ABSTRACT
Postoperative atrial fibrillation (POAF) is a common complication following cardiac surgery, which often occurs within 30 postoperative days, especially peaking at 2-3 days. Antiarrhythmic medications such as amiodarone are recommended in clinical practice for the prophylaxis and treatment of POAF. However, conventional oral administration is hindered due to delayed drug action and high risks of systemic toxicity, and emerging localized delivery strategies suffer from a limited release duration (less than 30 days). Herein, we develop a microneedle (MN) patch for localized delivery of amiodarone to the atria in a "First Rapid and Then Sustained" dual-release mode. Specifically, this patch is composed of a needle array integrated with an amiodarone-loaded reservoir for a sustained and steady release for over 30 days; and an amiodarone-containing coating film deposited on the needle surface via the Langmuir-Blodgett technique for a rapid release at the first day. Upon this design, only one MN patch enables a higher drug accumulation in the atrial tissue at the first day than oral administration and simultaneously remains therapeutical levels for over 30 days, despite at a significantly reduced drug dosage (5.08 mg in total versus â¼10 mg per day), thereby achieving ideal preventive effects and safety in a rat model. Our findings indicate that this MN device provides a robust and efficient delivery platform for long-term prophylaxis of POAF.
Subject(s)
Atrial Fibrillation , Needles , Atrial Fibrillation/prevention & control , Atrial Fibrillation/drug therapy , Animals , Rats , Rats, Sprague-Dawley , Amiodarone/administration & dosage , Amiodarone/chemistry , Anti-Arrhythmia Agents/administration & dosage , Anti-Arrhythmia Agents/chemistry , Anti-Arrhythmia Agents/pharmacology , Male , Drug Delivery Systems , Postoperative Complications/prevention & controlABSTRACT
Physical hydrogels of natural polysaccharides are considered as ideal candidates for wound dressing due to their natural biological activity and no harmful cross-linking agents. However, it remains a challenge to fabricate such hydrogel dressings in a facile and low-cost way. Herein, we reported an easy and cost-effective method to construct CO2-mediated alkali-neutralization Curdlan (CR) hydrogels without using an external cross-linking agent. Two types of hydrogels (denoted as CR-NaOH and CR-Na3PO4, respectively) were fabricated by dissolving CR powders in a NaOH or Na3PO4 aqueous solution, followed by keeping the CR alkaline solutions in air. The obtained pure CR hydrogels possessed a tunable porous structure with walls containing different forms of nanofibrils. These hydrogels exhibited much higher gel strength by comparison with the gels prepared by conventional heating treatment. They were flexible, stretchable, twistable, and conformable to arbitrarily curved skins. Moreover, they exhibited ideal swellability, proper degradability, and water vapor transmission rate, and their physicochemical properties were closely related to CR concentration in the alkaline solution. These two hydrogels also supported the growth of L929 cells. Importantly, studies on wound healing revealed that both 3CR-NaOH and 3CR-Na3PO4 hydrogels were capable of accelerating the wound healing process through recruiting more macrophages/fibroblasts, inducing more collagen deposition and neovascularization (α-SMA and CD31) without carrying any exogenous bioactive components. In conclusion, the present work not only reported promising materials for application in wound therapy but also offered a facile and safe manufacturing procedure for generating pure CR physical hydrogels with better performance.
Subject(s)
Carbon Dioxide , Hydrogels , beta-Glucans , Hydrogels/pharmacology , Hydrogels/chemistry , Sodium Hydroxide/pharmacology , Wound Healing , Anti-Bacterial Agents/pharmacologyABSTRACT
The multi-layer terahertz metasurfaces are designed to achieve polarization-insensitive electromagnetically induced transparency (EIT) effect and its sensing performance based on spoof localized surface plasmons (S-LSPs). The unit cell of the proposed metasurfaces is comprised of a metallic spiral (MS) structure, square metal frame (SMF) structure, and vanadium dioxide (VO2) layer. The EIT effect is realized by the bright-bright coupling between spoof electric localized surface plasmons (S-ELSPs) and electric dipole, which can be proved by the multipole scattering theory. The maximum value of transmission amplitude at the transparent window is 0.91, and the modulation depth can reach 51% by adjusting the conductivity of VO2. The theoretical results based on the two-particle model show excellent agreement with the simulated results. Moreover, the change of polarization angle has little effect on the EIT effect and the proposed metasurfaces show polarization-insensitive characteristics. The slow light effect of the proposed metasurfaces can also be dynamically controlled by tuning the conductivity of VO2. Due to the high Q value of the transparent window, the proposed metasurfaces exhibit excellent sensing performance, and the sensitivity is 0.172 THz RIU-1. Our study provides a method for the fabrication of EIT metasurfaces and has a broad application prospect in slow light devices, sensors, and modulators.
