Cellulose acetate/multi-wall carbon nanotube/Ag nanofiber composite for antibacterial applications.

Herein we propose cellulose acetate/carbon nanotube/silver nanoparticles (CA/CNT/Ag) nanofiber composite for antibacterial applications. The nanofiber composite are expected to avoid harmful effects of silver (i.e. argyria and argyrosis) owing to anchoring of silver nanoparticles on carbon nanotubes (CNTs) and embedding of the composite inside cellulose acetate (CA) matrix. The carbon nanotubes/silver nanoparticles (CNT/Ag) nanocomposite localized inside the CA polymer matrix allow minimal/no direct contact of silver nanoparticles with human cells and are expected to show reduced silver leaching. The cellulose acetate (CA) nanofibers loaded with silver nanoparticles anchored multiwall carbon nanotubes (CNT/Ag) were fabricated by electrospinning. The samples were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), tensile strength tests and antibacterial assays. Synthesis of the CNT/Ag nanocomposite was confirmed with XPS, XRD, EDS and TEM analysis. SEM images showed regular morphology of the CA/CNT/Ag nanofiber composites. TEM images depicted anchoring of silver nanoparticles on CNTs and embedding of CNT/Ag in the CA nanofiber matrix. The antibacterial test results demonstrated excellent antibacterial performance of the CA/CNT/Ag. The CA/CNT/Ag samples ensured effective bacterial growth inhibition on agar plates, in liquid medium (optical density, OD590nm) (for 48 h) and in bactericidal assay (relative cell viability, %). Our results suggested CA/CNT/Ag composite nanofibers as potential candidate for safer antibacterial applications.

Characterizations and application of CA/ZnO/AgNP composite nanofibers for sustained antibacterial properties.

Although silver based nanofibers possess excellent bactericidal and bacteriostatic characteristics. However, excess release/contact with silver may induce harmful side-effects including carcinoma, argyria, argyrosis and allergies. Similarly, silver depletion may limit prolonged antibacterial activities as well. Thus present research proposes electrospun CA/ZnO/AgNPs composite nanofibers for biologically safer and sustained antibacterial applications. The ZnO/AgNPs were synthesized using dopamine hydrochloride (Dopa) as reducing agent to immobilize AgNPs on ZnO nanoparticles. A simple solution-mixing procedure effectively generated AgNPs on ZnO nanoparticles. Strong adhesive characteristics of Dopa initiate adsorption of silver ions on ZnO nanoparticle surfaces and its metal ion reducing properties generate AgNPs. Additionally, the Dopa mediation generates strongly adhered AgNPs. The ZnO/AgNPs were used to fabricate CA/ZnO/AgNPs nanofibers. Characterization techniques, XRD, XPS, TEM, FTIR and SEM confirmed synthesis of nanocomposites. Crystallite sizes of ZnO and AgNPs calculated by Debye-Scherrer equation were 17.85 nm and 11.68 nm respectively. Antibacterial assays confirmed CA/ZnO/AgNP's effectiveness in growth inhibition of E. coli and S. aureus strains on agar plate and in liquid medium. The nanofiber composites demonstrated 100% bactericidal properties against both the test strains. Bacterial growth inhibition in LB medium for 108 h indicated suitability of CA/ZnO/AgNPs composite nanofibers in sustained antibacterial applications such as antibacterial wound dressings and other applications demanding sustained antimicrobial properties.

A comparative study on synthesis of AgNPs on cellulose nanofibers by thermal treatment and DMF for antibacterial activities.

Herein we present our research on generation of silver nanoparticles (AgNPs) on cellulose nanofibers by thermal treatment and DMF as reducing agents. The cellulose (CE) nanofibers were prepared by deacetylation of electrospun cellulose acetate (CA) nanofibers which were subsequently silver coated using AgNO3 followed by thermal and DMF induced reduction processes. The samples were characterized with scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and antibacterial assays. Effect of these methods on mechanical properties, thermal stabilities (DTA analysis) and swelling of the CE nanofibers were also studied. Both the processes were effective and efficient in generation of AgNPs on CE nanofibers with higher contents and very good spatial distributions. The XRD, XPS and TEM results evidenced formation metallic AgNPs. TEM images depicted the CE nanofibers highly decorated with spherical AgNPs. The DMF induced process generated AgNPs with comparatively larger sizes. The antibacterial results confirmed excellent antibacterial performance of the CEAgNPs against S. aureus and E. coli. The CEAgNP nanofibers well decorated with AgNPs having good spatial distribution and excellent antibacterial performance suggests CEAgNPs as promising candidate for efficient antimicrobial activities.

