Silk Fibroin Peptide Research Articles

An engineered Pichia pastoris platform for the biosynthesis of silk-based nanomaterials with therapeutic potential

Silk fibroin (SF) from the cocoon of silkworm has exceptional mechanical properties and biocompatibility and is used as a biomaterial in a variety of fields. Sustainable, affordable, and scalable manufacturing of SF would enable its large-scale use. We report for the first time the high-level secretory production of recombinant SF peptides in engineered Pichia pastoris cell factories and the processing thereof to nanomaterials. Two SF peptides (BmSPR3 and BmSPR4) were synthesized and secreted by P. pastoris using signal peptides and appropriate spacing between hydrophilic sequences. By strain engineering to reduce protein degradation, increase glycyl-tRNA supply, and improve protein secretion, we created the optimized P. pastoris chassis PPGSP-8 to produce BmSPR3 and BmSPR4. The SF fed-batch fermentation titers of the resulting two P. pastoris cell factories were 11.39 and 9.48 g/L, respectively. Protein self-assembly was inhibited by adding Tween 80 to the medium. Recombinant SF peptides were processed to nanoparticles (NPs) and nanofibrils. The physicochemical properties of nanoparticles R3NPs and R4NPs from the recombinant SFs synthesized in P. pastoris cell factories were similar or superior to those of RSFNPs (Regenerated Silk Fibroin NanoParticles) originating from commercially available SF. Our work will facilitate the production by microbial fermentation of functional SF for use as a biomaterial.

Molecular mechanism analysis of apoptosis induced by silk fibroin peptides

Silk fibroin derived from silkworm cocoons exhibits excellent mechanical properties, good biocompatibility, and low immunogenicity. Previous studies showed that silk fibroin had an inhibitory effect on cells, suppressing proliferation and inducing apoptosis. However, the source of the toxicity and the mechanism of apoptosis induction are still unclear. In this study, we hypothesized that the toxicity of silk fibroin might originate from the crystalline region of the heavy chain of silk fibroin. We then verified the hypothesis and the specific induction mechanism. A target peptide segment was obtained from α-chymotrypsin. The potentially toxic mixture of silk fibroin peptides (SFPs) was separated by ion exchange, and the toxicity was tested by an MTT assay. The results showed that SFPs obtained after 4 h of enzymatic hydrolysis had significant cytotoxicity, and SFPs with isoelectric points of 4.0–6.8 (SFPα II) had a significant inhibitory effect on cell growth. LC-MS/MS analysis showed that SFPα II contained a large number of glycine-rich and alanine-rich repetitive sequence polypeptides from the heavy-chain crystallization region. A series of experiments showed that SFPα II mediated cell death through the apoptotic pathway by decreasing the expression of Bcl-2 protein and increasing the expression of Bax protein. SFPα II mainly affected the p53 pathway and the AMPK signaling pathway in HepG2 cells. SFPα II may indirectly increase the expression of Cers2 by inhibiting the phosphorylation of EGFR, which activated apoptotic signaling in the cellular mitochondrial pathway and inhibited the Akt/NF-κB pathway by increasing the expression of PPP2R2A.

