Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2022 Feb 22;7(9):7706–7714. doi: 10.1021/acsomega.1c06463

Cross-Linking of Centrifugally Spun Starch/Polyvinyl Alcohol (ST/PVA) Composite Ultrafine Fibers and Antibacterial Activity Loaded with Ag Nanoparticles

Xianglong Li 1, Yongna Zhang 1, Weicai Kong 1, Jing Zhou 1, Teng Hou 1, Xianggui Zhang 1, Lele Zhou 1, Mingbo Sun 1, Shu Liu 1, Bin Yang 1,*
PMCID: PMC8908533  PMID: 35284769

Abstract

graphic file with name ao1c06463_0010.jpg

In this research, centrifugally spun ultrafine composite starch/polyvinyl alcohol (ST/PVA) fibers with high water stability were prepared by cross-linking with a mixture of glutaraldehyde and formic acid in the form of vapor phase. The effect of cross-linking temperature combined with time on the water stability, crystal structure, and thermal properties of fibers was investigated to obtain the optimum parameters. On this basis, we further prepared Ag-loaded ST/PVA fibers with different contents of nano silver. The structure and properties of Ag-loaded fibers, which cross-linked under the optimum parameters, were analyzed. As a result, the Ag-loaded fibers exhibited excellent water stability and mechanical properties and possessed inhibition zone diameters of 3 and 2 mm to Escherichia coli and Staphylococcus. aureus, respectively. The antibacterial property of the Ag-loaded ST/PVA fibers provided a new route for developing less costly antibacterial fiber materials in the future.

1. Introduction

Biodegradable fibers are useful materials that have been widely used in many applications such as biomedicine, filtration, and food packaging.1 Nowadays, researchers mainly focus on fabricating fibers from cellulose, protein, polylactic acid (PLA), polyvinyl alcohol (PVA), polycaprolactone (PCL), etc.2 Among these, micro/nanofibers expressed superior properties such as mechanical properties, cell proliferation efficiency, filtration efficiency, antibacterial efficiency, etc.3 Centrifugal spinning, as one of the most important methods for preparing micro/nanofibers, has received great attention over the past few decades due to the advantages of no polar requirement for spinning solution/melt, high productivity of fibers, and ease of controlling the fluffy degree of fibrous membranes and engineering.4 Last century, the method originated from the cotton candy machine and was mainly used for preparing metallic glass fibers,5 mineral fibers,6 and functional fibers.7 However, the development of centrifugal spinning was greatly limited because of chemical fiber spinning, melting spinning, spunbond, and wet/dry spinning showing higher productivity and convenient assembly in preparing microfibers.8 In the beginning of this century, centrifugal spinning received great attention once again due to the capability for higher productivity of micro/nanofibers.4a,9 In early 2014, a research group from the USA together with the FibeRio Technology Corporation developed an engineered spinning line with a product of 12,000 g/h and fiber membrane width of 2.2 m.10 Nowadays, researchers from dozens of countries have concentrated on the centrifugally spun micro/nanofibers from polymers11 and inorganic metal oxides.12 These fibers showed higher mechanical properties, cell proliferation efficiency, filtration efficiency, and antibacterial efficiency and therefore presented great potential applications in tissue engineering, filtration, and antibacterial textiles.13

Our group concentrated on the development of ultrafine fibers using centrifugal spinning at the beginning of 2013. We now have successfully developed the setups of electric-assisted centrifugal spinning, air-assisted centrifugal spinning, and melting centrifugal spinning.14 By using these setups, we not only prepared ultrafine fibers from polyester (PET),15 polyvinylpyrrolidone (PVP),16 polyoxyethylene (PEO),13 and regenerated silk17 but also created highly porous ethyl cellulose fibers,18 alginate-rich nanofibers,19 and grape-tree-like and porous PTFE fibers.20 These fibers expressed high specific surface area, excellent solution absorption, and super-hydrophobic properties and are therefore particularly suitable for application in filtration, wound dressing, and oil/water separation. We also successfully developed centrifugally spun starch-based ultrafine fibers from amylopectin-rich starches with environmentally friendly sodium hydroxide solution as solvent.21 The parameter studies further revealed that the amylopectin ratios of starch suitable for fiber preparation could reach up to 81%,22 which means that centrifugal spinning is particularly suitable for starch-based ultrafine fibers from native starches (amylopectin ratio: 70–80%) and many modified starches. As a comparison, the electrospun starch ultrafine fibers were mainly prepared from modified starches by using dimethyl sulfoxide (DMSO) and formic acid as solvent,23 and the spinning process was not environmentally friendly.

