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Background: This study investigates the incidence, disease burden, and risk factors of surgical site infections (SSIs), particularly Multiple Drug-Resistant Organism (MDRO) Infection after colorectal surgery, to provide evidence for the prevention and control of the SSIs after colorectal surgery. Methods: The study included patients undergoing colorectal surgery between January 1, 2020, and December 31, 2021 at Xiangya Hospital Central South University. Data about demographic information, length of hospital stay, cost of hospitalization, underlying diseases, invasive procedures, and antimicrobial use were gathered via Epidata3.1. A multivariate logistic regression model is used to examine the independent risk factors of SSIs and Multidrug organism infections. Results: The study included a total of 2297 colorectal surgery patients; 94 patients experienced SSIs following an operation, including superficial incision infection in 18 cases, deep incision infection in 12 cases, and organ compartment infection in 64 cases. In the infection group, 44 cases have multidrug-resistant pathogens, 10 cases have sensitive pathogens, and 40 cases do not have any identifiable pathogens. The pathogen of SSIs in this study is primarily Escherichia coli. It had high cefazolin and cefuroxime resistance, but low resistance to imipenem and piperacillin tazobactam. The median length of stay and hospital costs in the infection group are 27.5 (day) and 85716.96 (yuan), while these figures are 15 (day) and 56318.06 (yuan) in the control group, respectively. All P-values are Conclusion: The disease burden of SSIs after colorectal surgery is comparatively high, and mechanical ventilation is the independent risk factor for SSIs. MDRO were the most common pathogens of SSIs.

The development of protein-based in situ forming hydrogel remains a big challenge due to the limited chemical groups in proteins. Keratins are a group of cysteine-rich structural protein found abundant in skin and skin appendant. Recently, our lab has established a disulfide shuffling strategy to prepare keratin hydrogels via oxygen (O2) oxidation. However, such hydrogel still needed to be molded in advance. In this work, inspired by the fact that glucose commonly exists in body fluids, a glucose-triggered in situ forming keratin hydrogel was developed based on the disulfide shuffling strategy via a higher oxidation force of hydrogen peroxide (H2O2). The hydrogel precursor solution consisted of keratin, cysteine and glucose oxidase (GOD), which could generate H2O2 in an indirect and mild way via GOD-catalyzed oxidation of glucose in body fluids. Our findings demonstrated that the GOD-catalyzed oxidation method not only shortened the gelation time but improved the mechanical strength of the hydrogel by comparison with O2 oxidation and direct addition of H2O2 solution methods, and realized in situ gelation within 3 min on a full-thickness wound bed in normal mice. Moreover, the in situ forming keratin hydrogel was applied as a drug depot for wound repair, and the deferoxamine-loaded one accelerated healing in the full-thickness wounds of streptozotocin-induced diabetic rats, notably by promoting angiogenesis and neovascularization in wounds. STATEMENT OF SIGNIFICANCE: Studies show that keratin hydrogels possess tissue regeneration capacity, especially in skin wound repair. However, most of the reported keratin hydrogels needed to be molded in advance and cannot fit irregular wound shape. This work describes a glucose-triggered in situ forming keratin hydrogel via a disulfide shuffling strategy under the oxidation of hydrogen peroxide. Of note, the hydrogen peroxide was supplied indirectly by glucose oxidase-catalyzed oxidation of glucose in wound fluids, and this method needed no additional crosslinking agents or chemical modifications on keratins. Our findings showed that this hydrogel realized in situ gelation within 3 min on a full-thickness wound bed and enabled an injectable mode with good filling ability toward irregular wounds. Moreover, this hydrogel could be applied as a drug depot for the treatment of diabetic wounds.