MXene and silk fibroin peptide team up to build a 1+1>2 in situ SEI film

The utilization of solid-state lithium-ion batteries (SLIBs) is envisaged for the next generation of energy storage devices due to their exceptional energy density. Nonetheless, for practical applications of SLIBs, it is crucial to address the challenges associated with unstable interfaces and poor electrochemical performance. By employing silk fibroin peptide (SFP) and MXene, we successfully achieved the in-situ generation of uniform solid electrolyte interphase (SEI) films through the design of modified interfaces. The incorporation of -NH2 groups from SFP and the -F terminus from MXene facilitated the formation of Li3N and LiF, thereby enabling selective localization and controlled SEI film growth as confirmed by the time-of-flight secondary-ion mass spectrometry (TOF-SIMS) analysis. The Derjaguin-Müller-Toporov (DMT) modulus demonstrated the robustness of the SEI film. This phenomenon enhances interfacial stability, promotes lithium-ion nucleation, suppresses dendrite growth, and improves overall electrochemical performance during battery operation. The presence of -NH2 possessing a lone pair of electrons exhibited excellent lithophile properties that facilitated micro-complexes formation with lithium ions, thereby promoting lithium salt dissociation and facilitating the lithium-ion migration within systems. Furthermore, the interface-modified polymer electrolytes (PEs) demonstrated an impressive ionic conductivity of up to 1.16 × 10−3 S cm−1, along with a favorable transference number of lithium ions (tLi+) of 0.57. Notably, the modified PEs significantly contributed to stable battery operation at room temperature (RT), exhibiting an initial discharge capacity of 117.6 mAh g−1 at 5 C. This innovative strategy involving modification at the interface level represents a significant advancement towards achieving stable operation in high-energy SLIBs.

Silk fibroin peptide self-assembled nanofibers delivered naringenin to alleviate cisplatin-induced acute kidney injury by inhibiting mtDNA-cGAS-STING pathway.

Silk fibroin (SF) has excellent biocompatibility and biodegradability as a biomaterial. The purity and molecular weight distribution of silk fibroin peptide (SFP) make it more suitable for medical application. In this study, SFP nanofibers (molecular weight ∼30kD) were prepared through CaCl2/H2O/C2H5OH solution decomposition and dialysis, and adsorbed naringenin (NGN) to obtain SFP/NGN NFs. In vitro results showed that SFP/NGN NFs increased the antioxidant activity of NGN and protected HK-2cells from cisplatin-induced damage. In vivo results also showed that SFP/NGN NFs protected mice from cisplatin-induced acute kidney injury (AKI). The mechanism results showed that cisplatin induced mitochondrial damage, as well as increased mitophagy and mtDNA release, which activated the cGAS-STING pathway and induced the expression of inflammatory factors such as IL-6 and TNF-α. Interestingly, SFP/NGN NFs further activated mitophagy and inhibited mtDNA release and cGAS-STING pathway. Demonstrated that mitophagy-mtDNA-cGAS-STING signal axis was involved in the kidney protection mechanism of SFP/NGN NFs. In conclusion, our study confirmed that SFP/NGN NFs are candidates for protection of cisplatin-induced AKI, which is worthy of further study.

Litchi-like silver nanoparticles immobilized in microspheres for effective bacteriostasis, rapid hemostasis, and wound healing

Metal nanoparticles, particularly silver nanoparticles (AgNs), exhibit excellent antibacterial properties. However, their high mobility and Ag+ release rate can damage normal tissues and cells. Therefore, their application in wound healing is limited. Reducing Ag+ to AgNs using tannic acid (TA) and Fe complexes (TA/Fe) could effectively prevent the migration of AgNs and slow the release of Ag+ to achieve effective inhibition of bacteria. Ag+ was reduced to AgNs using TA/Fe coating on the surface of calcium alginate and silk fibroin peptide microspheres (CA/SP) to prepare novel litchi-like microspheres (CA/SP@AgNs). CA/SP@AgNs showed good biocompatibility. The growth and reproduction of Staphylococcus aureus and Pseudomonas aeruginosa were completely inhibited at a CA/SP@AgNs concentration of 20 mg/mL. The redox reaction of Ag+ with TA/Fe resulted in the oxidation of Fe2+ to Fe3+. The hemostatic ability of CA/SP@AgNs was significantly enhanced owing to the good coagulation ability of TA/Fe3+ in the blood, which reduced the bleeding time and hemostatic volume of the femoral artery to 109 s and 0.115 g, respectively. Therefore, TA/Fe-modified microspheres are good carriers of AgNs that can be used for efficient bacteriostasis, rapid hemostasis, and wound healing.