Benefiting from the superior biocompatibility of starches, the ultrafine starch fibers presented a great potential application in drug delivery, antibacteria treatment, and tissue engineering.24 However, the large amount of hydrogen bond in starch molecular chains and the amorphous structure resulted in both electrospun and centrifugally spun starch fibers rapid dissolving in water25 and greatly limited the fiber application. Researchers usually attempted to improve the water stability of electrospun starch fiber by using glutaraldehyde as a cross-linker. Wang et al. prepared the starch fiber from starches with amylopectin 30% and cross-linked fiber by glutaraldehyde.26 They demonstrated that the water satiability of fibers greatly improved and the cross-linked fibers expressed excellent antibacterial properties. The obtained centrifugally spun starch fibers also showed rapid dissolution in water, but the water stability of fibers could not be improved by only using glutaraldehyde as solvent. The reason was that both the hydrogen bond and residual sodium hydroxide in fibers induced the rapid dissolving of fiber in water, while the residual sodium hydroxide in fibers did not react with glutaraldehyde. On this basis, we investigated a method for improving the fiber’s water stability by using citric acid/ethanol solution as cross-linker.25b The result showed that citric acid could efficiently improve the water stability of starch fibers, while the cross-linking temperature was required to be high at 165 °C. We also attempted to cross-link obtained fibers by acetic acid/glutaraldehyde at a temperature of 40 °C.27 As a result, the water stability of fibers could be improved, but the water stability of cross-linked fibers was still low.

In the previous report, we found that the PVA could effectively improve the mechanical property of starch fibers and the obtained ST/PVA fibrous membranes show great potential application in disposable nonwoven fabrics.14c In this work, we aimed to further broaden the application of ST/PVA fibers by improving the water stability. For this purpose, the cross-linker composed of glutaraldehyde/formic acid was used for cross-linking fibers in the form of vapor phase by controlling the temperature and time. Additionally, we also prepared Ag-loaded ST/PVA fibers and the antibacterial properties were studied.

2. Results and Discussion

2.1. Cross-Linking of ST/PVA Fibers

As we have widely demonstrated, centrifugal spinning is especially suitable for the ultrafine fiber preparation from native starches.21,27 However, the low tensile strength and water stability of pure starch fibers, due to of the highly branched amylopectin and large amount of hydroxyl, greatly limited the applications. In our previous paper, we provided a route for improving the tensile strength of pure starch fibers by adding PVA and the tensile strength was improved over 3 times than pure starch fibers, although the problem of low water stability of fibers was still not improved.14c On this basis, we prepared the ST/PVA fiber from a solution with a starch/PVA mass ratio of 60/40 by using the centrifugal spinning setup designed by our group (Figure 1), and the spinning solution was obtained by blending a starch solution of 12% (w/w) and a PVA solution of 8% (w/w) with a mass ratio of 50/50 according to our previous report.14c Then, we cross-linked fibers in the form of vapor phase with glutaraldehyde/formic acid as cross-linker to improve the water stability of fibers by controlling the temperature and time. The cross-linking mechanism was based on two reactions of acid–base neutralization between NaOH and formic acid and etherification between PVA and glutaraldehyde.28

Figure 1.

Figure 1

Open in a new tab

Schematic of the preparation of centrifugally spun ST/PVA fibers.

The morphology combined with the fiber diameter distribution of the cross-linked fibers is shown in Figure 2. From Figure 2a1–e1, we could observe that the color of fibrous membranes gradually tended to change from white to yellow with the cross-linking temperature increasing from 60 to 140 °C combined with time decreasing from 10 to 2 h (Table 1). The reason was probably due to the oxidation of starch during the cross-linking process.29 As could be obtained from Figure 2a2,4–e2,4, all of the cross-linked fibrous membranes expressed a well morphology and fiber diameter distributions showed no obvious change with cross-linking conditions. When the cross-linked fibers were immersed in water for 12 h, the fibers showed a swell in diameters but the degree of swelling decreased with the increase in cross-linking temperature, which indicated that the water stability was greatly improved (Figure 2a3,4–e3,4). Specifically, the fibers cross-linked at 60 °C for 10 h were almost dissolved after immersing in water for 12 h, which suggested that the fibers did not form the cross-linked structures at the condition. The results also suggested that the temperature was the main parameter affecting the degree of cross-linking of fibers. Additionally, it should be noted that although the fibers cross-linked at 140 °C for 2 h expressed high water stability, the more serious oxidation of fibers made the fibrous membrane show slight brittleness. Therefore, although the water stability of cross-liked fibers could be further improved by increasing the cross-linking temperature, the brittleness of the obtained fibrous membranes would depict a limit to their applications. As a result, the optimum parameter for cross-linking ST/PVA fibers was concluded to be 120 °C for 4 h. As a comparison, we also treated the as-spun ST/PVA fibers at 140 °C for 2 h without a cross-linker. As could be observed from Figure 2f1–, the treated fibers kept well fiber morphology same with as-spun fibers but would dissolve in water. Thus, the improvements in the water stability of ST/PVA fibers were completely attributed to the cross-linker.

Figure 2.

Figure 2

Open in a new tab

Photos of fibrous membranes, SEM images, and diameter distributions of ST/PVA fibers cross-linked at 60 °C for 10 h (a), 80 °C for 8 h (b), 100 °C for 6 h (c), 120 °C for 4 h (d), and 140 °C for 2 h (e) and treated at 140 °C for 2 h without a cross-linker (f).

