Novel Antimicrobial Titanium Dioxide Nanotubes Obtained through a Combination of Atomic Layer Deposition and Electrospinning Technologies

Abstract

The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 μg/mL concentration.

Antimicrobial Bilayer Nanocomposites Based on the Incorporation of As-Synthetized Hollow Zinc Oxide Nanotubes

“…Although the electrospinning process reduces polymer crystallinity, electrospun PVf demonstrated a semi-crystalline nature through the presence of a sharp peak at 2Ɵ = 22.5°, which is characteristic of a monoclinic PV crystal structure [35]. The deposition of this metal oxide over PV nanofibers (sample ZnO-PVf) enhanced this polymer crystallinity, and a new characteristic PV crystalline peak was evidenced at 19.5° [31,35,36]. Probably, the electrospun PV fibers exposition to the ALD chamber temperature (150 °C) and further cooling allowed the reorganization of PV polymeric chains.…”

“…Electrospun poly(vinyl alcohol) nanofibers (PV f ) were developed by using an electrospinning system (Spraybase ® power Supply Unit, Maynooth, Ireland), according to our previous work [31]. Poly(vinyl alcohol) solution at 8% (w/v) was prepared in distilled water with stirring at 90 • C. The polymeric solution was transferred in a 5 mL plastic syringe and connected through a polytetrafluoroethylene tube to a stainless steel needle of 1.6 mm diameter charged by a high-voltage power supply with a range of 0-20 kV.…”

“…The increase in calcination temperature produced an increase in the size of the ZnO grains from 45 nm for 450 • C to approximately 200 nm for 600 • C. This abrupt change in grain size was primarily responsible for the collapse of tubular morphology. On the other hand, the application of a higher calcination temperature produced a more aggressive thermal decomposition of the polymer, causing fractures of the nanotubes due to the release of compounds (water and acetaldehyde by-products) [31].…”

“…This abrupt change in grain size was primarily responsible for the collapse of tubular morphology. On the other hand, the application of a higher calcination temperature produced a more aggressive thermal decomposition of the polymer, causing fractures of the nanotubes due to the release of compounds (water and acetaldehyde by-products) [31]. Therefore, both the increase in grain size and the thermal decomposition of the polymer contributed to the shape of the nanotubes collapse at 600 • C. On the other hand, when the calcination occurred at 450 • C, the tubular morphology was maintained (Figure 1c,d).…”

Improving polyphenolic thermal stability ofAristotelia Chilensisfruit extract by encapsulation within electrospun cyclodextrin capsules

“…In addition, unlike other encapsulation techniques, such as spray drying, these technologies do not require high‐temperature conditions, being greatly effective for the encapsulation of thermos‐sensitive substances. In both techniques, an electrical potential is applied between a droplet of a matrix solution held at the end of a capillary tube and grounded target and when the applied electric field overcomes the surface tension of the droplet, a charged jet of solution is ejected (López de Dicastillo et al, ). Several works have already shown the effectiveness of encapsulation of active compounds, such as vanillin, curcumin, natural extracts, and essential oils, into different electrospun matrixes such as polymers and proteins (Arrieta, López de Dicastillo, Garrido, Roa, & Galotto., ; Kayaci & Uyar, ; Pérez‐Masiá et al, ; Rieger & Schiffman, ; Salevic, Prieto, Cabedo, Nedovic, & Lagaron, ; Torkamani, Syahariza, Norziah, Wan, & Juliano, ; Wang et al, ).…”