| 1. |
- Singh, Manish, et al.
(författare)
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Conductive and enzyme-like silk fibers for soft sensing application
- 2020
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Ingår i: Biosensors and Bioelectronics. - : Elsevier BV. - 0956-5663. ; 150, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- A combination of supercritical carbon dioxide (scCO2) impregnation of pyrrole and sonochemical transformation of permanganate (KMnO4) was used to impart conductive and catalytic properties to silk fibers. The results indicated that the conductivity (from polypyrrole –PPy) and catalytic activities (from manganese dioxide –MnO2) were independent and complementary within the processing parameters used. The enhanced conductivity was attributed to scCO2 preferentially distributing the pyrrole monomers along with the silk internal fibrillar structure and hence, yielding a more linear PPy. The oxidative properties of the PPy-MnO2-silk hybrid showed an enzyme-like behavior for the degradation of hydrogen peroxide (H2O2) with a Km of about 13 mM and specific activity of 1470 ± 75 μmol/min/g. Finally, we demonstrated that the PPy-MnO2-silk hybrid could be used as soft working electrodes for the simultaneous degradation and detection of H2O2.
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| 2. |
- Singh, Manish, et al.
(författare)
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Manganese oxide functionalized silk fibers for enzyme mimics application
- 2020
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Ingår i: Reactive and Functional Polymers. - : Elsevier BV. - 1381-5148.
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Tidskriftsartikel (refereegranskat)abstract
- The inorganic metal or metal-oxide nanoparticles (NPs) that mimic enzymes are of great interest due to improved physical and chemical properties compared with native enzymes. Here, we report that manganese dioxide (MnO2)-Silk exhibit catalase, oxidase, and peroxidase-like activities. The MnO2-Silk hybrid fibers effectively decomposed hydrogen peroxide (H2O2) and oxidized the typical horseradish peroxidase substrates, such as o-phenylenediamine (OPD), and 3,3′,5,5′- tetramethylbenzidine (TMB) in the presence or absence of H2O2. The oxidative properties of MnO2-Silk fiber hybrid showed an enzyme-like behavior for the catalase-like activity, oxidase-like activity, and peroxidase-like activity. The operational stability of the MnO2-Silk fiber hybrid over ten cycles showed a constant residual activity of about 25–30% after 2–3 cycles indicating that MnO2-Silk fiber hybrid could be used as a satisfactory oxidoreductase enzyme mimics. Potentiometric titration was used to determine the surface charges of the MnO2-Silk catalyst. Together, we identified the reactive species as Mn1−x4+Mnx3+O2−x(OH)x with a pK of approximately 5.2. Our results have implications on the understanding of the catalytic origin and interaction of metal oxides NP with various biomaterials.
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| 3. |
- Singh, Manish, et al.
(författare)
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Sonication enhances the stability of MnO2 nanoparticles on silk film template for enzyme mimic application
- 2020
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Ingår i: Ultrasonics Sonochemistry. - : Elsevier BV. - 1350-4177. ; 64
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an in-situ method using sonication (3 mm probe sonicator, 30 W, 20 kHz) and auto-reduction (control) to study the mechanism of the formation of manganese dioxide (MnO2) on a solid template (silk film), and its resulting enzymatic activity on tetramethylbenzidine (TMB) substrate. The fabrication of the silk film was first optimized for stability (no degradation) and optical transparency. A factorial approach was used to assess the effect of sonication time and the initial concentration of potassium permanganate (KMnO4). The result indicated a significant correlation with a fraction of KMnO4 consumed and MnO2 formation. Further, we found that the optimal process conditions to obtain a stable silk film with highly catalytic MnO2 nanoparticles (NPs) was 30 min of sonication in the presence of 0.5 mM of KMnO4 at a temperature of 20–24 °C. Under the optimal condition, we monitored in-situ the formation of MnO2 on the silk film, and after thorough rinsing, the in-situ catalysis of 0.8 mM of TMB substrate. For control, we used the auto-reduction of KMnO4 onto the silk film after about 16 h. The result from single-wavelength analysis confirmed the different kinetics rates for the formation of MnO2 via sonication and auto-reduction. The result from the multivariate component analysis indicated a three components route for sonication and auto-reduction to form MnO2-Silk. Overall, we found that the smaller size, more mono-dispersed, and deeper buried MnO2 NPs in silk film prepared by sonication, conferred a higher catalytic activity and stability to the hybrid material.
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| 4. |
- Singh, Manish, et al.
(författare)
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Supercritical carbon dioxide impregnation of gold nanoparticles demonstrates a new route for the fabrication of hybrid silk materials
- 2022
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Ingår i: Insects. - : MDPI AG. - 2075-4450. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- How many nanoparticles can we load in a fiber? How much will leak? Underlying is the relatively new question of the “space available” in fibers for nanoparticle loading. Here, using supercritical carbon dioxide (scCO2 ) as a carrier fluid, we explored the impregnation in four Indian silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold nanoparticles (5, 20, 50, 100 and 150 nm in diameter). All silks could be permanently impregnated with nanoparticles up to 150 nm in size under scCO2 impregnation. Accompanying structural changes indicated that the amorphous silk domains reorganized to accommodate the gold NPs. The mechanism was studied in detail in degummed Mulberry silk fibers (i.e., without the sericin coating) with the 5 nm nanoparticle. The combined effects of concentration, time of impregnation, scCO2 pressure, and temperature showed that only a narrow set of conditions allowed for permanent impregnation without deterioration of the properties of the silk fibers.
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