Succinoglycan is an industrially important exopolysaccharide biosynthesized by bacteria. In this study, mutant strain 18052 N-11 was obtained from the wild type strain Rhizobium radiobacter ATCC 19358 by NTG mutagenesis. It has a high yield succinoglycan of 32.5 g/L cultured in a 15 L-fementer for 72 h. Succinoglycan SG-A from the wild type strain has two components, and the molecular weights were 1.55 × 107 Da and 1.26 × 106 Da, respectively. While, succinoglycan SG-N from the mutant strain was a homogeneous polysaccharide, and the molecular weight was 1.01 × 107 Da. The molecular weight of both succinoglycan was higher than those reported in literatures. DSC thermogram of SG-A showed a higher endothermic peak than that of SG-N due to the higher crystallinity of SG-A. The dynamic frequency sweep test of SG-A and SG-N showed that the elastic modulus G' and viscosity modulus G" curves intersected at 65 °C, indicating the thermally induced order-disorder conformation. The results of effect of concentrations (2.5–15%) and temperatures (25–75 °C) on apparent viscosity of SG-A and SG-N showed that the succinoglycan solutions exhibited non-Newtonian, shear-thinning behavior. Both SG-A and SG-N showed an excellent emulsification activity. The characterizations and rheological properties make SG-A and SG-N prominent candidates in food, cosmetics, pharmaceutical and petroleum industries.

Curdlan is a neutral linear exopolysaccharide produced by Agrobacterium spp. under nitrogen-limiting conditions. In this study, we explored the role of glnA in curdlan biosynthesis in Agrobacterium sp. CGMCC 11546. The curdlan production of the ΔglnA strain was impaired, decreasing by 93% compared with that of the wild-type strain after 96 h fermentation. Analysis of fermentation profiles revealed that cell growth and utilization of carbon and nitrogen sources were impaired in the ΔglnA strain. Transcriptome analysis indicated that various of genes involved in curdlan biosynthesis were downregulated after 24 h fermentation in the ΔglnA strain, particularly genes involved in heme synthesis and the electron transport chain, which are essential for energy generation. Metabolomics analysis revealed flavin adenine dinucleotide (FAD) and adenosine diphosphate (ADP) accumulation in the ΔglnA strain, suggesting insufficient energy supply. Furthermore, glnA overexpression led to an 18% increase in the curdlan yield of the ΔglnA mutant compared with that of the wild-type strain after 96 h fermentation. Taken together, the findings demonstrate that glnA plays a vital role in curdlan biosynthesis by supplying ATP via regulating the expression of genes involved in heme synthesis and the electron transport chain.

Objective As nanoscale membrane vesicles, extracellular vesicles (EVs) are actively released by cells and have recently been observed to assume an important role in the treatment of ischemic stroke. However, the source of EVs currently reported for the treatment of ischemic stroke is tightly restricted to mammals. Moreover, these EVs are limited in clinical translation due to the high cost of cell culture. In species other than mammals, Lactobacillus Plantarum culture is low-cost and high-yield. Notwithstanding, it is poorly identified whether Lactobacillus Plantarum-derived EVs (LEVs) can be applied across species for the treatment of ischemic stroke. Methods LEVs were injected into mice via the tail vein immediately after transient middle cerebral artery occlusion (tMCAO) modeling. Infarct volumes, neurological scores, and neuron apoptosis were examined 3 days following the ischemic episode. The expression of microRNA (miRNA) and the target gene in neurons and peri-infarct regions of the post-ischemic brain were measured for mechanistic analyses. Results LEVs crossed the blood-brain barrier and were taken up by neurons both in vitro and in vivo. LEV treatment attenuated neuron apoptosis following oxygen-glucose deprivation (OGD). In vivo findings displayed that LEV treatment substantially reduced neurological deficits and brain infarct size in tMCAO mice. High-throughput sequencing exhibited that miR-101a-3p expression was prominently elevated by LEV treatment in OGD-induced neurons, and corroborating findings were detected in tMCAO mice treated with LEVs. Mechanistically, c-Fos was directly targeted by miR-101a-3p. Moreover, c-Fos manipulated ischemia-induced neuron apoptosis in vitro and in vivo through the TGF-β1 pathway. miR-101a-3p inhibition aggravated ischemia-induced neuron apoptosis in vitro and in vivo, and miR-101a-3p overexpression triggered opposite results. Conclusion Our results elaborated for the first time that LEVs might inhibit neuron apoptosis and injury across species via the miR-101a-3p/c-Fos/TGF-β axis, which may provide novel ideas and targets for the treatment of ischemic stroke and is also of significance for the clinical translation of EVs.