ABSTRACT
A high-transmission and large group delay terahertz triple-band electromagnetically induced transparency (EIT) effect is obtained in a metal-perovskite hybrid metasurface, which consists of a cross metal (CM), a pair of square metal frames (SMFs), and a pair of square split rings (SSRs). The results reveal that the transmission amplitudes of three transparent windows are 0.83, 0.9, and 0.89. The maximum values of group delays at three transparent windows are 7.64 ps, 4.07 ps, and 4.27 ps. The multipole scattering theory shows that the first and third transparent windows are created by the coupling between the electric dipole and toroidal dipole, and the second transparent window is created by the electric dipoles. The triple-band EIT effect can be dynamically controlled by adjusting the conductivity of perovskite while the modulation depths are 49.4%, 41%, and 31.5%. Moreover, the slow light effect can also be tunable by tuning the conductivity of perovskite while the modulation depths are 87.8%, 65.6%, and 68.4%. Our study puts forward a novel design concept for multi-band EIT effect and shows great prospects in the application of multi-band devices.
ABSTRACT
A tunable and three-dimensional dual-band metamaterial absorber based on electromagnetically induced transparency (EIT) is proposed. The unit cell of the metamaterial absorber consisted of a cut wire (CW), two split ring resonators (SRRs), a metal plate and a patterned vanadium dioxide (VO2) film. The two absorption peaks could be dynamically controlled by tuning the conductivity of VO2 with the maximum absorptions of 97.5% at 1.05 THz and 96.5% at 1.16 THz. The physical mechanism of the metamaterial absorber was explained by the electric field, magnetic field, power loss density and surface current distributions. In addition, the metamaterial absorber exhibited a wide polarization angle for y-polarization wave and x-polarization wave and showed good robustness against oblique incidence. Moreover, the metamaterial absorber exhibited a high fault tolerance with a variation in the geometric parameters. Our work provides a novel method for the fabrication of multi-band metamaterial absorbers and has promising applications in terahertz sensors, modulators and filters.
ABSTRACT
Currently, the reported source of extracellular vesicles (EVs) for the treatment of ischemic strokeï¼ISï¼is 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-ß1 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-ß axis, and has-miR-101-3p is a potential marker of neurological recovery in IS patients.
Subject(s)
Brain Injuries , Extracellular Vesicles , Lactobacillus plantarum , MicroRNAs , Animals , Apoptosis , Extracellular Vesicles/metabolism , Lactobacillus plantarum/genetics , Lactobacillus plantarum/metabolism , Mammals/metabolism , Mice , MicroRNAs/genetics , MicroRNAs/metabolism , Proto-Oncogene Proteins c-fos/genetics , Transforming Growth Factor betaABSTRACT
BACKGROUND: 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. METHODS: 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. RESULTS: 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-1ß, 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. CONCLUSIONS: 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.
Subject(s)
Intestines , NF-kappa B , Pancreatitis, Acute Necrotizing , TNF Receptor-Associated Factor 6 , Toll-Like Receptor 4 , Animals , Intestines/metabolism , Intestines/pathology , NF-kappa B/metabolism , Pancreatitis, Acute Necrotizing/metabolism , Pancreatitis, Acute Necrotizing/pathology , Rats , Signal Transduction , TNF Receptor-Associated Factor 6/antagonists & inhibitors , TNF Receptor-Associated Factor 6/metabolism , Toll-Like Receptor 4/metabolismABSTRACT
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 ß-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 ß-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 × 106 Da at 96 h with cassava starch hydrolysate at 90 g/L initial sugar concentration. Curdlan produced from cassava starch hydrolysates was characterized using FT-IR spectra and thermo gravimetric analysis. This work indicated that cassava starch was a potential renewable feedstock for curdlan production.
Subject(s)
Manihot , beta-Amylase , Agrobacterium , Carbon , Maltose , Spectroscopy, Fourier Transform Infrared , Starch , beta-GlucansABSTRACT
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.
