Project description:The collective properties of self-assembled nanoparticles with long-range order bear immense potential for customized electronic materials by design. However, to mitigate the shortcoming of the finite-size distribution of nanoparticles and thus, the inherent energetic disorder within assemblies, atomically precise nanoclusters are the most promising building blocks. We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au32(nBu3P)12Cl8 nanoclusters into micro-crystals. This enables the determination of emergent optoelectronic properties which resulted from long-range order in such assemblies. Compared to the same nanoclusters in glassy, polycrystalline ensembles, we find a 100-fold increase in the electric conductivity and charge carrier mobility as well as additional optical transitions. We show that these effects are due to a vanishing energetic disorder and a drastically reduced activation energy to charge transport in the highly ordered assemblies. This first correlation of structure and electronic properties by comparing glassy and crystalline self-assembled superstructures of atomically precise gold nanoclusters paves the way towards functional materials with novel collective optoelectronic properties.
Project description:Bovine serum albumin-embedded Au nanoclusters (BSA-AuNCs) are thoroughly probed by continuous wave electron paramagnetic resonance (CW-EPR), light-induced EPR (LEPR), and sequences of microscopic investigations performed via high-resolution transmission electron microscopy (HR-TEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray analysis (EDS). To the best of our knowledge, this is the first report analyzing the BSA-AuNCs by CW-EPR/LEPR technique. Besides the presence of Au(0) and Au(I) oxidation states in BSA-AuNCs, the authors observe a significant amount of Au(II), which may result from a disproportionation event occurring within NCs: 2Au(I) → Au(II) + Au(0). Based on the LEPR experiments, and by comparing the behavior of BSA versus BSA-AuNCs under UV light irradiation (at 325 nm) during light off-on-off cycles, any energy and/or charge transfer event occurring between BSA and AuNCs during photoexcitation can be excluded. According to CW-EPR results, the Au nano assemblies within BSA-AuNCs are estimated to contain 6-8 Au units per fluorescent cluster. Direct observation of BSA-AuNCs by STEM and HR-TEM techniques confirms the presence of such diameters of gold nanoclusters in BSA-AuNCs. Moreover, in situ formation and migration of Au nanostructures are observed and evidenced after application of either a focused electron beam from HR-TEM, or an X-ray from EDS experiments.
Project description:A robust, efficient and sensitive quartz crystal microbalance (QCM) for glucose detection has been constructed using Au@bovine serum albumin (Au@BSA) nanoparticles as an active layer. The nanoparticles serve as tandem nanozymes and their stability over natural enzymes enable the sensor to show a wider linear dynamic range between 0.05 and 15 mM, a higher acid-resistance (pH 2.0-8.0) and heat-resistance (35-60 °C) than conventional glucose oxidase (GOx)-based sensors. The sensor has been further applied to measure glucose content in artificial urine directly without dilution, where the recovery of 99.6-105.2% and the relative standard deviations (RSDs) below 0.88% confirm a good reproducibility for the measurement results. In addition, the developed Au@BSA QCM sensor can retain 95% of its initial activity after 40 days of storage. Overall, the Au@BSA sensor shows better comprehensive performance than the commercial sensor strips for urine glucose analysis and provides a promising approach in a more precise and robust manner.
Project description:Protein denaturation is under intensive research, since it leads to neurological disorders of severe consequences. Avoiding denaturation and stabilizing the proteins in their native state is of great importance, especially when proteins are used as drug molecules or vaccines. It is preferred to add pharmaceutical excipients in protein formulations to avoid denaturation and thereby stabilize them. The present study aimed at using bile salts (BSs), a group of well-known drug delivery systems, for stabilization of proteins. Bovine serum albumin (BSA) was taken as the model protein, whose association with two BSs, namely sodium cholate (NaC) and sodium deoxycholate (NaDC), was studied. Denaturation studies on the pre-formed BSA-BS systems were carried out under chemical and physical denaturation conditions. Urea was used as the chemical denaturant and BSA-BS systems were subjected to various temperature conditions to understand the thermal (physical) denaturation. With the denaturation conditions prescribed here, the data obtained is informative on the association of BSA-BS systems to be hydrophobic and this effect of hydrophobicity plays an important role in stabilizing the serum albumin in its native state under both chemical and thermal denaturation.
