Thin Gelatin Films Research Articles

Ultra-sensitive gas pressure and temperature sensor based on self-forming film technique and vernier effect

In this paper, an ultra-sensitive gas pressure and temperature sensor based on vernier effect is presented. It consists of a single mode fiber (SMF) and hollow cylindrical waveguides (HCW). Through the self-forming film technique, a gelatin film is manufactured at the air core of HCW, and the thickness of the gelatin film manufactured by this technique is only 3.16 μm. The vernier spectrum is formed by the superposition of the spectra of the air cavity (AC) and the mixing cavity. The mixing cavity is composed of AC and gelatin cavity (GC). The thin gelatin film makes the optical path difference between the AC and the mixing cavity smaller, which is beneficial to increase the vernier magnification factor. When the gas pressure changes, the gelatin film will deform abnormally. This abnormally deformation squeezes the film, causing the cavity length of the air cavity to become longer. The experimental results show that the sensor exhibits a high gas pressure sensitivity of 788.22 nm/MPa, and the temperature sensitivity is 0.39 nm/℃. The proposed sensor enables simultaneous measurement of gas pressure and temperature. It also processes the advantages of compact size, low cost, and strong mechanical strength, which makes it suitable for aerospace, Biomedical and Natural gas detection.

Gelatin Used as a Transductor in an Optical Hygrometer Based on a Fabry-Perot Interferometer

The quantities that are usually measured are time, pressure, temperature, and relative humidity to mention but a few. The word humidity is used when we are dealing with water vapor which is a gas. The instrument used to measure the humidity is the hygrometer that can be based on electronics, optics, mechanics, chemicals, and others. The measurement of humidity shows its importance in applications such as food processing, meteorological, semiconductor, building and construction, medical, and automotive to mention but a few. This paper shows the adaptation of an optical interferometer, the Fabry-Perot (F-P), to measure the relative humidity. The transductors that have been probed are gelatin-thin films that are inserted between the mirrors of the FP. When water molecules are absorbed (desorbed) by the gelatin film, its refractive index and thickness change giving a movement of the rings in the interference pattern. The calibration plot comprises the ring displacement as a function of the relative humidity.

Stretchable and Electroactive Crosslinked Gelatin for Biodevice and Cell Culture Applications.

Biomimetic substrates that incorporate functionality such as electroactivity and mechanical flexibility, find utility in a variety of biomedical applications. Toward these uses, nature-derived materials such as gelatin offer inherent biocompatibility and sustainable sourcing. However, issues such as high swelling, poor mechanical properties, and lack of stability at biological temperatures limit their use. The enzymatic crosslinking of gelatin via microbial transglutaminase (mTG) yields flexible and robust large area substrates that are stable under physiological conditions. Here, we demonstrate the fabrication and characterization of strong, stretchable, conductive mTG crosslinked gelatin thin films. Incorporation of the conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate in the gel matrix with a bioinspired polydopamine surface coating is used to enable conductivity with enhanced mechanical properties such as extensibility and flexibility, in comparison to plain gelatin or crosslinked gelatin films. The electroconductive substrates are conducive to cell growth, supporting myoblast cell adhesion, viability, and proliferation and could find use in creating active cell culture systems incorporating electrical stimulation. The substrates are responsive to motion such as stretching and bending while being extremely handleable and elastic, making them useful for applications such as electronic skin and flexible bioelectronics. Overall, this work presents facile, yet effective development of bioinspired conductive composites as substrates for bio-integrated devices and functional tissue engineering.

Thin composite coatings based on gelatin with inorganic nanoparticles

A technique for the formation of gelatin thin films and composite coatings with silicon dioxide and zinc oxide nanoparticles by spin coating has been developed. New data of the morphology and structural characteristics of the formed gelatin and nanocomposite films were obtained by atomic force microscopy. The dependences of the roughness parameters of composite coatings on the content of silicon dioxide and zinc oxide nanoparticles in the polymer matrix are presented. It has been shown that the introduction of inorganic nanoparticles into the gelatin structure makes it possible to form nanocomposites with a rough surface. It has been established that the silicon dioxide nanoparticles incorporation leads to hydrophobization of the surface of polymer-inorganic films based on gelatin. Modification with zinc oxide nanoparticles (up to 8 mg per 1 mg of gelatin) improves the wettability of nanocomposite coatings with water.

