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.
Highlights
In the recent past, foodborne illnesses and nosocomial infections occurred during hospitalization have been identified as two major problems that have been producing many economic and human losses
polyvinyl alcohol (PV) and polyvinyl alcohol nanofibers (PVN) clearly prese1n1toefd17 the main absorption bands of this polymer, PVN nanofibers did not show the presence of the peak aasssosocciaiateteddtotoththeecrcyrystsatal lsesqequueenncceererlealateteddtotoCC–O–Ostsrtertecthchininggatat11141343cmcm−1−1dduueetotoththeererdeduuctcitoionnoof f crcyrystsatalllilninitiytyoof fththeeppoolylymmeerrcacauuseseddbbyyththeeeelelecctrtorospspininnnininggpprorocecesss,s,aassititwwaassaalrlereaaddyysseeeennththrorouugghhDDRRXX aannaalylysissis[4[44,45,353,5,544].].TThhisisfafcatctwwasasalasolsoeveivdiednecnecdedbybay raedruedctuioctnioonf roaftiroat(iDo 1(1D451/14D5/D10190696))wwhhicichhhhaaddbbeeeenn clcoloseselylyrerelalateteddtotoddeeggrreeeeooffccrryyssttaalllliinniittyy [[5555]]
When exposed to UVA light, TDN presented interesting antimicrobial capacities and, as it was expected, the reduction in all bacterial concentrations increased as the concentration of titanium dioxide nanotubes increased
Summary
Foodborne illnesses and nosocomial infections occurred during hospitalization have been identified as two major problems that have been producing many economic and human losses. In this work, electrospinning (EP) and atomic layer deposition (ALD) technologies were combined with the objective to develop novel antimicrobial nanotubes with well-defined nanoscale walls composed of titanium dioxide. ALD has been recognized as a key technology for the surface modification and the fabrication of nanostructures materials because it is the only applicable technique for the deposition of conformal and homogenous thin films [18]. This technique allows to deposit thin films in structures with complex geometries allowing to synthesize high aspect ratio nanostructures without shadowing effects [19]. Jian et al have developed TiO2 and silver loaded-TiO2 antibacterial agents through sol-assay method with minimum inhibition concentration values around 1.6 mg/mL [31,32]
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