Effect of Degumming in the Characteristics of Silk Fibroin Nanoparticles

Several studies have stated that the process used for sericin removal, or degumming, from silk cocoons has a strong impact on the silk fibroin integrity and consequently in their mechanical or biochemical properties after processing it into several biomaterials (e.g., fibers, films or scaffolds) but still, there is a lack of information of the impact on the features of silk nanoparticles. In this work, silk cocoons were degummed following four standard methods: autoclaving, short alkaline (Na2CO3) boiling, long alkaline (Na2CO3) boiling, and ultrasounds. The resultant silk fibroin fibers were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate and used for nanoparticle synthesis by rapid desolvation in polar organic solvents. The relative efficiencies of the degumming processes and the integrity of the resulting fibroin fibers obtained were analyzed by mass loss, optical microscopy, thermogravimetric analysis, infrared spectroscopy, and SDS-PAGE. Particle sizes and morphology were analyzed by Dynamic Light Scattering and Field Emission Scanning Electronic Microscopy. The results showed that the different treatments had a remarkable impact on the integrity of the silk fibroin chains, as confirmed by gel electrophoresis, which can be correlated with particle mean size and size distribution changes. The smallest nanoparticles (156 ± 3 nm) and the most negative Z potential (−30.2 ± 1.8 mV) were obtained with the combination of long treatment (2 h) of boiling in alkaline solution (Na2CO3 0.02 eq/L). The study confirms that parameters of the process, such as the composition of the solution and time of the degumming step, must be controlled in order to reach an optimum reproducibility of the nanoparticle production.This work has been partially supported (80%) by the European Commission ERDF/FEDER Operational Programme 'Murcia' CCI N° 2007ES161PO001 (Project No. 14-20/20), and the Spanish MINECO (Ref. CTQ2017-87708-R) and the programme of support to the research of the Seneca Foundation of Science and Technology of Murcia, Spain (Ref. 20977/PI/18). A.A.L.-P.’s research contract was partially supported (80%) by the ERDF/FEDER Operational Programme 'Murcia' CCI N° 2007ES161PO001 (Project No. 14-20/20),. M.G. Montalbán’s research contract is funded by the Spanish MINECO (Juan de la Cierva-Formación contract, Ref. FJCI-2016-28081). S.D.A.-C.’s research contract is funded by the program INIA-CCAA (DOC INIA 2015), announced by the National Institute for Agricultural and Food Research and Technology (INIA) and supported by the Spanish State Research Agency (AEI) under the Spanish Ministry of Economy, Industry and Competitiveness

Revealing the Influence of the Degumming Process in the Properties of Silk Fibroin Nanoparticles

Several studies have stated that the process used for sericin removal, or degumming, from silk cocoons has a strong impact in the silk fibroin integrity and consequently in their mechanical or biochemical properties after processing it into several biomaterials (e.g. fibers, films or scaffolds) but still, there is a lack of information of the impact on the features of silk nanoparticles. In this work, silk cocoons were degummed following four standard methods: autoclaving, short alkaline (Na2CO3) boiling, long alkaline (Na2CO3) boiling and ultrasounds. The resultant silk fibroin fibers were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate and used for nanoparticle synthesis by rapid desolvation in polar organic solvents. The relative efficiencies of the degumming processes and the integrity of the resulting fibroin fibers obtained were analyzed by mass loss, optical microscopy, thermogravimetric analysis, infrared spectroscopy and SDS-PAGE. Particle sizes and morphology were analyzed by Dynamic Light Scattering and Field Emission Scanning Electronic Microscopy. The results showed that the different treatments had a remarkable impact on the integrity of the silk fibroin chains, as confirmed by gel electrophoresis, which can be correlated with particle mean size and size distribution changes. The smallest nanoparticles (156 ± 3 nm) and the most negative Z potential (−30.2 ± 1.8 mV) were obtained with the combination of long treatment (2 h) of boiling in alkaline solution (Na2CO3 0.02 eq/L). The study confirms that parameters of the process, such as composition of the solution and time of the degumming step, must be controlled in order to reach an optimum reproducibility of the nanoparticle production.This work has been partially supported (80%) from the European Commission ERDF/FEDER Operational Programme 'Murcia' CCI N° 2007ES161PO001 (Project No. 14-20/20), and the Spanish MINECO (Ref. CTQ2017-87708-R) and the programme of support to the research of the Seneca Foundation of Science and Technology of Murcia, Spain (Ref. 20977/PI/18).A.A. Lozano-Pérez’s research contract was partially supported (80%) by the ERDF/FEDER Operational Programme 'Murcia' CCI N° 2007ES161PO001 (Project No. 14-20/20),. M.G. Montalbán’s research contract is funded by the Spanish MINECO (Juan de la Cierva-Formación contract, Ref. FJCI-2016-28081). S.D. Aznar-Cervantes’s research contract is funded by the program INIA-CCAA (DOC INIA 2015), announced by the National Institute for Agricultural and Food Research and Technology (INIA) and supported by The Spanish State Research Agency (AEI) under the Spanish Ministry of Economy, Industry and Competitiveness