Rapid sub-micromolar amperometric enzyme biosensing with free substrate access but without nanomaterial signalling support: oxidase-based glucose detection as a proof-of-principle example.

High-sensitivity electrochemical glucose biosensing has so far been possible only through incorporation of nanomaterials into the glucose oxidase-(GOx) containing polymer layer on the detector surface. Here, as a conceptionally novel simplified option, pure gelatin thin films with covalently attached GOx were used to convert platinum (Pt) disk electrodes into rapidly responding amperometric glucose probes with a sub-micromolar limit of detection. The advanced enzymatic tools are easy to make and, as is crucial for a focus on waste minimization, green and sustainable, through restriction of sensor modification to readily available economical materials.

Improved Magnetoelastic (ME) Sensing By Using Gelatin for Salmonella Pick-up from Large Scale Surfaces

ME sensing, as a fast, on-site, and label-free measurement technique, has been studied in the recent decade for the detection of Salmonella. During the development of ME sensors, there has been a dilemma – to increase sensitivity, the size of a ME sensor must be reduced, while in direct surface detection, a reduced sensor size results in a smaller detection area, larger edge effect, and is harder to handle. To solve this problem, in this paper we introduce a novel gelatin assisted ME sensing system. A gelatin solution at a concentration of 0.05 g/ml was prepared and uniformly applied to the sample surface. A thin gelatin film formed after 2 hours of drying and was easily peeled off to remove most of the Salmonella colonies from the surface. With the application of gelatin, the detection area of one ME sensor was improved from 0.2 mm x 1 mm to 30 mm x 30 mm. In our previous study, swabbing, as an inexpensive, easy-to-use, and widely accepted sampling method, has been used to improve the ME biosensing system for quick detection of surface pathogens. Compared with the swab sampling method, not only was the recovery rate of gelatin assisted ME sensing system much higher, but the detection limit can be significantly improved.

Electron microscopy of elemental silver produced by its reprecipitation in glass-like biopolymer film

Elemental silver incorporated into thin glass-like gelatin films by the reprecipitation of elemental silver initially contained in them is studied by the methods of X-ray diffraction analysis and scanning electron microscopy. For the reprecipitation, silver undergoes a redox process by the following scheme: Ag → AgHal → Ag. It is shown that silver particles have a size of 20 to 30 nm in films and 80 to 100 nm when separated from films.

Improved Biodegradable Radiation Cured Polymeric Film Prepared from Chitosan-Gelatin Blend

The mechanical, thermal, swelling, and release properties of chitosan-gelatin (CG) films have been investigated in order to verify the influence of UV and gamma radiation on the stability of the films. Thin films of chitosan and gelatin (1 : 3, w/w) that were radiated with 100 krad of gamma dose showed the best performance and the TS values reached 25, 45, and 49 MPa, respectively, for chitosan, gelatin, and blend. The corresponding highest TS values were 23, 42, and 45 MPa, respectively, for 10 passes of UV radiation. The effect of radiation over gelatin, chitosan, and CG blend caused modification in the arrangement of molecules in the crystal lattice that is significant by XRD analysis. Surfaces of the films were also investigated by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) studies further revealed structural changes of the films. These changes were attributed to understanding the behavior of the irradiated chitosan, gelatin, and CG blend on application of thermal energy using DSC and TGA studies, water uptake of the films in aqueous medium, and soil degradation properties to observe the best possibility for its application.

Fiber-optic protease sensor based on the degradation of thin gelatin films

Despite increasing interest in situ monitoring of proteolytic activity in chronic wound is not possible and information can only be obtained by sampling wound exudate. In this context, we developed an evanescent wave (EW) fiber-optic sensor to quantify protease activity directly in the wound bed. Detection is based on the degradation of thin gelatin films deposited on the fiber core by dip-coating, which serve as a substrate for proteases. After staining with a chlorophyllin copper sodium salt biocompatible dye, EW absorption occurs proportionally to the dye concentration, which is detected by the variation in light transmission intensity. The sensor response varies proportionally to enzymatic activity, showing sensitivity against MMP-2 and MMP-9 down to 2μg/mL and 10μg/mL, respectively. In addition, it is sensitive to film thickness and crosslink density, thus allowing tuning of the sensitivity and lifetime. Designed to be totally biocompatible and low cost, this miniature sensor has potential for use as a point-of-care disposable device in a clinical environment to assist physicians with quantitative information about the wound healing process.