Cellulose acetate nanofibers embedded with AgNPs anchored TiO2 nanoparticles for long term excellent antibacterial applications.

Silver nanoparticles (AgNPs) are effective antimicrobial agents however excess release of silver causes argyria and argyrosis. An strategy to avoid these detrimental side effects is immobilization of AgNPs on several organic and inorganic substrates. Herein, we propose immobilization of AgNPs on TiO2 nanoparticles by an environmentally green process subsequently incorporating the TiO2/AgNP into cellulose acetate (CA) nanofiber matrix. The TiO2/AgNP nanocomposite particles were prepared by coating TiO2 nanoparticles with polydopamine hydrochloride followed by a treatment in AgNO3 solution. Subsequently, the TiO2/AgNP nanocomposites were added into CA solution and electrospun to fabricate CA/TiO2/AgNP composite nanofibers. The samples were characterized by XRD, TEM, XPS, SEM, EDX, FTIR and antibacterial assays. Synthesis of TiO2/AgNP and its loading into CA nanofibers was confirmed by XRD, XPS, TEM and EDX analysis. SEM images indicated regular morphology of the nanofibers. The antibacterial test results confirmed CA/TiO2/AgNP composite nanofibers having excellent antibacterial performances for 36 h and substantial bacterial growth inhibition for 72 h.

Sonication induced effective approach for coloration of compact polyacrylonitrile (PAN) nanofibers.

We present our research on dyeability of polyacrylonitrile (PAN) nanofibers following ultrasonic dyeing method. Although PAN has been extensively utilized in textile apparel, sportswear, upholstery and home furnishing, however, coloration of PAN nanofibers has not yet been reported. PAN is a compact fiber while the nanofiber structure makes it more difficult to color PAN nanofibers. PAN is generally dyed with basic dyes and dyeing is carried out in acidic conditions, while the dyeing process takes about two hours at boiling temperature. A systematic study on dyeability of PAN nanofibers will extend its use in textile apparel industry. Thus, we used ultrasonic energy and first time conducted our research on dyeability of electrospun PAN nanofibers using disperse dyes. Dyeing process parameters such as dyeing time, temperatures and concentrations of dyes were optimized. Ultrasonic dyeing of PAN nanofibers was compared with its conventional dyeing as well. Affect of ultrasonic dyeing on the morphology, chemical state, crystallographic structure and mechanical strength of PAN nanofibers has been studied. PAN nanofiber samples were characterized by SEM, FTIR, XRD and tensile strength tests. The results revealed 80 °C and 60 min as optimum temperature and time for ultrasonic dyeing of PAN nanofibers. The ultrasonic dyeing does not affect morphology, chemical and crystalline structure of the PAN nanofibers while it improves their mechanical strength. Our research suggests dyeability of PAN nanofibers with disperse dyes by ultrasonic method and their subsequent use in textile apparels.

Antibacterial efficacy of poly(vinyl alcohol) composite nanofibers embedded with silver-anchored silica nanoparticles.

Silver has been widely used as an effective antibacterial agent especially for treating burns and wounds. However, release of silver from materials often arouse side effects due to toxicity of silver towards mammalian cells. Argyria and argyrosis are well known problems of acute toxicity of silver towards human body. Immobilization of silver is an effective approach to reduce silver release. Herein, we present poly(vinyl alcohol) (PVA) composite nanofibers embedded with silver-anchored silica nanoparticles (SSNs) as a novel antibacterial material. Silver nanoparticles anchored on silica nanoparticles were prepared and incorporated into PVA nanofibers to fabricate silver-silica embedded PVA nanofibers (SSN-PVA) by electrospinning. Incorporation of SSNs into PVA was confirmed by TEM and SEM results revealed regular nanofibers whose diameter increased with successive addition of SSNs. The SSN-PVA nanofibers showed significant antibacterial efficacy against both Gram-negative and Gram-positive bacteria. Our research results demonstrated SSN-embedded polymeric nanofibers can open up a promising prospect for the prevention of bacterial infection in diverse biomedical fields including wound dressing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1121-1128, 2018.