Table 1. Cross-Linking Parameters.

volume ratio of formic acid/glutaraldehyde (v/v) cross-linking temperature (°C) cross-linking time (h)
4/1 60 10
80 8
100 6
120 4
140 2
Open in a new tab

2.2. Structure Analysis

Figure 3 shows the chemical structures of cross-linked fibers measured by FTIR and XRD. As we demonstrated in a previous paper, the starch and PVA powders were not reacted during the fiber preparation process and a new peak appeared at 1583 cm–1 for ST/PVA belonging to water molecules absorbed in the amorphous structure of starch.30 In this work, the peak appeared at 1585 cm–1 and was more obvious for the fibers cross-linked at temperatures of 120 and 140 °C. The cross-linking included two different reactions of neutralization reaction between sodium hydroxide and formic acid and aldolization between PVA and glutaraldehyde.31 Both of the reactions generated the water molecules continuously and increased with the improvement of cross-linking degree. Therefore, the fibers cross-linked at temperatures of 120 and 140 °C generated more water molecules. In this process, most of the generated water molecules were removed continuously due to the high cross-linking temperature. However, the remaining water molecules and reabsorbed water molecules due to the high hydrophilicity of cross-linked fibers still presented a peak at 1585 cm–1 (Figure 3a). For the thermally treated fibers, the water molecules were greatly removed, and therefore, no peak appeared at 1585 cm–1.

Figure 3.

Figure 3

Open in a new tab

Chemical structure of ST/PVA fibers: (a) XRD spectra and (b) FTIR spectra.

As we have reported, the ST/PVA fibers presented an amorphous structure due to the semicrystalline structure of starch and PVA being destroyed during the dissolving process.14c Similar results were obtained in this work for the fibers cross-linked below 100 °C that also showed amorphous structures (Figure 3b). The peak at 2θ of 19.7° tended to be sharper with further increasing the cross-linking temperature up to 120 and 140 °C. This peak belonged to the amorphous phase of PVA and was stronger than the crystalline peaks at 2θ of 19.4 and 20.2°.32 As has been widely demonstrated, starch retrogradation induced the molecular chain to rearrange into order and increased with the increasing of temperature.33 Thus, the increasing of peaks was probably due to more molecular chains rearranged into order during the cross-linking process at high-temperature conditions. More importantly, the thermal treatment of as-spun fibers without a cross-linker presented a new peak at 2θ of 11.2°, which further demonstrated the increasing of peaks attributed to the starch retrogradation.

2.3. Effects of PVA Ratios on the Structure of Obtained Fibers

Figure 4 presents the thermogravimetry (TG) and differential thermogravimetry (DTG) curves for the fibers cross-linked at different conditions and thermally treated without a cross-linker. All cross-linked samples expressed two main stages of thermal degradation (Figure 4a–e). The parameters that characterize the thermal decomposition are as follows: Tpeak is the temperature at which the degradation rate is maximum, and W is the weight loss. The first Tpeak was attributed to water molecular evaporation in fibers, and results in Table 2 demonstrated that the water in fibers range between 13.72 and 16.46% (w/w). The second Tpeak was attributed to the thermal decomposition of starch and the dehydration of hydroxyl groups at a low temperature of PVA.34 For the thermally treated fibers without a cross-linker (Figure 4f), the most obvious difference was that weight loss at the first Tpeak was lower than that of all cross-linked fibers (Table 2). The reason was due to the fact that thermal treatment greatly removed water molecules in fibers. It was also indicated that part of the water molecules in cross-linked fibers was attributed to the cross-linking process, which further verified the results of FTIR. In addition, the third inconspicuous stage of thermal degradation for all samples that appeared at above 350 °C probably belonged to the chain-scission at the high temperature of remaining PVA.34

Figure 4.

Figure 4

Open in a new tab

TG and DTG curves of ST/PVA fibers cross-linked at 60 °C for 10 h (a), 80 °C for 8 h (b), 100 °C for 6 h (c), 120 °C for 4 h (d), and 140 °C for 2 h (e) and treated at 140 °C for 2 h without a cross-linker (f).

Table 2. Thermal Parameters of Cross-Linked Fibers.

cross-linking conditions Tpeak (°C) W % (w/w)
60 °C/10 h 51.19 15.57
247.38 63.66
80 °C/80 h 53.70 13.98
240.57 58.90
100 °C/6 h 52.87 16.46
254.43 64.61
120 °C/4 h 52.88 14.32
255.45 64.89
140 °C/2 h 52.03 13.72
267.06 65.26
140 °C/2 h (without cross-linker) 72.25 7.58
270.37 65.41
Open in a new tab

As could be observed from Table 2, the temperature tended to slightly increase with the increase in cross-linking temperature. The results were consistent with the XRD results that cross-linking at higher temperatures would induce more molecular chains of starch to rearrange into order, and therefore improve the thermal stability of fibers. Even so, thermal decomposition temperatures of fibers were below those of starch and PVA powders, as have been provided in our previous paper.14c The weight losses during thermal decomposition for the cross-linked fibers and thermally treated fibers showed no obvious variation, which reflected that the effect of cross-linking on fibers’ thermal properties was fairly limited.

2.4. Ag-Loaded Fiber Preparation

Nano silver was added directly into the ST/PVA composite solution with a mass ratio of 15, 20, and 25% and then used for fiber preparation by using the centrifugal spinning setup made by our group.14c The obtained fibers were further cross-linked at a temperature 120 °C for 4 h. The morphology, diameter distributions, and EDS of the cross-linked Ag-loaded fibers are presented in Figure 5. We could observe from Figure 4a1–c1 that fibers showed a relatively smooth surface. The beaded free fibers were obtained from composite solutions with different nano silver contents, which suggested the excellent spinnability of the solution in the centrifugal spinning system (Figure 5a2–c2). The obtained fibers also depicted a relatively narrow diameter distribution with different nano silver contents and kept almost constant with pure ST/PVA fibers (Figure 5a3–c3). Additionally, the atom content of nano silver on the surface of fibers showed an increasing trend from 0.27 to 0.94 at. %, a trend attributed to the dispersion of nano silver in the spinning solution (Figure 5a4–c4).