Sol–gel technology and template synthesis in thin gelatin films

Processes of sol–gel technology of template synthesis of 3d-element metal macrocyclic complexes that occurs in thin films of metalhexacyanoferrate(II) gelatin-immobilized matrix implants under their contact with water solutions containing various (N,O,S)-donor atomic and (C=O) containing organic compounds, have been discussed. It was noted that, in a series of cases, sol–gel technology of template synthesis in the given specific conditions allows to realize such metal macrocyclic complexes formation processes that are not typical at the complexing in solutions or solid phase.

The Effect of Drying Temperature on Physical Properties of Thin Gelatin Films

The molecular morphology of thin gelatin films, controlled through the casting temperature, was monitored by wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Gelatin films dried at lower temperatures had a markedly higher crystalline or helical structure with a slightly higher Tg and lower ΔCp compared with hot dried films, which had a more coiled structure. The relationship between molecular morphology and gelatin-water interaction in terms of hydration behavior and water diffusivity was assessed using dynamic vapor sorption (DVS). The sorption capacity increased and the level of hysteresis decreased with increasing the degree of crystallinity. The difference in the aging behavior of the films was explained in terms of the difference between the glass transition and aging temperatures, (Tg – Ta).

Azodyed gelatin films for holographic recording

In this work we present a preparation method of azo-dyed gelatin thin films for holographic recording and their photoinduced changes of optical properties. The non-toxic, commercially available and cheap ingredients were used for film preparation. The films were prepared by mixing azo-dyes with gelatin solution.The photoinduced properties of prepared films were investigated. The photoinduced dichroism and birefringence at 532nm laser radiation were observed. The holographic recording of surface and volume gratings by 532nm wavelength laser radiation were performed and surface relief gratings were studied with AFM. The mass transport direction in azodyed gelatin was studied.

Comparison of mechanical and degradation properties of EG and EGDMA grafted gelatin films

Thin films of gelatin were prepared from gelatin granules in aqueous medium by casting and its mechanical properties like tensile strength (TS), tensile modulus (TM), and elongation at break (Eb %) were studied. Gelatin films were procured with two types of monomers such as 5% ethylene glycol (EG) and 5% ethylene glycol dimethacrylate (EGDMA) to increase the mechanical properties. Five percent of monomer solutions were prepared in MeOH along with 2% photoinitiator; Irgacure-651. Soaking time and UV radiation intensities were optimized with the extent of polymer loading (PL) and the mechanical properties of the cured films. Comparing the properties of EG and EGDMA treated gelatin film, EG showed the best performance. The EG-cured gelatin film with 5 min soaking time showed the highest tensile strength (58.6 MPa) and elongation at break (11.2%). The water uptake was determined for raw film (500.1%), EG grafted gelatin film (375.3%), and EGDMA grafted film (412.9%). The degradation properties in water and soil were determined for the raw and cured gelatin films. It was observed that the raw film degrades more than that of the treated films.

Superior separation performance of ultrathin gelatin films

Ultrathin gelatin films were prepared by filtering gelatin on a porous nanofibrous scaffold and cross-linked by glutaraldehyde. The gelatin thin films were obtained by using a copper hydroxide nanostrand scaffold after removal of the scaffold. At relative high pressure, the rejection properties of these gelatin films became worse due to mechanical fouling. However, the gelatin/carbon nanotube composite thin films prepared on a single-walled carbon nanotube scaffold could sustain a pressure up to 18 bars with more than 90% rejection for 2–3 nm molecules. The carbon nanotube layer dramatically increased the mechanical properties of the gelatin layer. The pressure dynamically controlled the network structure of the gelatin layer. The corresponding separation performances were investigated in detail. The gelatin films could be as thin as 62 nm. These gelatin films can separate 865 Dalton Direct Yellow 50 molecules at a rate of magnitude one to two orders higher than that of commercially available membranes with similar rejections.

Fe(CN)6]4− decorated mesoporous gelatin thin films for colorimetric detection and as sorbents of heavy metal ions

[Fe(CN)6](4-) decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6](4-) ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6](4-) decorated gelatin films into aqueous solutions of metal ions, such as Fe(3+), Cu(2+), Co(2+), Pb(2+) and Cd(2+) (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6](4-) decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6](4-) functionality and other functional groups of gelatin itself, this [Fe(CN)6](4-) decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water.