Ultrasonic-assisted dyeing of Nylon-6 nanofibers.

We first time report ultrasonic dyeing of the Nylon 6 nanofibers with two disperse dyes CI Disperse blue 56 and CI Disperse Red 167:1 by utilising ultrasonic energy during dyeing process. The Nylon 6 nanofibers were fabricated via electrospinning and dyed via batchwise method with and without sonication. Results revealed that ultrasonic dyeing produce higher color yield (K/S values) and substantially reduces dyeing time from 60min for conventional dyeing to 30min can be attributed to breakage of dye aggregate, transient cavitation near nanofiber surface and mass transfer within/between nanofibers. Color fastness results exhibited good to very good dye fixation. SEM images exhibit insignificant effect of sonication on morphology of the nanofibers. Our research results demonstrate ultrasonic dyeing as a better dyeing technique for Nylon 6 nanofibers with higher color yield and substantially reduced dyeing time.

Ultrasonic-assisted deacetylation of cellulose acetate nanofibers: A rapid method to produce cellulose nanofibers.

Herein we report a rapid method for deacetylation of cellulose acetate (CA) nanofibers in order to produce cellulose nanofibers using ultrasonic energy. The CA nanofibers were fabricated via electrospinning thereby treated with NaOH and NaOH/EtOH solutions at various pH levels for 30, 60 and 90min assisted by ultrasonic energy. The nanofiber webs were optimized by degree of deacetylation (DD%) and wicking behavior. The resultant nanofibers were further characterized by FTIR, SEM, WAXD, DSC analysis. The DD% and FTIR results confirmed a complete conversion of CA nanofibers to cellulose nanofibers within 1h with substantial increase of wicking height. Nanofibers morphology under SEM showed slightly swelling and no damage of nanofibers observed by use of ultrasonic energy. The results of ultrasonic-assisted deacetylation are comparable with the conventional deacetylation. Our rapid method offers substantially reduced deacetylation time from 30h to just 1h, thanks to the ultrasonic energy.

Silver coated anionic cellulose nanofiber composites for an efficient antimicrobial activity.

Herein, we report a comparative study of silver coated anionic cellulose nanocomposite before (CMC-Ag) and after (AgNPs/CMC) chemical reduction for antibacterial activity. Cellulose nanofibers were prepared by deacetylation of electrospun cellulose acetate nanofibers, which were then treated with sodium chloroacetate to prepare anionic cellulose nanofibers (CMC). Aqueous AgNO3 solution with different concentrations was employed to produce nanofiber composites. To obtain AgNPs/CMC, the resultant Ag/CMC nanofibers were chemically reduced with NaBH4. The nanocomposites were characterized by FE-SEM, FTIR, XPS and SEM-EDS. Antimicrobiality tests were conducted using S. aureus and Escherichia coli bacteria following standard test method JIS L1902, 2008. The EDS results confirmed higher silver content in CMC-Ag nanofibers than AgNPs/CMC nanofibers. The antimicrobial test and EDS results demonstrated higher silver release (larger halo width) by the former in comparison to later which confers better antimicrobiality by CMC-Ag nanofibers.

Ultrasonic dyeing of cellulose nanofibers.

Textile dyeing assisted by ultrasonic energy has attained a greater interest in recent years. We report ultrasonic dyeing of nanofibers for the very first time. We chose cellulose nanofibers and dyed with two reactive dyes, CI reactive black 5 and CI reactive red 195. The cellulose nanofibers were prepared by electrospinning of cellulose acetate (CA) followed by deacetylation. The FTIR results confirmed complete conversion of CA into cellulose nanofibers. Dyeing parameters optimized were dyeing temperature, dyeing time and dye concentrations for each class of the dye used. Results revealed that the ultrasonic dyeing produced higher color yield (K/S values) than the conventional dyeing. The color fastness test results depicted good dye fixation. SEM analysis evidenced that ultrasonic energy during dyeing do not affect surface morphology of nanofibers. The results conclude successful dyeing of cellulose nanofibers using ultrasonic energy with better color yield and color fastness results than conventional dyeing.