Figure 5.

Figure 5

Open in a new tab

SEM images, fiber diameter distributions, and EDS of Ag-loaded ST/VPA fibers with nano silver of 15% (w/w) (a1–4), 20% (w/w) (b1–4), and 25% (w/w) (c1–4).

2.5. Structure and Properties of Ag-Loaded Fibers

Figure 6 shows the crystalline structures and thermal properties of Ag-loaded fibers with different nano silver contents. Comparing with the XRD patterns of pure ST/PVA fibers in Figure 3b, a new sharp peak appeared at 2θ of 38° for all of the Ag-loaded fibers (Figure 6a). As has been widely proven, the peak was the Ag planes (111) and confirmed the existance of nano silver in obtained fibers.35 As shown in Figure 6b,c and Table 3, both Tpeak’s for water evaporation and thermal decomposition were improved with the addition of nano silver in ST/PVAfibers, reflecting that the thermal stabilitly was improved in the presence of nano silver in fibers. The weight loss for water evaporation decreased compared with pure ST/PVA fibers and indicated the decrease of water in fibers. However, the weight loss for thermal decomposition increased with the addition of nano silver, which was probably due to the fact that the nano silver in the fibers could catalyze CO2 elimination from polymer chains and accelerate the degradation process.36

Figure 6.

Figure 6

Open in a new tab

XRD spectra (a) and TG and DTG curves of Ag-loaded fibers: (b) 15, (c) 20, and (d) 25% (w/w).

Table 3. Thermal Parameters of Cross-Linked Ag-Loaded Fibers.

nano silver content % (w/w) Tpeak (°C) W % (w/w)
15 93.6 8.84
284.7 78.74
20 105.8 9.09
277.6 78.43
25 91.6 10.26
281.5 77.67
Open in a new tab

The mechanical properties of as-spun, cross-linked, cross-linked (immersed), and Ag-loaded fibrous membranes are shown in Figure 7 and Table 4. As could be observed, the tensile strenth of the as-spun, cross-linked, and cross-linked (immersed) fibrous membranes was 1.56 ± 0.09, 1.72 ± 0.54, and 1.75 ± 0.25 MPa, respectively. However, the strain at breaking of fibrous membranes was 32.51 ± 3.52, 28.96 ± 4.78, and 27.23 ± 1.98, respectively. The water generated during the cross-linking process would make the fibers adhere slightly to each other and would restrict the fibers from sliding somewhat in the stretching process of fibrous membranes. Thus, there was more fiber breakage but not in the form of sliding during the stretching process, which resulted in the increase in tensile strength. The decrease in strain at break for both cross-linked and cross-linked (immersed) water fibrous membranes further suggested the result (Table 4).

Figure 7.

Figure 7

Open in a new tab

Mechanical curves of fibrous membranes.

Table 4. Mechanical Properties of Fibers.

  mechanical properties
fibers tensile strength (MPa) strain at break (%)
as-spun ST/PVA fibers 1.56 ± 0.09 32.51 ± 3.52
cross-linked ST/PVA fibers 1.72 ± 0.54 28.96 ± 4.78
cross-linked ST/PVA fibers (immersed) 1.75 ± 0.25 27.23 ± 1.98
Ag-loaded ST/PVA fibers (15%) 1.51 ± 0.34 27.21 ± 4.87
Ag-loaded ST/PVA fibers (20%) 1.48 ± 0.18 24.53 ± 3.74
Ag-loaded ST/PVA fibers (25%) 1.24 ± 0.21 21.34 ± 3.48
Open in a new tab

When the nano silver was added into fibers, the tensile strength and strain at break began to decrease (Figure 6). These results were induced by the increase in intermolecular distance that resulted from nano silver. As listed in Table 4, the tensile strength and strain at break of fibrous membranes were decreased from 1.51 ± 0.34 to 1.24 ± 0.21 MPa and from 27.21 ± 4.87 to 21.34 ± 3.48%, respectively. These changes reflected that the mechanical properties of fibrous membranes would be further decreased and therefore further increasing nano silver was not conductive to the application of fibers.

2.6. Antibacterial Analysis of Ag-Loaded Fibers

Figure 8 shows the antibacterial properties against E. coli and S. aureus of ST/PVA fibers loaded with different nano silver contents. From Figure 8a, we could observe that the antibacterial performances of fibrous membranes were increased when the nano silver was increased from 15 to 25%. The diameters of the bacteriostatic zone were increased from 1 to 3.5 mm, which suggested relatively high antibacterial properties against E. coli. The antibacterial properties against S. aureus for the obtained fibers were not obvious (Figure 8b). The diameter of the bacteriostatic zone was just about 2 mm for the fibers with nano silver of 25%, and the fibers with nano silver of 15 and 20% showed almost no antibacterial properties. According to the previous papers, the nano silver showed excellent antibacterial properties against both E. coli and S. aureus, while the growth inhibition of bacteria for E. coli was usually largely than that for S. aureus.37

Figure 8.