Curdlan is an edible microbial polysaccharide and can be used in food, biomedical and biomaterial fields. To reduce the cost of curdlan production, this study investigated the suitability of cassava starch hydrolysates as carbon source for curdlan production. Cassava starch was hydrolyzed into maltose syrup using β-amylase and pullulanase at various enzyme dosages, temperature, time and addition order of two enzymes. The maltose yield of 53.17% was achieved at starch loading 30% by simultaneous addition β-amylase 210 U/g starch and pullulanase 3 U/g starch at 60 °C for 9 h. Cassava starch hydrolysates were used as carbon source for curdlan production by Agrobacterium sp. DH-2. The curdlan production reached 28.4 g/L with the yield of 0.79 g/g consumed sugar and molecular weight of 1.26 × 10

The aim of this study was to investigate the effect of tumor necrosis factor receptor-related factor 6 (TRAF6) in acute pancreatitis (AP)-induced intestinal barrier injury via the Toll-like receptor 4/nuclear factor kappa-B (TLR4/NF-κB) signal pathway.Rat models of acute edematous pancreatitis (AEP) and acute necrotizing pancreatitis (ANP) were established by intraperitoneal injection of caerulein and retrograde infusion of sodium taurocholate solution into the biliopancreatic duct, respectively. Separate groups of model rats were pretreated with the TRAF6 inhibitor, MG-132. Rats were sacrificed at 12 h after the last injection for inducing AP. Histopathological changes, inflammatory response, intestinal barrier function, and protein expression levels were assessed by pathological score, ELISA, TUNEL, qRT-PCR, immunohistochemistry and western blotting.Rat models of AEP and ANP were successfully established as evidenced by the pathological changes in the pancreas and intestine. Pre-treatment with MG-132 significantly alleviated pancreatic and intestinal pathological scores, reduced serum levels of amylase, IL-1β, and IL-6, and ameliorated apoptosis of mucosal cells. MG-132 reduced intestinal barrier injury, including serum levels of diamine oxidase and lipopolysaccharide, and intestinal expressions of ZO-1 and occludin. Moreover, it significantly suppressed the activation of the intestinal TLR4/NF-κB signaling pathway.TRAF6 inhibitor alleviated pancreatic and intestinal injury in AEP and ANP. This effect may be mediated through inhibition of the TLR4/NF-κB signaling pathway, which in turn regulates the inflammatory response and intestinal barrier injury.

Protein-templated gold nanoclusters have attracted attention in fluorescence imaging due to their simple synthesis and good biocompatibility. However, limitations still exist such as poor colloid stability and undesirable fluorescence intensity. Here we describe the self-assembly of keratin-templated gold nanoclusters via a simple and mild preparation process, including keratin-templated synthesis of gold nanoclusters (AuNCs@Keratin), silver ions modification of AuNCs@Keratin (AuNCs-Ag@Keratin), and gadolinium ions-induced aggregation of AuNCs-Ag@Keratin (AuNCs-Ag@Keratin-Gd). It was demonstrated that the AuNCs-Ag@Keratin-Gd obtained an enhanced fluorescence intensity (6.5 times that of AuNCs@Keratin), high colloid stability for more than 4 months, and good biocompatibility. Moreover, the AuNCs-Ag@Keratin-Gd holds promise in multifunctional applications such as near-infrared (NIR) fluorescence imaging, magnetic resonance (MR) imaging, and redox-responsive drug delivery, extending the applicability of fluorescent gold nanoclusters, especially in biomedical fields. Statement of significance Assembly-induced fluorescence enhancement has been rarely reported on as it relates to the protein-templated gold nanoclusters (AuNCs). In this work, self-assembly of protein-templated AuNCs was developed for enhanced fluorescence intensity and multifunctional applications, including bioimaging and responsive drug delivery. A cysteine-rich protein, keratin, was utilized as the template to synthesize AuNCs, which underwent silver ion modification and gadolinium ion-induced aggregation. The silver modification of the keratin-templated AuNCs facilitated the formation of a dense aggregate after gadolinium ion-induced assembly, thus generating an enhanced fluorescence intensity. Such a mechanism was confirmed by fluorescence correlation spectroscopy analysis. We believe that this work will extend the applicability of the fluorescent gold nanoclusters, especially in biomedical fields, and provided an effective approach for the mechanism analysis of the assembly-induced fluorescence enhancement via fluorescence correlation spectroscopy.