One-pot synthesis of gold-copper nanoparticles mediated by silk fibroin peptides: Peroxidase-like properties and its application in antioxidant detection

SFP@Au-CuNPs were synthesized by the one-pot reduction method using silk fibroin peptides as reductants and stabilizers. The synthesis process was simple, safe, and environmentally friendly. The synthesized SFP@Au-CuNPs showed effective peroxidase mimicking activity through colorimetric analysis and had a catalytic effect. The reaction pH value, temperature, time, and concentration were optimized to determine the best method for achieving the inherent catalytic activity in practical application. According to the double reciprocal curve, the Michaelis–Menten constants of TMB and H2O2 substrates were calculated to study the affinity of the SFP@Au-CuNPs using TMB and H2O2 substrates. The Km of H2O2 was 0.240 mM, and the TMB was 0.040 mM. SFP@Au-CuNPs had a strong affinity for the H2O2 and TMB substrates. The peroxidase-like characteristics of the SFP@Au-CuNPs were used to detect antioxidants, in which ascorbic acid LOD was 0.059 μM, gallic acid LOD was 0.010 μM, and LOD was 0.040 μM. Colorimetric analysis using UV-spectrophotometer was used to observe the color changes. The R2 values of the ascorbic acid, gallic acid, and l-cysteine were 0.998, 0.996, and 0.990, respectively, indicating that the curve has a good linear relationship in the detection range and the assay was successfully used to evaluate the antioxidant content of real fruits. This study provides a broader prospect for the preparation of nanozymes for relevant applications.

Calcium alginate/silk fibroin peptide/Bletilla striata polysaccharide blended microspheres loaded with tannic acid for rapid wound healing

Biodegradable natural polymers are receiving increasing attention as potential candidates for wound dressing. In the present study, composite microspheres (mCSB) based on calcium alginate (CA), silk fibroin peptide (SP), and Bletilla striata polysaccharide (BSP) were prepared by the reverse emulsion method. The excellent swelling properties of microspheres enable them to rapidly promote thrombosis. Microspheres can increase the platelet aggregation index to 1.5 and the aggregation rate of red blood cells to as high as 80 %. Furthermore, tannic acid (TA)-loaded microspheres demonstrate a slow-release effect on TA; this allows the microspheres to exhibit good long-lasting antibacterial properties. Due to the synergistic effects of SP and TA, the cell senescence was delayed, with a 126.69 % survival rate of fibroblasts after 3 days of incubation. In addition, TA led to a rapid reduction in inflammation levels, with a wound closure rate of >92.80 % within 7 days. The multifunctional TA-loaded mCSB has great application potential for rapid wound healing and the treatment of wound hemostasis.

Baicalein-loaded silk fibroin peptide nanofibers protect against cisplatin-induced acute kidney injury: Fabrication, characterization and mechanism

Silk fibroin (SF) is a natural polymeric biomaterial widely used in the preparation of drug delivery systems. Herein, silk fibroin peptide (SFP) was self-assembled into nanofibers, encapsulated a poorly water-soluble drug baicalein (SFP/BA NFs), and then used to protect against cisplatin-induced acute kidney injury (AKI). Specifically, the SFP/BA NFs significantly enhanced the aqueous dispersity, storage stability, and in vitro antioxidant activity of BA. SFP/BA NFs increased the drug uptake and localization to mitochondria. In vitro results demonstrated that SFP/BA NFs can relieve the cisplatin-induced HK-2 cell damage, and inhibit the cisplatin-induced accumulation of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) disruption. Mechanism studies demonstrated that SFP/BA NFs may exert nephroprotective effects by inhibiting both the cisplatin-induced DNA damage and the cGAS/STING pathway activation. In vivo results showed that cisplatin treatment resulted in decreased body weight, increased serum creatinine (SCr), and increased blood urea nitrogen (BUN) levels, while SFP/BA NFs reversed the above symptoms. Furthermore, SFP/BA NFs reversed the cisplatin-induced abnormal changes of antioxidant enzymes (e.g., SOD and GSH), and inhibited the cisplatin-induced DNA damage as well as the activation of cGAS/TING. Above all, our results revealed the potential of SFP/BA NFs to protect against cisplatin-induced AKI.