Figure 8

Open in a new tab

Optical images of Ag-loaded fiber incubated with E. coli (a) and S. aureus (b) bacteria at 37 °C for 24 h. Inhibition zone (no growth of bacteria) near the coated fabric shows its antibacterial property.

3. Conclusions

The water stability of centrifugally spun ST/PVA ultrafine fibers was greatly improved by vapor phase cross-linking. Optimum parameters for the cross-linking temperature and time were obtained on the basis of the water stability combined with mechanical properties. The resultant Ag-loaded fibrous membranes cross-linked at optimum parameters could be used for antibacterial property testing. The results suggested that the fibrous membranes had antibacterial properties against E. coli and S. aureus. In conclusion, we may provide some help in developing biocompatible, biodegradable, and low-cost antibacterial fiber materials.

4. Materials and Method

4.1. Materials

The food-grade native potato starch was self-prepared. The amylopectin ratio and weight-average molecular weight (Mw) were determined to be 73.35 ± 0.76% and 1.173 × 10,7 respectively.14c,21 The PVA powder (average polymerization degree of 1799 and hydrolysis degree of 95%), nano silver (1000 ppm, diameters: 10-15 nm), sodium hydroxide (AR), glutaraldehyde, and formic acid (AR) were purchased from Aladdin (Shanghai, China). Additionally, the nano silver was prepared in the same way as in commercial applications and directly obtained by dispersing the nano silver powder in water. Therefore, the applied nano silver was safe, nontoxic, and environmentally friendly.

4.2. Cross-Linking of ST/VPA Fibers

The ST/PVA fibers with a starch/PVA mass ratio of 60/40 were prepared by using the centrifugal spinning setup designed by our group (Figure 1), and the spinning solution was obtained by blending a starch solution of 12% (w/w) and a PVA solution of 8% (w/w) with a mass ratio of 50/50 according to our previous report.14c In addition, the parameters of nozzle diameters, rotational speed, and perpendicular distance of the spinneret to the collector were kept at 25 gauge (inner diameter: 0.26 mm) and 12 mm long, 1000 rpm, and 80 mm, respectively. The obtained fibers were then cross-linked by using a mixture solution of formic acid/glutaraldehyde, and experiments were operated in the form of vapor phase. The cross-linker parameters were mainly the parameters listed in Table 1. After cross-linking, the fibers were further dried in the oven at 90 °C for 1 h to remove the unreacted cross-linker. A control experiment was operated by thermal treatment of as-spun ST/PVA fibers at 140 °C for 2 h.

4.3. Preparation of Ag-Loaded ST/PVA Fibers

Nano silver was directly added into the composite ST/PVA solution and continuously magnetically stirred until evenly mixed to obtain the spinning solution. The Ag-loaded fibers with different Ag ratios were then prepared by using the same spinning conditions of the ST/PVA fiber preparation, and the cross-linking experiments were operated according to the optimum parameters obtained from former cross-linking experiments.

4.4. Fiber Morphological and Structural Characterization

The morphologies and element analysis of obtained fibers were investigated by scanning electron microscopy (EDS/EBSD, Carl Zeiss, Germany) after coating with Perkin. The samples with 4 mm2 fibrous membranes were prepared and then mounted on the SEM stub to test at 2 kV. The diameter distribution of fibers was analyzed by the ImageJ2x software (ImageJ2X 2.1.4.7, National Institutes of Health, Bethesda, MD) by measuring about 100 fibers.

FTIR spectra of the ST/PVA fibers were characterized by an infrared spectrometer (Nicolet is50, Thermo Electron Corp., New York, USA) in the range of 4000 to 500 cm–1. To reduce spectral noise, 32 scans were collected for the samples under a resolution of 4 cm–1. X-ray diffraction (Thermo ARL Corp., Ecublens, Switzerland) with Cu Kα radiation (k = 1.5406 Å) was used to characterize the crystal structure changes of fibers. The data were continuously collected with a scanning rate of 2°/min and 2θ range from 5 to 45°.

4.5. Fiber Properties

The thermal behaviors before and after cross-linking fibers were determined using a TGA (Mettler Toledo, Zurich, Switzerland) in N2 from 30 to 500 °C at a heating rate of 15°C/min. The tensile strength of fibrous membranes was determined by using a multi-function stretching instrument (KES-GI, Aichi, Japan). The fibrous membranes were cut into a size of 20 mm long and 5 mm wide and then tested at a tensile rate of 0.1 cm/s under 25 °C. The thicknesses of fibrous membranes ranged from 0.15 ± 0.03 to 0.26 ± 0.11 mm. Each specimen was tested five times, and stress was calculated according to eq 1:14c

4.5. 1

where F is the measured force and S is the measured cross-section of samples (width × thickness).

4.6. Antibacterial Property

The antibacterial property of Ag-loaded ST/PVA fibers against both E. coli (ATCC25922) and S. aureus (ATCC29213) was tested according to the bacteriostatic zone test.38 In brief, the fibrous membranes were cut into circles with diameters of 10 mm. All of the samples were sterilized under 121 °C for 20 min and then placed on an agar plate. Then, the agar plates were incubated for 24 h at 37 °C.