An edible and structured emulsion gel was successfully prepared from thermo-gelable polysaccharide curdlan and regenerated cellulose (RC), which was characterized by a set of methods, such as, fluorescence microscopy, rheology analysis, etc. The preparation procedures included formulating an oil-in-water emulsion stabilized by RC and curdlan, followed by heat treatment leading to a structured solid system. The stable O/W type emulsion gel was acquired at the RC concentration above 0.5 wt % and curdlan above 1 wt %. The fluorescence microscopy proved the adsorption of RC on the oil droplets surface. Besides, the effect of temperature and RC/curdlan concentrations on the rheological behavior of emulsion gel was evaluated. G′, G″ and viscosity of the emulsion started to increase at around 50 °C and thermal irreversible gel formed at temperature 80 °C. Due to the reinforcement of entanglements and interactions, increasing RC/curdlan concentration contributed to an improvement of storage (G’) and loss (G”) moduli in emulsion gel, while reduced their creep compliance under microstress according to the creep measurements.

Currently, the reported source of extracellular vesicles (EVs) for the treatment of ischemic stroke（IS）is limited to mammals. Moreover, these EVs are restricted to clinical translation by the high cost of cell culture. In this respect, Lactobacillus plantarum culture is advantaged by low cost and high yield. However, it is poorly understood whether Lactobacillus plantarum-derived EVs (LEVs) are applicable for the treatment of IS. Here, our results demonstrated that LEVs reduced apoptosis in ischemic neuron both in vivo and in vitro. As revealed by high-throughput sequencing, miR-101a-3p expression was significantly elevated by LEV treatment in OGD/R-induced neurons, as confirmed in the tMCAO mice treated with LEVs. Mechanistically, c-Fos was directly targeted by miR-101a-3p. In addition, c-Fos determined ischemia-induced neuron apoptosis in vivo and in vitro through the TGF-β1 pathway, miR-101a-3p inhibition aggravated ischemia-induced neuron apoptosis in vitro and in vivo, and miR-101a-3p overexpression produced the opposite results. Hsa-miR-101-3p was downregulated in the plasma of patients with IS but upregulated in the patients with neurological recovery after rt-PA intravenous thrombolysis. In conclusion, Our results demonstrated for the first time that LEVs might inhibit neuron apoptosis via the miR-101a-3p/c-Fos/TGF-β axis, and has-miR-101-3p is a potential marker of neurological recovery in IS patients.

Injectable hydrogels hold promise in biomedical applications due to their noninvasive administration procedure and capacity enabling the filling of irregularly shaped defects. Protein-based hydrogels provide features including good biocompatibility and inherent biofunction. However, challenges still remain to develop a protein-based injectable hydrogel in a convenient way due to the limited active groups in proteins. Keratins are a group of cysteine-rich structural proteins found abundantly in skin and skin appendages. In this work, we utilized keratin and the Au(III) salt to develop an injectable hydrogel based on the dynamic exchange between disulfide bonds (S–S) and gold(I)–thiolates (Au–S). Such a hydrogel could be prepared at the physiological pH and applied as an injectable hydrogel for biomedical applications including hemostatic and wound dressing materials. Our findings demonstrated that this keratin injectable hydrogel showed a good hemostatic effect in both tail amputation and liver injury models. Moreover, it was proved efficient as a drug loading carrier, and the deferoxamine-loaded hydrogel showed a desirable wound healing effect in a full-thickness excision wound model.