Engineering Natural and Recombinant Silks for Sustainable Biodevices.

Silk fibroin (SF) is a structural protein derived from natural silkworm silks. Materials fabricated based on SF usually inherit extraordinary physical and biological properties, including high mechanical strength, toughness, optical transparency, tailorable biodegradability, and biocompatibility. Therefore, SF has attracted interest in the development of sustainable biodevices, especially for emergent bio-electronic technologies. To expand the function of current silk devices, the SF characteristic sequence has been used to synthesize recombinant silk proteins that benefit from SF and other functional peptides, such as stimuli-responsive elastin peptides. In addition to genetic engineering methods, innovated chemistry modification approaches and improved material processing techniques have also been developed for fabricating advanced silk materials with tailored chemical features and nanostructures. Herein, this review summarizes various methods to synthesize functional silk-based materials from different perspectives. This review also highlights the recent advances in the applications of natural and recombinant silks in tissue regeneration, soft robotics, and biosensors, using B. mori SF and silk-elastin-like proteins (SELPs) as examples.

Injectable hydrogels based on silk fibroin peptide grafted hydroxypropyl chitosan and oxidized microcrystalline cellulose for scarless wound healing

Scars are consequences of the wound healing process, and eliminating scar formation remains a significant challenge. Here, an injectable HMSC hydrogel was developed based on silk fibroin peptide grafted hydroxypropyl chitosan (HPCS-g-SFP) and oxidized microcrystalline cellulose (OMCC) via Schiff base bonds. The synthesized HPCS-g-SFP copolymer displayed efficient free radical scavenging ability on hydrogen hydroxyl radicals and 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH). The pore size, gelling time, equilibrium swelling rate and water retention properties of HMSC hydrogel could be regulated by changing ratio of OMCC and HPCS-g-SFP. Then, tetramethylpyrazine (TMP) was encapsulated into HMSC hydrogel to obtain TMP-loaded HMSC hydrogel. The TMP-loaded HMSC hydrogel facilitated 95% cell activity retention after culturing with human skin fibroblasts (HSF) or human hypertrophic scar fibroblast (HSFB) cells for 24 h. Additionally, in vivo animal experiments confirmed that TMP-loaded HMSC hydrogel promoted rapid wound healing while preventing scar formation. The designed injectable TMP-loaded HMSC hydrogel has potentials in promoting scarless wound healing.

Enhanced physicochemical stabilities of cyanidin-3-O-glucoside via combination with silk fibroin peptide

Applications of cyanidin-3-O-glucoside (C3G) are limited due to the poor stabilities. In this work, we proposed using silk fibroin peptide (SFP) to bind with C3G and form nanocomposites (134.73 ± 4.51 nm) for stabilization. When interacted with C3G, the fluorescence of SFP contributed by tyrosine and phenylalanine amino acids was quenched, which was proved a static quenching with the β-sheet structure of SFP unchanged. With the further exploration of the physicochemical stabilities of C3G in the nanocomposites, we demonstrated that the tolerance of C3G to the alkaline environment and the retention ratio of C3G in various concentrations of metallic ion Cu2+ were significantly improved. In addition, the heat resistance of C3G in SFP at 80 °C was also enhanced with up to an increase of 2.5 times for the average half-life of C3G. Our results shed light on SFP could enhance physicochemical stabilities of C3G with maintaining its antioxidant activity.