Unexpected high toughness of Samia cynthia ricini silk gut

Silk gut fibers were produced from the silkworm Samia cynthia ricini silk glands by the usual procedure of immersion in a mildly acidic solution and subsequent stretching. The morphology of the silk guts was assessed by scanning electron microscopy, and their microstructure was assessed by infrared spectroscopy and X-ray diffraction. It was found that both naturally spun and Samia silk guts share a common semicrystalline microstructure. The mechanical characterization of the silk guts revealed that these fibers show an elastomeric behavior when tested in water, and exhibit a genuine ground state to which the fiber may revert independently of its previous loading history. In spite of its large cross-sectional area compared with naturally spun silk fibers, Samia silk guts show values of work to fracture up to 160 MJ m, much larger than those of most of their natural counterparts, and establish a new record value for this parameter in silk guts

Mechanical behaviour and formation process of silkworm silk gut

High performance silk fibers were produced directly from the silk glands of silkworms ("Bombyx mori") following an alternative route to natural spinning. This route is based on a traditional procedure that consists of soaking the silk glands in a vinegar solution and stretching them by hand leading to the so called silkworm guts. Here we present, to the authors’ best knowledge, the first comprehensive study on the formation, properties and microstructure of silkworm gut fibers. Comparison of the tensile properties and microstructural organization of the silkworm guts with those of naturally spun fibers allows gain of a deeper insight into the mechanisms that lead to the formation of the fiber, as well as the relationship between the microstructure and properties of these materials. In this regard, it is proved that an acidic environment and subsequent application of tensile stress in the range of 1000 kPa are sufficient conditions for the formation of a silk fiber

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Silkworm Gut Fibres from Silk Glands of Samia cynthia ricini&mdash;Potential Use as a Scaffold in Tissue Engineering

High-performance fibroin fibres are ideal candidates for the manufacture of scaffolds with applications in tissue engineering due to the excellent mechanical properties and optimal biocompatibility of this protein. In this work, the manufacture of high-strength fibres made from the silk glands of Samia cynthia ricini is explored. The glands were subjected to soaking in aqueous dissolutions of acetic acid and stretched to manufacture the fibres. The materials produced were widely characterized, in terms of morphology, mechanical properties, crystallinity and content of secondary structures, comparing them with those produced by the standard procedure published for Bombyx mori. In addition, mechanical properties and biocompatibility of a braided scaffold produced from these fibres was evaluated. The results obtained show that the fibres from B. mori present a higher degree of crystallinity than those from S. c. ricini, which is reflected in higher values of elastic modulus and lower values of strain at break. Moreover, a decrease in the elongation values of the fibres from S. c. ricini was observed as the concentration of acetic acid was increased during the manufacture. On the other hand, the study of the braided scaffolds showed higher values of tensile strength and strain at break in the case of S. c. ricini materials and similar values of elastic modulus, compared to those of B. mori, displaying both scaffolds optimal biocompatibility using a fibroblast cell line

Products of Sericulture and Their Hypoglycemic Action Evaluated by Using the Silkworm, Bombyx mori (Lepidoptera: Bombycidae), as a Model

Sericulture generates different natural products with potential medical applications. Silk peptides, worms, or even pupae are commonly employed in traditional Asian medicine with a wide variety of purposes, and some scientific work has been focused on their antidiabetic properties. This work evaluates the postprandial antihyperglycemic activity of fibroin, sericin, and powder made from either larvae or pupae of silkworms, and Bombyx mori L. (Lepidoptera: Bombycidae), employing the silkworm itself as an animal model. The results indicate a reduction in the glucose levels in hemolymph after sucrose or glucose-induced hyperglycemia when these products are included in the diet of the worms

Silk Fibroin Pads for Whole Blood Glucose Determination

In this work, we present a durable and miniaturized photonic lab on a chip (PhLOC) integrating functionalized silk fibroin pads for optical glucose quantification in whole blood samples. The PhLOC consists of a poly(methyl methacrylate) (PMMA) disposable structure for the pad holding and a coupling system for commercial optic fibers connection. The silk matrix, together with the PMMA design, has the capability to separate the plasma from the cell fraction of whole blood by plasma diffusion into the silk, minimizing the absorbance interferences from the hemoglobin of the erythrocytes. Then, the enzymes present in the matrix react with the glucose in the sample and produce a color change in an amplified process where the analyte&#8212;mediator&#8212;matrix interacts sequentially, increasing the common signal from the oxidized mediator (2 fold). The sensor works in the adequate linear range to distinguish between healthy and unhealthy glucose levels (0 to 12 mM), with a sensitivity of 0.084 a.u. mM&#8722;1, a limit of detection of 0.18 mM and a limit of quantification of 1.44 mM. Furthermore, durability of the sensor is remarkable, maintaining its response unchangeable during the first 7 months of tests

Fiber optic humidity sensor based on silk fibroin interference films

The article presents an inexpensive and simple method of fiber optic interference relative humidity (RH) sensors based on silk fibroin (SF) films. The sensors were made on standard multimode telecommunications optical fibers using dip-coating method and examined using broadband light sources. The measuring stand at which the basic sensor parameters were measured and the measured parameters were presented