Curdlan is a water-insoluble exopolysaccharide produced by Agrobacterium species under nitrogen starvation. The curdlan production in the ΔmdeA, ΔmetA, ΔmetH, and ΔmetZ mutants of methionine biosynthesis pathway of Agrobacterium sp. CGMCC 11546 were significantly impaired. Fermentation profiles of four mutants showed that the consumption of ammonia and sucrose was impaired. Transcriptome analysis of the ΔmetH and ΔmetZ mutants showed that numerous differentially expressed genes involved in the electron transfer chain (ETC) were significantly down-regulated, suggesting that methionine biosynthesis pathway affected the production of energy ATP during the curdlan biosynthesis. Furthermore, metabolomics analysis of the ΔmetH and ΔmetZ mutants showed that ADP and FAD were significantly accumulated, while acetyl-CoA was diminished, suggesting that the impaired curdlan production in the ΔmetH and ΔmetZ mutants might be caused by the insufficient supply of energy ATP. Finally, the addition of both dibasic sodium succinate as a substrate of FAD recycling and methionine significantly restored the curdlan production of four mutants. In conclusion, methionine biosynthesis pathway plays an important role in curdlan biosynthesis in Agrobacterium sp. CGMCC 11546, which affected the sufficient supply of energy ATP from the ETC during the curdlan biosynthesis.

Curdlan has wide potential application in the food and biomedical fields due to its unique thermal gel and biological activity. This study investigated the effect of six sugars including glucose, fructose, lactose, maltose, sucrose and xylose as carbon sources on production and properties of curdlan using

In this paper, the pulse wave (PW) rectifier of the Schottky diode is theoretically analyzed using the microwave equivalent circuit. It is found that the duty cycle of PW is inversely proportional to the load resistance of the rectifier when the amplitude of the input pulse is the same. Therefore, a stable high-efficiency rectifier can be designed by changing the value of the load resistance when the duty cycles are different. A grounded coplanar waveguide (GCPW) rectifier for the pulse wave is designed to verify this rule. The rectifier is simulated by ADS software and verified by the measurements. When the duty cycle of PW varies from 0.01 to 1 and the input pulse amplitude is stable at the operation frequency of 2.38 GHz, the measured rectifying efficiency can be maintained at the peak efficiency of 76.1% by adjusting the load resistance. However, when the input signal of the rectifier is the continuous wave (CW), the rectifying efficiency is only 3.9% at the same input power amplitude. The proposed rectifier has a simple structure so that it can obtain a high efficiency and has a compact size of 0.22λ0 × 0.11λ0. It can be a good candidate for simultaneous wireless information and power transmission (SWIPT) for low-power electronic devices in the Internet of Things (IoT).

Cured isotropic conductive adhesive (ICA) with different conductive fillers (micro silver flakes) contents were prepared. Based on the loading mode of “rapid loading-holding-rapid unloading” and semi-empirical method from the generalized Kelvin model, micro-indentation tests were carried out to investigate the effect of hygrothermal aging on the mechanical properties of cured ICA. On the whole, the elastic modulus and hardness of cured ICA with high silver content are relatively larger. As the hygrothermal aging time increases, both elastic modulus and hardness decrease at first and then stabilize, and the creep deformation is more evident. Indentation creep displacement–time curves for cured ICA were characterized by the generalized Kelvin model. During the holding stage, creep compliance increases slowly at first and then increases quickly with modulus loss. With the aggravated aging creep compliance increases, and creep compliance of cured ICA with high silver content increases faster at the later stage of hygrothermal aging. The widened retardation peaks with increasing retardation time reflect the different retardation processes during the holding stage. With increasing aging time, the creep rate sensitivity exponent increases and creep resistance reduces accordingly.