Characterization of undegraded and degraded silk fibroin and its significant impact on the properties of the resulting silk biomaterials

The silk fibroin (SF) regeneration process significantly affects the resulting biomaterials, unfortunately, there has been insufficient study regarding the most suitable regeneration method for SF. In this study, we prepared undegraded SF (uSF) and degraded SF (dSF) by common regeneration methods and studied their difference in detail. The results demonstrated that the degradation degree of SF peptide chain had little influence on the secondary structure and thermal stability of SF materials. While, uSF solution showed higher viscosity and surface tension than dSF solution. The uSF membrane (uSFM) could be elongated approximately 134%, 1.6 times the degraded SF membrane (dSFM). SEM implied that both uSF and dSF existed in aqueous solution as micelles with a diameter of approximately 30 nm. dSF could directly form SF nanoparticles (dSFNPs) when poured into acetone while uSF could only form nanoparticles (uSFNP) with the addition of SDS. Glucose oxidase embedded into dSFM and dSFNP showed high catalytic activities, but uSFNP demonstrated nearly no activity. In addition, the dSFM was more appropriate for L929 cell culture. Considering the obvious difference between the two SF proteins, our results are significant in guiding the application of appropriate SF proteins in tissue engineering materials, bioactive materials, bioink, etc.

Dual-functional SFP/PAN based nano drug release system for treatment and nutrients

Nano drug delivery systems can control the ordered release of drugs. To achieve the target of supplying therapeutics and nutrients at the same time, a novel nano drug delivery system with a core–shell structure was prepared by coaxial electrospinning. Polyacrylonitrile (PAN) has been used to produce a drug release scaffold in the shell section, mixed with absorbable silk fibroin peptide (SFP) as a nutrient. Ciprofloxacin (CPFX), a broad-spectrum antibiotic, was used as the core, as well as an antibacterial agent. Owing to its low molecular weight, using a pure SFP thin solution to manufacture nanofibers by electrospinning is still technically challenging. Thus, different ratios of PAN to SFP were used in the shell electrospinning solution. In this research, a novel nano dual-functionality drug delivery system has been successfully prepared. In vitro testing demonstrated that nanofibers could supply more nutrients with increasing SFP in shell solutions; however, the ability to maintain controlled release was reduced. It was found that the nanofiber membrane had the best controlled drug release capability for a PAN-to-SFP mass ratio of 95:5. Overall, most ciprofloxacin was released in the first 12 h, while the release of SFP was constant throughout the first 24 h. Our modeling demonstrated that the release of CPFX and SFP is best described using a first-order kinetic model. The developed drug delivery system is designed to release antimicrobial drugs in a controlled manner and provide absorbable nutrients simultaneously.

Proteomics analysis of the soil textile imprints from tomb M6043 of the Dahekou Cemetery site in Yicheng County, Shanxi Province, China

Proteomics has made important contributions to identify protein residues from ancient burials, especially for those archeological remains that have severely degraded. These analysis methods make it possible to identify the raw materials of textile imprints found in archeological sites and allow the imprints to be a new archeological material that can compensate for the lack of evidence of early silk artifacts. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) in proteomics was used to analyze the textile imprints found in the tomb M6043 from the Dahekou Cemetery site (1046 BC–771 BC) in China. A combination of accurate mass and time (AMT) tags and peptide sequencing was used to identify the fiber type of the textile imprints. The AMT tag analysis results suggested that some organic residues from the archeological samples had a similar structure to the peptides in modern silk. Five different types of silk fibroin peptides determined that the archeological soil samples contained silk protein residues. Based on the proteomics analysis results, it can be determined that the raw material of the textile imprints from tomb M6043 of the Dahekou Cemetery site was silk fiber. Combining the location and the microtopography observation results of the textile imprints, it can be speculated that these imprints were probably residual traces of the pall, which were generally called “Huang Wei (荒帷)” in ancient China. This study shows that proteomics can play an important role in studying archeological protein residues, and textile soil imprints can be used as archeological materials for ancient textile research.

