Cell imaging carriers with good biocompatibility have aroused wide attention.[1] Carbon quantum dots (CQDs) have attracted a great deal of attention due to their excellent properties, which is need to capsulated with non-toxic materials because of its biological toxicity.[2, 3] Gelatin has been widely used as a delivery vehicle on account of its good biocompatibility and biodegradability.[4] In this work, fluorescent gelatin nanoparticles (GNPs) were successfully fabricated by simple-cocervation and UV-crosslinking method with carbon quantum dots (CQDs) and fluorescein isothiocyanate (FITC) as fluorescence factors. The morphology and size were characterized by TEM and particle size analyzer. The average diameter of the gelatin nanoparticles (GNPs) is estimated at 390±50 nm. Meantime, the CQDs/GNPs have fluorescent properties with maximum emission at 416nm, with a slight 6±1nm blue-shift compared with CQDs. In vitro cytotoxicity test suggested that CQDs/GNPs and FITC/GNPs had not obvious toxic effect on L929 cells compared to that of individual CQDs and FITC. By confocal microscope observation, CQDs/GNPs and FITC/GNPs could bind to L929 cells for labeling. The results showed that gelatin nanoparticles have excellent fluorescence luminescence performance, including gelatin particles could be an ideal carriers for fluorescence factors. This work provided a new pathway for fabricating gelatin-based carriers for cell labeling and imaging.
Keywords:Gas sensing materials fabricated from graphene based materials have been shown to provide good sensing properties: high surface area providing low limit of detection; facilitating gas interaction owing to the oxygen species functionalized on their structure promoting energy and gas adsorptions [1]. Different types of graphene materials namely; the commercial graphene (cm-G), the commercial graphene oxide (cm-GO), reduced graphene oxide (rGO), and the synthesized graphene oxide (OIHM-GO), and their composites with polyindole (PIn) were used as methanol sensing materials. The synthesized graphene oxide was synthesized by the optimized improved Hummers method because of its non-toxic method, fast preparation and low cost [2]. Herein, the synthesized GO was called OIHM-GO. The reduced graphene oxide was prepared by two different methods, the thermally mild reduction at 120˚C to yield the in situ T-rGO and the chemically reduction by ascorbic acid to yield the in situ C-rGO, in which the cm-GO was used as a raw material.
The different types of graphene materials presented different behavior responses toward methanol. The hydrophilicity of graphene materials related to oxygen content was the key factor for the methanol response.
The sensing responses were evaluated from the relative electrical conductivity at room temperature by a custom-built two point probe.
The element content of materials was clarified by X-ray photoelectron spectroscopy in which GO showed a higher oxygen content than rGO, and G, respectively. The functional groups were also confirmed by Fourier-transform infrared spectroscopy. The morphology was checked by Emission Scanning Electron Microscope.
Among the widely used soft materials, hydrogels have been investigated because of their biocompatibility, water absorption, softness, and flexibility to convert the external stimuli into the mechanical actuation by changing volume through shrinking, swelling or bending [1]. Agarose (AG), a non-ionic linear polysaccharide extracted from red seaweeds, is one of two main components of agar in addition to agaropectin. It has been widely used to study the thermo-reversible gelation. Generally, the gelation mechanism of agarose hydrogel occurs via the hydrogen bonding of helical structure, called physically cross-linked hydrogel [2].
In the present work, the agarose hydrogels (AG HyGels) were fabricated by a solvent casting method. The electromechanical properties, namely the storage modulus (G') and the storage modulus relative response (ΔG'/G'0) under various agarose contents, electric field strengths, and operation temperature were investigated by a rheometer. The electro-induced bending responses, namely the deflection angle and the dielectrophoresis force (Fd) were examined under various agarose contents and electric field strengths by immersing the sample in a silicone oil chamber between two parallel copper electrodes.
In the electromechanical properties under applied electric field strength of 800 V/mm, the highest storage modulus (G') and storage modulus relative response (ΔG'/G'0) of 4.48 x 106 Pa and 1.07 were obtained from the AG HyGel_12.0%v/v due to the electrostriction effect [3]. With increasing operating temperature, the intermolecular hydrogen bonding interaction between the agarose chains were disturbed, leading to the decrease in the G' [4]. For the electro-induced bending response, the free ends of the AG HyGels bended toward the positively charged electrode depending on the electric field strength, implying the attractive interaction between the polarizations of the AG HyGel and the electrode [5]. The highest deflection angle of 74° was obtained from the AG HyGel_2.0%v/v due to its initial lower rigidity.
Comparing the performances with other bio-based hydrogels, the AG HyGels are possible candidates to use as electro-responsive hydrogels for soft actuator applications.
Stimuli responsive polymeric materials are materials that can convert external stimuli such as electric field, heat, light, and magnetic field into mechanical work [1]. They have been utilized in various applications, including medical devices, switches, artificial muscle, and shape memory materials [2]. In recent decades, biopolymers are promising materials to replace the petroleum-based polymers in which poly (lactic acid) (PLA) has attracted a great deal of attention. PLA can respond under applied electric field due to the carbonyl group in main chain that can rotate in the presence of electric field [3].
In this work, the PLA composites consisting of MWCNT as a nanofiller and DBP as a plasticizer were prepared by solvent casting. The electromechanical properties were investigated in the terms of the MWCNT concentration and electric field strength.
The PLA composites showed good recoverability during the time sweep test. The storage modulus response (∆Gꞌ) increases with increasing MWCNT content from 0 to 0.5%v/v and then decreases and become negative values after the MWCNT content higher than 0.8%v/v. 0.1%v/v MWCNT/PLA/DBP composite provided the highest storage modulus sensitivity of 1.56 at the electric filed strength of 1.5 kV/mm. Moreover, the 0.1%v/v MWCNT/PLA/DBP showed higher bending distances and dielectrophoresis forces at the electric filed strength below 300 V/mm.