Curdlan has wide potential application in the food and biomedical fields due to its unique thermal gel and biological activity. This study investigated the effect of six sugars including glucose, fructose, lactose, maltose, sucrose and xylose as carbon sources on production and properties of curdlan using Agrobacterium sp. DH-2. The maximum production (38.1 g/L and 37.4 g/L, respectively) and yield (0.58 g curdlan/g sucrose and 0.53 g curdlan/g maltose, respectively) of curdlan were achieved by sucrose and maltose, followed by glucose, fructose, lactose and xylose. Scanning electron micrographs showed that the surface of cells was smooth in strain growth phase, while cells were covered by curdlan matrix acted as a net in the curdlan synthesis phase. The highest glucosyltransferase activity (19.9 U/g biomass) corresponded to the maximum curdlan production using the sucrose medium. The molecular weight and gel strength of curdlan were influenced by the carbon sources. The curdlan from xylose medium resulted in a maximum molecular weight of 1.59 × 106 Da and the highest gel strength of 989.2 g/cm2, while the curdlan from sucrose medium resulted in a lowest molecular weight of 1.10 × 106 Da and gel strength of 672.8 g/cm2. The high molecular weight of curdlan had high gel strength.

Curdlan is a bacterial, water-insoluble, linear homopolysaccharide that has been widely used in the food industry. In this study, genome information of strain CGMCC 11546, a UV-induced high-yield mutant of the model curdlan-producing strain Agrobacterium sp. ATCC 31749, was used to investigate the molecular mechanism of curdlan biosynthesis. The maximum curdlan yield of 47.97 ± 0.57 g/L was obtained from strain CGMCC 11546 by using optimal media containing 60 g/L sucrose, 6 g/L yeast, 2 g/L KH2PO4, 0.4 g/L MgSO4·7H2O, 2 g/L CaCO3, 0.1 g/L FeSO4·7H2O, 0.04 g/L MnSO4, and 0.02 g/L ZnCl2 at 30 °C and 280 rpm after 96 h of fermentation. The gel strength of curdlan was improved by 41 % by knocking out the β-1,3-glucanase genes exoK and exsH of strain CGMCC 11546. Furthermore, the application of curdlan from the ΔexoK-exsH strain in noodles significantly improved the eating quality of both raw and cooked noodles.

In this work, different concentrations of Se-incorporated mesoporous silica nanospheres (MSNs) (5Se/MSNs and 10Se/MSNs) were successfully synthesized via an in-situ one-pot method. Their physicochemical properties were characterized by X-ray diffraction (XRD), transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The release behaviors of Se and Si were investigated in a phosphate-buffered saline (pH = 5.5, 7.4) solution (PBS). In vitro antibacterial properties of the prepared samples were evaluated with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The cytocompatibilities of the samples were then assessed using L929 cells. Se nanoparticles were successfully loaded onto the outer and inner surfaces of hierarchical mesoporous silica. The sizes of the Se/MSNs nanoparticles were approximately 120 nm for 5Se/MSNs and 210 nm for 10Se/MSNs. The XRD and XPS results showed that Se mainly existed in the form of Se0 in the samples. The Se/MSNs exhibited stable and sustained release of both Si and Se in PBS solution. In vitro antibactericidal tests indicated that the Se/MSNs could exhibit better antibacterial activity against S. aureus than pure Se nanoparticles after 6 and 24 h of culturing. The minimal inhibitory concentration (MIC) of 10Se/MSN was 100 μg mL-1. However, the Se/MSNs exhibited no inhibitory effect on E. coli bacteria. Furthermore, all the samples exhibited excellent cell viability. These studies demonstrate initial in vitro antibacterial activity and good cytocompatibility of Se/MSNs and their potential application in antibacterial nanomedicine.

A novel ordered TiO2 nanodot array on 316LSS (NTA/316LSS) was first prepared by sol-gel in situ growth method. The surface microstructure, chemical components, antibacterial activity and cytocompatibility of the samples were characterized. The results showed that anatase TiO2 nanogranules (45 ± 5 nm) were embedded into nanopits (50 ± 5 nm) and arrayed in an ordered manner. The in vitro antibacterial test showed that there was a 96.3 ± 2.4% reduction in E. coli on the NTA/316LSS surface and a 98.1 ± 1.3% reduction in S. aureus compared to that on untreated 316LSS controls. Furthermore, NTA/316LSS showed good cytocompatibility in vitro. Our study revealed that such TiO2 nanodot surface can be designed to improve the use of 316LSS for various implant application.