Brain Factor-7\xae improves learning and memory deficits and attenuates ischemic brain damage by reduction of ROS generation in stroke in vivo and in vitro

Brain Factor-7® (BF-7), silk fibroin peptide, is known to be effective in improvement of memory and learning ability. In this study, the effects of BF-7 (10 mg/kg, p.o., pre-treatment for 7 days and post-treatment for 7 days) on neuroprotection and memory and learning functions were investigated in a rat model of transient focal cerebral ischemia and a gerbil model of transient global forebrain ischemia. Furthermore, to find the mechanism of BF-7, we examined the neuroprotective and antioxidative effects of BF-7 in vitro using neuroblastoma (SH-SY5Y) cells. In vivo model, treatment with BF-7 significantly reduced the number of errors in 8-arm maze test and significantly increased latency time in passive avoidance test at 7 days after focal ischemia compared to those in the vehicle-treated group. In addition, treatment with BF-7 significantly decreased the infarct size or neuronal death at 7 day following transient ischemia compared to that in the vehicle-treated group. In vitro model, 10 or 20 μg/ml of BF-7 treatment significantly increased cell viability in dose-dependent manner. In addition, oxidative stress was significantly attenuated in the ischemic cells, showing that 10 or 20 μg/ml of BF-7 treatment significantly reduced the generation of reactive oxygen species (ROS) compared to that in the ischemic cells. These results indicate that BF-7 treatment can attenuate ischemic damages and improve memory deficits via reduction of ROS generation.

The protective effect of silk fibroin on high glucose induced insulin resistance in HepG2 cells

The therapeutic use of silk-derived materials such as fibroin in biomedicine is well-established in Southeast Asian countries. Studies indicated that silk fibroin (SF) peptide enhances insulin sensitivity and glucose metabolism phenomena associated with type 2 diabetes mellitus (T2DM) suggesting this peptide may be beneficial to treat this disease. However, the mechanisms underlying protective effect of SF in insulin-mediated hepatic metabolic dysfunction remains unclear. The aim of this study was to investigate the influence of SF on insulin resistant HepG2 cells which were used a model of T2DM. Treatment of cells with 30 mmol/L of glucose and 10−6 mol/L insulin for 48 h significantly reduced glucose consumptions and intracellular glycogen levels but increased triglyceride (TG) levels. SF or metformin alone elevated glucose consumptions and glycogen accumulation accompanied by lower TG content. Greater effects in these metabolic parameters were found when SF and metformin were combined. Treatment of insulin resistant cells with SF or metformin alone decreased levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF-α) and interleukin-6 (IL-6); whereas antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity, as well as total antioxidant capacity (T-AOC) ability increased. The combination of SF and metformin produced greater changes in these parameters compared to metformin alone. Data indicated that the protective effect of SF or metformin in insulin resistant HepG2 cells involves inhibition of oxidant processes and that the combination of agents may prove more effective therapeutically.

Silk fibroin peptide suppresses proliferation and induces apoptosis and cell cycle arrest in human lung cancer cells.

Silkworm cocoon was recorded to cure carbuncle in the Compendium of Materia Medica. Previous studies have demonstrated that the supplemental silk protein sericin exhibits anticancer activity. In the present study, we investigated the effects of silk fibroin peptide (SFP) extracted from silkworm cocoons against human lung cancer cells in vitro and in vivo and its possible anticancer mechanisms. SFP that we prepared had high content of glycine (~ 30%) and showed a molecular weight of ~ 10 kDa. Intragastric administration of SFP (30 g/kg/d) for 14 days did not affect the weights, vital signs, routine blood indices, and blood biochemical parameters in mice. MTT assay showed that SFP dose-dependently inhibited the growth of human lung cancer A549 and H460 cells in vitro with IC50 values of 9.921 and 9.083 mg/mL, respectively. SFP also dose-dependently suppressed the clonogenic activity of the two cell lines. In lung cancer H460 xenograft mice, intraperitoneal injection of SFP (200 or 500 mg/kg/d) for 40 days significantly suppressed the tumor growth, but did not induce significant changes in the body weight. We further examined the effects of SFP on cell cycle and apoptosis in H460 cells using flow cytometry, which revealed that SFP-induced cell cycle arrest at the S phase, and then promoted cell apoptosis. We demonstrated that SFP (20-50 mg/mL) dose-dependently downregulates Bcl-2 protein expression and upregulates Bax protein in H460 cells during cell apoptosis. The results suggest that SFP should be studied further as a novel therapeutic agent for the treatment of lung cancer.