Modification of Gelatin Films Using Trimethylolpropane Trimethacrylate (TMPTMA) by Photo-Curing

Thin gelatin films were prepared via casting at 70°C. Tensile strength (TS) and elongation at break (Eb%) of the gelatin films were found to be 20 MPa and 8.7% respectively. To improve the mechanical and thermal properties, gelatin films were cured with trimethylolpropane trimethacrylate (TMPTMA) using UV radiation. Monomer concentration, soaking time of gelatin films in the monomer solution and UV radiation intensity were optimized on the basis of mechanical properties of the cured films. The highest TS was found to be 28.8 MPa for 3% monomer solution at 10th pass of UV for 5 min soaking time. Thermal properties, water uptake and water aging properties of the gelatin films were also studied.

Study on the Water-Aging Properties of Gelatin-Glucose and Gelatin-Urea Films: The Effect of Gamma Radiation

Thin gelatin films (about 0.25 mm thickness) were prepared from granular gelatin via casting. The mechanical properties of gelatin films such as tensile strength (TS), elongation at break (Eb%), water uptake and water aging properties were investigated. To improve the water aging properties of gelatin films, gelatin-glucose and gelatin–urea films were prepared. Effect of gamma radiation on the tensile properties, water uptake and water aging properties of gelatin-glucose and gelatin-urea films were also studied. The results of the investigation show that both glucose and urea can improve the water stability of the gelatin films.

Effect of Urea on the Mechanical Properties of Gelatin Films Photocured with 2-Ethylhexyl Acrylate

Thin films of gelatin were prepared by casting. Then the films were photocured and the mechanical properties were studied. The tensile strength of UV cured gelatin films showed about 10% enhancement than that of raw gelatin films. Minor amount of urea (1–5%) was used as additive in aqueous gelatin solution and films were prepared using same technique. Four formulations were prepared in methanol with 2-ethylhexyl acrylate in the presence of photoinitiator (darocur-1664). The films were soaked in the prepared formulations and then cured under UV radiation at different intensities (5–25 passes). Percentage of urea, monomer concentration, soaking time and radiation intensities were optimized with the extent of polymer loading, TS and elongation at break of the photocured film. The films containing 2% urea, cured with 3% EHA for 3 min at 15th UV pass showed the highest mechanical properties. A significant improvement of TS (31%) occurred when EHA (3%) was incorporated.

Growth and osteogenic differentiation of adipose-derived and bone marrow-derived stem cells on chitosan and chitooligosaccharide films

Very low molecular weight chitooligosaccharide (COS, 1.4 kDa) and high molecular weight chitosan (1000 kDa) were comparatively studied in terms of physical and biological characteristics. Thin films of COS, chitosan and gelatin were prepared and crosslinked by dehydrothermal treatment at 140 °C for 24 h. COS film presented more hydrophilic property than chitosan film. Behaviors of rat adipose-derived stem cells (ASCs) and bone marrow-derived stem cells (MSCs) were investigated on COS and chitosan films, comparing to those on gelatin film. The results on cell spreading suggested that both ASCs and MSCs preferred to attach on COS film than chitosan film with 6–7 times larger cell areas. Numbers of both stem cells proliferated on COS film were approximately 3-fold higher than those on chitosan film. In addition, COS film enhanced osteogenic differentiating potential of MSCs, as observed from the alkaline phosphatase activity and calcium deposition. Therefore, in this work, COS was shown to be a more favorable material for the growth and osteogenic differentiation of both ASCs and MSCs, compared to high molecular weight chitosan.

Film formation and surface gelation of gelatin molecules at the water/air interface

This publication presents new results on the formation of ultra-thin films of porcine gelatin molecules at the water/air surface. In a series of experiments we used the pendant-drop and vibrating-capacitor method for measuring dynamic surface tensions and electrostatic surface potentials. The surface shear and surface elongational rheological properties of the adsorbed layers of gelatin molecules were investigated by the torsion pendulum and the oscillating pendant-drop technique. The results of these experiments showed striking adsorption processes of the polypeptide molecules at the pure water surface even in the highly dilute concentration regime. These thin gelatin films exhibit striking viscoelastic properties, which correspond to two-dimensional gel states.