Protein-templated gold nanoclusters (AuNCs) have attracted attention in fluorescence imaging due to their simple synthesis process and good biocompatibility. However, limitations still exist such as undesirable fluorescence intensity and poor colloid stability. In recent years, assembly-induced fluorescence enhancement via an aggregate approach was proved efficient on peptides- or other small molecules-templated AuNCs, while few were achieved on the protein-templated AuNCs. We hypothesized that the reported self-assembly strategy gave a loose aggregate of the protein-templated AuNCs, thus resulting in weak aurophilic interaction and no obvious enhancement in the fluorescence intensity. Our group has prepared a red emission AuNCs using keratin, a type of naturally occurring cysteine-rich protein, as the template (AuNCs@Keratin). Inspired by the unique characteristic of keratins, in this work, we develop a self-assembly strategy via a simple and mild approach, including silver ions modification and gadolinium ions-induced aggregation of AuNCs@Keratin. It should be mentioned that the silver modification of AuNCs@Keratin facilitated the formation of a dense aggregate after Gd ions-induced assembly, thus generating an enhanced fluorescence intensity. Such a mechanism was confirmed by the fluorescence correlation spectroscopy analysis. We demonstrated that the assembly of AuNCs@Keratin obtained an enhanced fluorescence intensity (6.5 times that of AuNCs@Keratin), excellent colloid stability for more than 4 months, and good biocompatibility. Moreover, such nanoparticles hold promise in multifunctional applications including near-infrared (NIR) fluorescence imaging, magnetic resonance (MR) imaging, and redox-responsive drug delivery, extending the applicability of fluorescent gold nanoclusters, especially in biomedical fields.

Protein-based hydrogels that possess tunable properties have long been a challenge in tissue engineering. Keratin is a group of natural proteins derived from skin and skin appendant, and features a rich content of cysteine residue which exists in the form of disulfide bonds. Inspired by this, in this work, a simple disulfide shuffling strategy was utilized to develop keratin hydrogels by converting the intramolecular disulfide bonds into the intermolecular disulfide bonds. To achieve this, the intramolecular disulfide bonds were first cleaved by the reductive reagent such as cysteine, to liberate free thiol group, which formed intermolecular disulfide bonds through thiol oxidation. It was demonstrated that control of the cysteine level led to a tunable disulfide crosslinking density, and thus an altered network structure, gel degradation, and drug release rate. Also, this strategy enables good biocompatibility of the material owing to avoiding extra chemical crosslinkers in the preparation procedure. Moreover, this keratin hydrogel had redox-responsive capacity in both gel degradation and drug release due to the disulfide-bond based network structure, providing extensive applicability in tissue engineering and drug release.

Intermetallic compounds (IMCs) at the Sn–3.0Ag–0.5Cu/Cu joint interface were prepared through reflow soldering and isothermal aging in a QHL360 SMT fully automatic reflow soldering system and a high-temperature test chamber, respectively. The mechanical properties of IMCs were then studied and characterized by nanoindentation. The mechanical responses of both Cu6Sn5 and Cu3Sn (IMCs) show large dependence on the strain rate during loading. In addition, multiple pop-in events are observed in Cu6Sn5 but not evident in Cu3Sn. During loading, the contact stiffness of IMCs increases almost linearly with the indentation depth under each strain rate. In total, the hardness and elastic modulus of Cu3Sn are larger than those of Cu6Sn5, and the hardness of both Cu6Sn5 and Cu3Sn increase with increasing strain rate. During the holding stage, creep deformations of IMCs increase as loading strain rate increases. Indentation creep displacement–time curves for Cu6Sn5 and Cu3Sn can be well described by the generalized Kelvin model. The lower creep rate sensitivity exponent of Cu3Sn implies its relatively higher creep resistance. Keywords: Intermetallic compounds, Nanoindentation, Mechanical properties, Strain rate, Creep