Using of hydrated lime water as a novel degumming agent of silk and sericin recycling from wastewater

The aqueous solution of hydrated lime (calcium hydroxide) was first used as a silk-degumming/refining agent. The sericin outside silk fibroin filaments was completely removed after boiling (20 min × 2) in a 0.025% calcium hydroxide solution. The calcium hydroxide degumming did not induce an evident breakage of the silk fibroin peptide chains. The tensile, thermal and surface properties of the fibroin fibre all showed that it is a degumming agent slightly low to neutral soap and far superior to Na2CO3 solution. The alkaline degumming wastewater containing sericin was neutralized by sulphuric acid or phosphoric acid and generated insoluble calcium salt precipitation, which can be used as plant fertilizer. After the residual solution was concentrated and filtered, the sericin powder was obtained using a spray dryer or lyophilizer. The sericin with a lower molecular mass (≤20 kDa) can be widely used in such applications as cosmetics, medical biomaterials, food or medium additives. The hydrated lime water as a novel silk degumming agent can be used widely in the silk industry. The degumming technology not only avoids serious environmental pollution from degumming waste liquid, but also can recover a large number of biological resources-sericin protein.

Enzymatic synthesis of quaternary ammonium chitosan-silk fibroin peptide copolymer and its characterization

Free radicals are closely related to the occurrence and development of aging, cancer and inflammation. The aim of the present study was to improve the antioxidant effects of quaternary ammonium chitosan (QCS) by modified with silk fibroin peptide (SFP). The modification had been confirmed by FT-IR and 1H NMR spectroscopy. Degree of substitution (DS) of QCS-SFP could be controlled by adjusting the reaction conditions. In this paper, the results of moisture absorption and retention test showed that QCS-SFP had excellent moisture absorption and retention properties. In vitro antioxidant activity assays demonstrated that, with the DS and concentration increasing of QCS-SFP, the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, hydroxyl radical and hydrogen peroxide (H2O2) increased. Furthermore, the methyl thiazolyl tetrazolium assay (MTT) was applied to evaluate the biocompatibility of QCS-SFP, and the result indicated that QCS-SFP with the DS of 0.32 displayed pronounced cell viability at 100ppm. These results suggested that QCS-SFP would appear to be a promising candidate for wound dressing application.

Fabrication of Eu-doped Gd(OH)3 Nanorods with Enhanced Magnetic- Resonance and Luminescence Imaging

Multimodal bio-imaging is a new technique with more than one imaging modality. Eu3+ doping can tailor the multi-functions of Gd-based nanorods (NRs) to obtain the resolution the imaging at the cellular level. Silk fibroin with His and Lys can induce to fabricate metal compounds particles. However, one-step preparation of SFP-linked Eu-Gd(OH)3 NRs with cyto-compatibility is very challenging. Eu-doped Gd(OH)3 nanorods with silk fibroin peptides (SFP-NRs) are synthesized via a simple and feasible biomimetic method in the assistance of SFPs. The measurement results showed that these hexagonal crystal NRs possessed 300 nm of the length. Compared with pure NRs, SFP-NRs exhibited better in vitro T1 signal-enhancement of magnetic resonance (MR) imaging due to their higher ratio of Eu and Gd and SFP coating on their surface, and the longitudinal relaxivity r1 value is 2.57 (Gd mM·s)-1 under a 7.0 T MR imaging system. Furthermore, a series of in vivo T1-weighted MR images between pre- and post-injection in tumor regions for 9 h indicated that average intensity of post-injection of SF-NRs was enhanced to 68%, higher the increased value of pure NRs (19.6%), but also SFP-NRs showed the good luminescence labeling of viable cell in the fluorescence observation. These results indicate that Eu-doped SFP-NRs have potential as T1 MR imaging contrast agents and optical imaging probe in tumor-detection field.