Subject(s)
Agrobacterium/physiology , Biosynthetic Pathways , Methionine/metabolism , Mutation , beta-Glucans/metabolism , Adenosine Triphosphate/metabolism , Agrobacterium/genetics , Bacterial Proteins/genetics , Fermentation , Gene Expression Profiling , Gene Expression Regulation, Bacterial , Metabolomics , Nitrogen/metabolismABSTRACT
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.
Subject(s)
Hemostatics , Hydrogels , Bandages , Keratins , Wound HealingABSTRACT
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.
Subject(s)
Diabetes Mellitus, Experimental , Hydrogels , Keratins/therapeutic use , Wound Healing , Animals , Diabetes Mellitus, Experimental/drug therapy , Glucose , Hydrogen Peroxide , Mice , RatsABSTRACT
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.
Subject(s)
Agrobacterium tumefaciens/metabolism , Polysaccharides, Bacterial/chemistry , Viscosity , Agrobacterium tumefaciens/genetics , Carbohydrate Conformation , Elastic Modulus , Hot Temperature , Mutation , Polysaccharides, Bacterial/biosynthesis , RheologyABSTRACT
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.
Subject(s)
Agrobacterium/metabolism , Bacterial Proteins/metabolism , Glutamate-Ammonia Ligase/metabolism , beta-Glucans/metabolism , Agrobacterium/genetics , Bacterial Proteins/genetics , Glutamate-Ammonia Ligase/genetics , MutationABSTRACT
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 ß-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.
Subject(s)
Agrobacterium/enzymology , Agrobacterium/genetics , Genome, Bacterial , Polysaccharides, Bacterial/metabolism , beta-Glucans/metabolism , Agrobacterium/radiation effects , Bacterial Proteins/genetics , Culture Media/chemistry , Dietary Supplements , Fermentation , Food Quality , Gels/chemistry , Gene Deletion , Glucan 1,3-beta-Glucosidase/genetics , Molecular Weight , Organisms, Genetically Modified , Ultraviolet Rays , Whole Genome Sequencing/methodsABSTRACT
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.
Subject(s)
Agrobacterium/metabolism , Industrial Microbiology , beta-Glucans/metabolism , Agrobacterium/enzymology , Carbon/metabolism , Culture Media/metabolism , Glucosyltransferases/metabolism , Maltose/metabolism , Sucrose/metabolismABSTRACT
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.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Nanoparticles/chemistry , Selenium/pharmacology , Silicon Dioxide/pharmacology , Staphylococcus aureus/drug effects , Animals , Anti-Bacterial Agents/chemistry , Cell Line , Mice , Microbial Sensitivity Tests , Particle Size , Porosity , Selenium/chemistry , Silicon Dioxide/chemistry , Surface PropertiesABSTRACT
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.
Subject(s)
Gold/chemistry , Keratins/chemistry , Metal Nanoparticles/chemistry , Spectrometry, Fluorescence , Animals , Biocompatible Materials/chemistry , Cell Line, Tumor , Cell Survival , Colloids/chemistry , Drug Delivery Systems , Endocytosis , Gadolinium/chemistry , Humans , Magnetic Resonance Imaging , Mice, Inbred C57BL , Silver/chemistryABSTRACT
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.
Subject(s)
Disulfides/chemistry , Drug Carriers/chemistry , Hydrogels/chemistry , Keratins/chemistry , Tissue Scaffolds/chemistry , Animals , Biocompatible Materials/chemistry , Cell Line , Cell Survival/drug effects , Cross-Linking Reagents/chemistry , Cysteine/chemistry , Drug Liberation , Materials Testing/methods , Mice , Mice, Inbred ICR , Molecular Structure , Oxidation-Reduction , Rats , Rheology , Structure-Activity Relationship , Tissue Engineering/methodsABSTRACT
To study the tetragonal-to-monoclinic (T-M) phase transformation behavior under different strain rates and indentation depths, nanoindentation tests were performed on stabilized zirconia ceramics with Continuous Stiffness Measurements. The results indicate decreased phase transformation velocities at both lower and higher strain rates, but increased velocity under medium strain rate during loading. The phase transformation process is sensitive to P/P but the final volume fractions are almost identical (45%). Furthermore, most of the phase transformation is completed during a short initial time followed by slight linear increase of the M-phase volume fraction with holding time. The phase transformation continuously slowed with increasing indentation depth when indented with a constant strain rate.