Project description:BackgroundTo prepare sorafenib-loaded folate-decorated bovine serum nanoparticles (FA-SRF-BSANPs) and investigate their effect on the tumor targeting.MethodsThe nanoparticles were characterized and evaluated by in vivo and in vitro experiments.ResultsSRF-loaded BSA nanoparticles (SRF-BSANPs) was first prepared and modified with folic acid by chemical coupling to obtain FA-SRF-BSANPs. The average particle size, zeta potential, entrapment efficiency, and drug loading of the optimized FA-SRF-BSANPs were 158.00 nm, -16.27 mV, 77.25%, and 7.73%, respectively. The stability test showed that FA-SRF-BSANPs remained stable for more than 1 month at room temperature. The TEM analysis showed that the surface of FA-SRF-BSANPs was nearly spherical. XRD analysis showed that the drug existed in. the nanoparticles in an amorphous state. FA-SRF-BSANPs can promote the intracellular uptake of hepatoma cells (SMMC-7721) with the strongest inhibitory effect compared with SRF-BSANPs and sorafenib solution. Furthermore, the tumor targeting of FA-SRF-BSANPs (Ctumor/Cblood, 0.666 ± 0.053) was significantly higher than those of SRF-BSANPs (Ctumor/Cblood, 0.560 ± 0.083) and sorafenib-solution (Ctumor/Cblood, 0.410 ± 0.038) in nude mice with liver cancer.ConclusionFA-modified albumin nanoparticles are good carriers for delivering SRF to the tumor tissue, which can improve the therapeutic effect and reduce the side effects of the drug.
Project description:Proteins at interfaces are important for protein formulations and in soft materials such as foam. Here, interfacial stability and physicochemical properties are key elements, which drive macroscopic foam properties through structure-property relations. Native and fluorescein isothiocyanate-labeled bovine serum albumin (BSA) were used to modify air-water interfaces as a function of pH. Characterizations were performed with tensiometry and sum-frequency generation (SFG). SFG spectra of O-H stretching vibrations reveal a phase reversal and a pronounced minimum in O-H intensity at pH values of 5.3 and 4.7 for native and labeled BSA, respectively. This minimum is attributed to the interfacial isoelectric point (IEP) and is accompanied by a minimum in surface tension and negligible ζ-potentials in the bulk. Interfacial proteins at pH values close to the IEP can promote macroscopic foam stability and are predominately located in the lamellae between individual gas bubbles as evidenced by confocal fluorescence microscopy. Different from the classical stabilization mechanisms, for example, via the electrostatic disjoining pressure, we propose that the presence of more close-packed BSA, because of negligible net charges, inside the foam lamellae is more effective in reducing foam drainage as compared to a situation with strong repulsive electrostatic interactions.
Project description:Detailed physicochemical and computational investigation are made to explore different aspects of complexation between bovine serum albumin (BSA) and three structurally different surface active ionic liquids (SAILs), 1-dodecyl-3-methylimidazolium chloride, [C12mim][Cl]; 3-(2-(dodecylamino)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [C12Amim][Cl] and 3-methyl-1-dodecyloxy carbonyl methylimidazolium chloride, [C12Emim][Cl]. The interfacial and bulk complexation behavior has been monitored using tensiometry, conductivity, steady-state fluorescence and turbidity measurements. Thermodynamic insights about complexation have been obtained using isothermal titration calorimetry (ITC) measurements whereas molecular docking studies were used to predict the possible binding sites of SAILs on BSA. The information obtained from these studies helped in establishing the formed BSA-SAIL complex as a pH dependent colloidal transport system for controlled transport of a lipophilic dye, Rhodamine 6G (R6G), in aqueous phase, which is supported by confocal laser scanning microscopy (CLSM). In the present work, the effect of functionalization over the alkyl chain of SAILs, modulating the colloidal properties of SAIL-BSA systems, has been explored along with the utilization of these complexes as a pH dependent reversible carrier of lipophilic molecules. It is expected that besides providing basic understanding of colloidal complexes of BSA with SAILs, the present work is expected to be helpful in extending the applications of such colloidal systems for material transport.