Acknowledgments

We acknowledge the financial support by the Natural Science Foundation of Zhejiang Province (grants LQ21E030011 and LY21E030021). The authors would like to thank the anonymous reviewers for their valuable comments.

The authors declare no competing financial interest.

References

  1. a Adhikari U.; An X.; Rijal N.; Hopkins T.; Khanal S.; Chavez T.; Tatu R.; Sankar J.; Little K. J.; Hom D. B.; Bhattarai N.; Pixley S. K. Embedding magnesium metallic particles in polycaprolactone nanofiber mesh improves applicability for biomedical applications. Acta Biomater. 2019, 98, 215–234. 10.1016/j.actbio.2019.04.061. [DOI] [PubMed] [Google Scholar]; b Al-Tayyar N. A.; Youssef A. M.; Al-Hindi R. Antimicrobial food packaging based on sustainable Bio-based materials for reducing foodborne Pathogens: A review. Food Chem. 2020, 310, 125915. 10.1016/j.foodchem.2019.125915. [DOI] [PubMed] [Google Scholar]; c Deng Y.; Lu T.; Cui J.; Keshari Samal S.; Xiong R.; Huang C. Bio-based electrospun nanofiber as building blocks for a novel eco-friendly air filtration membrane: A review. Sep. Purif. Technol. 2021, 277, 119623. 10.1016/j.seppur.2021.119623. [DOI] [Google Scholar]
  2. Soares R. M. D.; Siqueira N. M.; Prabhakaram M. P.; Ramakrishna S. Electrospinning and electrospray of bio-based and natural polymers for biomaterials development. Mater. Sci. Eng. C 2018, 92, 969–982. 10.1016/j.msec.2018.08.004. [DOI] [PubMed] [Google Scholar]
  3. Kai D.; Liow S. S.; Loh X. J. Biodegradable polymers for electrospinning: Towards biomedical applications. Mat. Sci. Eng. C-Mater. 2014, 45, 659–670. [DOI] [PubMed] [Google Scholar]
  4. a Weitz R. T.; Harnau L.; Rauschenbach S.; Burghard M.; Kern K. Polymer nanofibers via nozzle-free centrifugal spinning. Nano Lett. 2008, 8, 1187–1191. 10.1021/nl080124q. [DOI] [PubMed] [Google Scholar]; b Rogalski J. J.; Bastiaansen C. W.; Peijs T. Rotary jet spinning review–a potential high yield future for polymer nanofibers. NANO 2017, 3, 97–121. [Google Scholar]; c Li X.; Lu Y.; Hou T.; Zhou J.; Wang A.; Zhang X.; Yang B. Jet evolution and fiber formation mechanism of amylopectin rich starches in centrifugal spinning system. J. Appl. Polym. Sci. 2021, 138, 50275. 10.1002/app.50275. [DOI] [Google Scholar]
  5. Chen H. S.; Miller C. E. Centrifugal spinning of metallic glass filaments. Mater. Res. Bull. 1976, 11, 49–54. 10.1016/0025-5408(76)90213-0. [DOI] [Google Scholar]
  6. Angwafo A. V.Fibre and shot formation processes in mineral wool manufacture by centrifugal spinning; University of Herfordshire: 1999. [Google Scholar]
  7. Kustas F. M.; Buchholtz B. W. Lubricious-surface-silicon-nitride rings for high-temperature tribological applications. Tribol. T. 1996, 39, 43–50. 10.1080/10402009608983500. [DOI] [Google Scholar]
  8. Chen K.; Ghosal A.; Yarin A. L.; Pourdeyhimi B. Modeling of spunbond formation process of polymer nonwovens. Polymer 2020, 187, 121902. 10.1016/j.polymer.2019.121902. [DOI] [Google Scholar]
  9. Badrossamay M. R.; McIlwee H. A.; Goss J. A.; Parker K. K. Nanofiber assembly by rotary jet-spinning. Nano Lett. 2010, 10, 2257–2261. 10.1021/nl101355x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Rogalski J. J.; Bastiaansen C. W. M.; Peijs T. PA6 nanofibre production: a comparison between rotary jet spinning and electrospinning. Fibers 2018, 6, 37. 10.3390/fib6020037. [DOI] [Google Scholar]
  11. a Huttunen M.; Kellomäki M. A simple and high production rate manufacturing method for submicron polymer fibres. J. Tissue Eng. Regen. Med. 2011, 5, e239–e243. 10.1002/term.421. [DOI] [PubMed] [Google Scholar]; b Lu Y.; Li Y.; Zhang S.; Xu G.; Fu K.; Lee H.; Zhang X. Parameter study and characterization for polyacrylonitrile nanofibers fabricated via centrifugal spinning process. Eur. Polym. J. 2013, 49, 3834–3845. 10.1016/j.eurpolymj.2013.09.017. [DOI] [Google Scholar]
  12. a Xu W.; Xia L.; Zhou X.; Xi P.; Cheng B.; Liang Y. Hollow carbon microfibres fabricated using coaxial centrifugal spinning. Micro Nano Lett. 2016, 11, 74–76. 10.1049/mnl.2015.0346. [DOI] [Google Scholar]; b Jia H.; Dirican M.; Zhu J.; Chen C.; Yan C.; Zhu P.; Li Y.; Guo J.; Caydamli Y.; Zhang X. High-performance SnSb@ rGO@ CMF composites as anode material for sodium-ion batteries through high-speed centrifugal spinning. J. Alloy. Compd. 2018, 752, 296–302. [Google Scholar]
