−4 M PVA. It has been found from the relative plastic viscosity measurements that PDDACl and PVA are of a significant effect on the plastic viscosity values of kaolinite suspensions, unlike the PSSS. The interactions between kaolinite and polymer molecules have been investigated by FTIR spectroscopy. This study shows that the zeta potential and viscosity values of kaolinite suspensions can be adjusted using different polymers.

The effect of cationic surfactant, hexadecyltrimethylammonium bromide (HDTMABr), on the electrokinetic and rheological properties of sepiolite suspensions was investigated. The zeta potential measurements indicate that the addition of HDTMABr into the sepiolite suspensions causes the change of surface charge of clay particles from negative to positive. The concentration of sepiolite in the suspension affects differently the flow behavior of sepiolite–water suspensions. The sepiolite–water suspensions containing less than 2.0 wt.% of sepiolite show a thixotropic behavior and a hysteresis loop, whereas the suspensions containing more than 2.0 wt.% of sepiolite exhibit a rheopexic behavior and a hysteresis loop. The addition of 5.0 × 10 −4 M cationic surfactant into the clay suspensions containing 3.0 wt.% of sepiolite leads to a transition from rheopexic suspension to thixotropic suspension. The sepiolite–water and sepiolite–HDTMABr suspensions exhibit a Bingham type flow behavior. The plastic viscosity ( η pl ) values of suspensions decrease with the increase of temperature from 25 °C to 45 °C. The η pl values of sepiolite suspensions are affected differently depending on the surfactant concentration. It can be concluded from the rheological measurements that the flow behaviors and the η pl values of sepiolite suspensions can be controlled with the sepiolite and HDTMABr concentrations. The interactions between sepiolite and HDTMABr were also investigated by FTIR spectrometer.

In this study, the effect of monoethylene glycol (MEG) and different molecular weight of poly(ethylene glycol) (PEG) solutions (PEG200, PEG400, PEG600, PEG1000, PEG3350 and PEG8000) on the electrokinetic and rheological properties of Na-bentonite suspensions were investigated in the polymer concentration range of 1 × 10 −5 to 1 × 10 −1 M. The physicochemical properties of Na-bentonite such as chemical composition, cation exchange capacity, density, particle size distribution and specific surface area were determined to characterize the clay sample. Na-bentonite did not have an isoelectric point value in the pH ranges of 1.75–11.56 and it had a negative surface charge in studied pH ranges. The zeta potential values of clay–polymer suspensions were less negative at high concentrations (at 1 × 10 −1 M and 1 × 10 −2 M) and at higher molecular weights of polymer in the suspensions. The suspensions exhibited Bingham flow behavior. Some peak position variations were observed in the FTIR spectra of Na-bentonite interacted with PEG molecules when it was compared with purified Na-bentonite and pure polymer spectra.