Project description:Screening of illicit drugs for new psychoactive substances-namely cathinone-at crime scenes is in high demand. A dual-emission bovine serum albumin-stabilized gold nanoclusters probe was synthesized and used for quantitation and screening of 4-chloromethcathinone and cathinone analogues in an aqueous solution. The photoluminescent (PL) color of the bovine serum albumin-stabilized Au nanoclusters (BSA-Au NCs) probe solution changed from red to dark blue during the identification of cathinone drugs when excited using a portable ultraviolet light-emitting diodes lamp (365 nm). This probe solution allows the PL color-changing point and limit of detection down to 10.0 and 0.14 mM, respectively, for 4-chloromethcathinone. The phenomenon of PL color-changing of BSA-Au NCs was attributed to its PL band at 650 nm, quenching through an electron transfer mechanism. The probe solution was highly specific to cathinone drugs, over other popular illicit drugs, including heroin, cocaine, ketamine, and methamphetamine. The practicality of this BSA-Au NCs probe was assessed by using it to screen illicit drugs seized by law enforcement officers. All 20 actual cases from street and smuggling samples were validated using this BSA-Au NCs probe solution and then confirmed using gas chromatography-mass spectrometry. The results reveal this BSA-Au NCs probe solution is practical for screening cathinone drugs at crime scenes.
Project description:We have investigated charge transport in ZnTPPdT-Pyr (TPPdT: 5,15-di(p-thiolphenyl)-10,20-di(p-tolyl)porphyrin) molecular junctions using the lithographic mechanically controllable break-junction (MCBJ) technique at room temperature and cryogenic temperature (6 K). We combined low-bias statistical measurements with spectroscopy of the molecular levels in the form of I(V) characteristics. This combination allows us to characterize the transport in a molecular junction in detail. This complex molecule can form different junction configurations, having an observable effect on the trace histograms and the current-voltage (I(V)) measurements. Both methods show that multiple, stable single-molecule junction configurations can be obtained by modulating the interelectrode distance. In addition we demonstrate that different ZnTPPdT-Pyr junction configurations can lead to completely different spectroscopic features with the same conductance values. We show that statistical low-bias conductance measurements should be interpreted with care, and that the combination with I(V) spectroscopy represents an essential tool for a more detailed characterization of the charge transport in a single molecule.
Project description:Copper nanoclusters (CuNCs) are attractive for their unique optical properties, providing sensitive fluorescent detection of several kinds of targets even in complex matrices. Their ability in growing on suitable protein and nucleic acid templates make CuNCs efficient optical reporters to be exploited in bioanalysis. In this work, we report the specific and sensitive determination of human serum albumin (HSA) in human serum (HS) and urine via CuNCs fluorescence. HSA is the most abundant protein in plasma, and plays a key role in the early diagnosis of serious pathological conditions such as albuminuria and albuminemia. Recently, HSA has become clinically central also as a biomarker to assess severity, progression, and prognosis of various cancers. We report the controlled and reproducible growth of CuNCs directly on the target analyte, HSA, which results in a fine dose-dependent fluorescent emission at 405 nm. The protocol is optimized in water, and then applied to serum and urine specimens, without matrix pretreatment. The method linearly responds within the whole concentration of clinical interest, with a sensitivity of 1.8 ± 0.1 × 10-3 g L-1 and 0.62 ± 0.03 × 10-3 g L-1 in serum and urine, respectively, and excellent reproducibility (CVav% ca. 3% for both). The assay is designed to have a single protocol working for both matrices, with recovery of 95% (HS) and 96% (urine). The stability of the fluorescence after CuNCs formation was tested over 3 days, displaying good results (yet higher in urine than in serum).