  13. Xu H.; Chen H.; Li X.; Liu C.; Yang B. A comparative study of jet formation in nozzle-and nozzle-less centrifugal spinning systems. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1547–1559. 10.1002/polb.23596. [DOI] [Google Scholar]
  14. a Li X.; Liu J.; Lu Y.; Hou T.; Zhou J.; Zhang X.; Zhou L.; Sun M.; Xue J.; Yang B. Melting centrifugally spun ultrafine poly butylene adipate-co-terephthalate (PBAT) fiber and hydrophilic modification. RSC Adv. 2021, 11, 27019–27026. 10.1039/D1RA04399D. [DOI] [PMC free article] [PubMed] [Google Scholar]; b Chen H.; Li X.; Li N.; Yang B. Electrostatic-assisted centrifugal spinning for continuous collection of submicron fibers. Text. Res. J. 2017, 87, 2349–2357. 10.1177/0040517516671121. [DOI] [Google Scholar]; c Li X.; Liu J.; Lu Y.; Hou T.; Zhou J.; Wang A.; Zhang X.; Yang B. Centrifugally spun starch/polyvinyl alcohol ultrafine fibrous membrane as environmentally-friendly disposable nonwoven. J. Appl. Polym. Sci. 2021, 138, 51169. 10.1002/app.51169. [DOI] [Google Scholar]
  15. Chen H.; Xu H.; Sun J.; Liu C.; Yang B. Effective method for high-throughput manufacturing of ultrafine fibres via needleless centrifugal spinning. Micro Nano Lett. 2015, 10, 81–84. [Google Scholar]
  16. Xiong C.; Li X.; Hou T.; Yang B. Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning. J. Appl. Polym. Sci. 2018, 135, 46072. 10.1002/app.46072. [DOI] [Google Scholar]
  17. Liu C.; Sun J.; Shao M.; Yang B. A comparison of centrifugally-spun and electrospun regenerated silk fibroin nanofiber structures and properties. RSC Adv. 2015, 5, 98553–98558. 10.1039/C5RA15486C. [DOI] [Google Scholar]
  18. Hou T.; Li X.; Lu Y.; Yang B. Highly porous fibers prepared by centrifugal spinning. Mater. Des. 2017, 114, 303–311. 10.1016/j.matdes.2016.11.019. [DOI] [Google Scholar]
  19. Lu Y.; Li X.; Hou T.; Yang B. Centrifugally spun of alginate-riched submicron fibers from alginate/polyethylene oxide blends. Polym. Eng. Sci. 2018, 58, 1644–1651. 10.1002/pen.24754. [DOI] [Google Scholar]
  20. a Wang A.; Li X.; Hou T.; Lu Y.; Zhou J.; Zhang X.; Yang B. A tree-grapes-like PTFE fibrous membrane with super-hydrophobic and durable performance for oil/water separation. Sep. Purif. Technol. 2021, 275, 119165. 10.1016/j.seppur.2021.119165. [DOI] [Google Scholar]; b Wang A.; Li X.; Hou T.; Lu Y.; Zhou J.; Zhang X.; Yang B. High efficiency, low resistance and high temperature resistance PTFE porous fibrous membrane for air filtration. Mater. Lett. 2021, 295, 129831. 10.1016/j.matlet.2021.129831. [DOI] [Google Scholar]
  21. Li X.; Chen H.; Yang B. Centrifugally spun starch-based fibers from amylopectin rich starches. Carbohydr. Polym. 2016, 137, 459–465. 10.1016/j.carbpol.2015.10.079. [DOI] [PubMed] [Google Scholar]
  22. Li X.; Hou T.; Lu Y.; Yang B. A method for controlling the surface morphology of centrifugally spun starch-based fibers. J. Appl. Polym. Sci. 2018, 135, 45810. 10.1002/app.45810. [DOI] [Google Scholar]
  23. a Kong L.; Ziegler G. R. Role of molecular entanglements in starch fiber formation by electrospinning. Biomacromolecules 2012, 13, 2247–2253. 10.1021/bm300396j. [DOI] [PubMed] [Google Scholar]; b Lancuski A.; Vasilyev G.; Putaux J.-L.; Zussman E. Rheological properties and electrospinnability of high-amylose starch in formic acid. Biomacromolecules 2015, 16, 2529–2536. [DOI] [PubMed] [Google Scholar]
  24. Liu G.; Gu Z.; Hong Y.; Cheng L.; Li C. Electrospun starch nanofibers: Recent advances, challenges, and strategies for potential pharmaceutical applications. J. Controlled Release 2017, 252, 95–107. [DOI] [PubMed] [Google Scholar]
  25. a Kong L.; Ziegler G. R. Fabrication of pure starch fibers by electrospinning. Food Hydrocolloid. 2014, 36, 20–25. [Google Scholar]; b Li X.; Hou T.; Lu Y.; Yang B. Citric acid cross-linking of centrifugally spun starch-based fibres. Micro Nano Lett. 2017, 12, 693–696. [Google Scholar]
