Impact of Surface Functionalization by Nanostructured Silver Thin Films on Thermoplastic Central Venous Catheters: Mechanical, Microscopical and Thermal Analyses

Gregorio Marchiori,Matteo Berni,Devis Bellucci,Valeria Cannillo,Giorgio Cassiolas,Alessandro Gambardella

doi:10.3390/coatings10111034

Abstract

In this work, an interdisciplinary approach was employed to investigate the impact on thermoplastic catheters from the deposition of a thin (180 nm), metallic silver film by a pulsed ablation technique. Our characterization firstly involved tensile and bending tests, each one accompanied by finite element modeling aiming to elucidate the contributions resulting from bulk and coating to the device’s mechanical behavior. The morphological assessment of the surface before and after the deposition was performed by atomic force microscopy, specifically implemented to visualize the nanostructured character of the film surface and the extent to which the polymer was modified by the deposition process, focusing on coating delamination due to tensile stress. Finally, thermogravimetric–differential thermal analysis was carried out to evaluate whether silver deposition has affected the physiochemical structure of the polymer matrix. Our results establish that the deposition does not significantly alter the physical and chemical properties of the device. The presented characterization sets a useful precedent for elucidating how structural properties of polymeric materials may change after coating by electronic ablation techniques, highlighting the importance of employing a comprehensive approach for clarifying the effects of additive manufacturing on medical devices.

Highlights

In the field of biomedical devices, increasing attention is being paid to the usage of nano-fabrication techniques in obtaining specific functionalities related to the biological environment [1,2]
In the paragraphs we focus on the numerical aspects of the mechanical tests and simulations, aiming to separate contributions of Carbothane and Ag on the device mechanical behavior; morphological aspects of the device, considered before and after the deposition, will be be examined examined in in the the paragraph paragraph dedicated dedicated to to Atomic force microscopy (AFM)
It is reasonable to suggest that the inhomogeneous aspect of the coated surface revealed by atomic force microscopy, originated in turn by the strong inheritance of the substrate morphology, could be the reason at the basis of the observed lowering of the coating’s Young’s modulus with respect to bulk

Summary

Introduction

In the field of biomedical devices, increasing attention is being paid to the usage of nano-fabrication techniques in obtaining specific functionalities related to the biological environment [1,2]. The antimicrobial activity of silver has been previously exploited in biomedical devices such as medical and orthopedic implants [7,10,11]; in recent years, specific studies have been carried out on catheters [8,9] with the aim, at the same time, of avoiding infections and keeping under control silver cytotoxicity when in contact with the biological fluids [9] In this perspective, particular attention has been devoted to the fabrication of nanostructures—as size reduction allows us to take advantage of novel physical and chemical properties specific to the nanoscale— to improve the antibacterial efficacy, and not less importantly, to elucidate the physiochemical mechanism at the base of the antimicrobial action [6,12,13,14]. The high non-equilibrium deposition conditions of PEA guarantee preservation of the target stoichiometry and good control upon the physical structure of the films so obtained, making this technique able to meet specific research or application requirements

Methods

Results

Conclusion