  26. Wang W.; Jin X.; Zhu Y.; Zhu C.; Yang J.; Wang H.; Lin T. Effect of vapor-phase glutaraldehyde crosslinking on electrospun starch fibers. Carbohyd. Polym. 2016, 140, 356–361. [DOI] [PubMed] [Google Scholar]
  27. Li X.; Lu Y.; Hou T.; Zhou J.; Yang B. Centrifugally spun ultrafine starch/PEO fibres as release formulation for poorly water-soluble drugs. Micro Nano Lett. 2018, 13, 1688–1692. [Google Scholar]
  28. a Tudu B. K.; Sinhamahapatra A.; Kumar A. Surface Modification of Cotton Fabric Using TiO2 Nanoparticles for Self-Cleaning, Oil-Water Separation, Antistain, Anti-Water Absorption, and Antibacterial Properties. ACS Omega 2020, 5, 7850–7860. [DOI] [PMC free article] [PubMed] [Google Scholar]; b Tehrani F. A.; Ahmadiani A.; Niknejad H. The effects of preservation procedures on antibacterial property of amniotic membrane. Cryobiology 2013, 67, 293–298. [DOI] [PubMed] [Google Scholar]
  29. a Qiu C.; Li X.; Ji N.; Qin Y.; Sun Q.; Xiong L. Rheological properties and microstructure characterization of normal and waxy corn starch dry heated with soy protein isolate. Food Hydrocolloid. 2015, 48, 1–7. [Google Scholar]; b Yassaroh Y.; Woortman A. J. J.; Loos K. A new way to improve physicochemical properties of potato starch. Carbohyd. Polym. 2019, 204, 1–8. [DOI] [PubMed] [Google Scholar]
  30. Kizil R.; Irudayaraj J.; Seetharaman K. Characterization of irradiated starches by using FT-Raman and FTIR spectroscopy. J. Agr. Food. Chem. 2002, 50, 3912–3918. [DOI] [PubMed] [Google Scholar]
  31. Destaye A. G.; Lin C. K.; Lee C. K. Glutaraldehyde vapor cross-linked nanofibrous PVA mat with in situ formed silver nanoparticles. Acs Appl. Mater. Inter. 2013, 5, 4745–4752. [DOI] [PubMed] [Google Scholar]
  32. Xue B.; Ji L.; Deng J.; Zhang J.. In situ FTIR spectroscopy study on the rapid dissolution process of modified poly(vinyl alcohol). J. Polym. Res. 2016, 23 (). [Google Scholar]
  33. Wang S.; Li C.; Copeland L.; Niu Q.; Wang S. Starch Retrogradation: A Comprehensive Review. Compr. Rev. Food Sci. F. 2015, 14, 568–585. [Google Scholar]
  34. a Peng Z.; Kong L. X. A thermal degradation mechanism of polyvinyl alcohol/silica nanocomposites. Polym. Degrad. Stabil. 2007, 92, 1061–1071. [Google Scholar]; b Zheng T.; Clemons C. M.; Pilla S. Grafting PEG on cellulose nanocrystals via polydopamine chemistry and the effects of PEG graft length on the mechanical performance of composite film. Carbohyd. Polym. 2021, 271, 118405. [DOI] [PubMed] [Google Scholar]
  35. a Larrude D. G.; Maia da Costa M. E. H.; Freire F. L. Synthesis and Characterization of Silver Nanoparticle-Multiwalled Carbon Nanotube Composites. J. Nanomater. 2014, 2014, 1–7. [Google Scholar]; b Park J. K.; Pham-Nguyen O. V.; Yoo H. S. Coaxial Electrospun Nanofibers with Different Shell Contents to Control Cell Adhesion and Viability. ACS Omega 2020, 5, 28178–28185. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. a Chaturvedi A.; Bajpai A. K.; Bajpai J. Preparation and characterization of poly(vinyl alcohol) cryogel-silver nanocomposites and evaluation of blood compatibility, cytotoxicity, and antimicrobial behaviors. Polym. Composite. 2015, 36, 1983–1997. [Google Scholar]; b Bardajee G. R.; Hooshyar Z.; Rezanezhad H. A novel and green biomaterial based silver nanocomposite hydrogel: synthesis, characterization and antibacterial effect. J. Inorg. Biochem. 2012, 117, 367–373. [DOI] [PubMed] [Google Scholar]
  37. a Wang S.; Bai J.; Li C.; Zhang J. Functionalization of electrospun β-cyclodextrin/polyacrylonitrile (PAN) with silver nanoparticles: Broad-spectrum antibacterial property. Appl. Surf. Sci. 2012, 261, 499–503. [Google Scholar]; b Kegere J.; Ouf A.; Siam R.; Mamdouh W. Fabrication of Poly(vinyl alcohol)/Chitosan/Bidens pilosa Composite Electrospun Nanofibers with Enhanced Antibacterial Activities. ACS Omega 2019, 4, 8778–8785. [DOI] [PMC free article] [PubMed] [Google Scholar]; c Xiao Y.; Wang Y.; Zhu W.; Yao J.; Sun C.; Militky J.; Venkataraman M.; Zhu G. Development of tree-like nanofibrous air filter with durable antibacterial property. Sep. Purif. Technol. 2021, 259, 118135. [Google Scholar]

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES