Time of flight secondary ion mass spectrometry-A method to evaluate plasma-modified three-dimensional scaffold chemistry

Low-Temperature Plasma Techniques in Biomedical Applications and Therapeutics: An Overview

Plasma, the fourth fundamental state of matter, comprises charged species and electrons, and it is a fascinating medium that is spread over the entire visible universe. In addition to that, plasma can be generated artificially under appropriate laboratory techniques. Artificially generated thermal or hot plasma has applications in heavy and electronic industries; however, the non-thermal (cold atmospheric or low temperature) plasma finds its applications mainly in biomedicals and therapeutics. One of the important characteristics of LTP is that the constituent particles in the plasma stream can often maintain an overall temperature of nearly room temperature, even though the thermal parameters of the free electrons go up to 1 to 10 keV. The presence of reactive chemical species at ambient temperature and atmospheric pressure makes LTP a bio-tolerant tool in biomedical applications with many advantages over conventional techniques. This review presents some of the important biomedical applications of cold-atmospheric plasma (CAP) or low-temperature plasma (LTP) in modern medicine, showcasing its effect in antimicrobial therapy, cancer treatment, drug/gene delivery, tissue engineering, implant modifications, interaction with biomolecules, etc., and overviews some present challenges in the field of plasma medicine.

Back to the basics of time-of-flight secondary ion mass spectrometry of bio-related samples. I. Instrumentation and data collection

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used widely throughout industrial and academic research due to the high information content of the chemically specific data it produces. Modern ToF-SIMS instruments can generate high mass resolution data that can be displayed as spectra and images (2D and 3D). This enables determining the distribution of molecules across and into a surface and provides access to information not obtainable from other methods. With this detailed chemical information comes a steep learning curve in how to properly acquire and interpret the data. This Tutorial is aimed at helping ToF-SIMS users to plan for and collect ToF-SIMS data. The second Tutorial in this series will cover how to process, display, and interpret ToF-SIMS data.

Melimine-Modified 3D-Printed Polycaprolactone Scaffolds for the Prevention of Biofilm-Related Biomaterial Infections

Biomaterial-associated infections are one of the major causes of implant failure. These infections result from persistent bacteria that have adhered to the biomaterial surface before, during, or after surgery and have formed a biofilm on the implant's surface. It is estimated that 4 to 10% of implant surfaces are contaminated with bacteria; however, the infection rate can be as high as 30% in intensive care units in developed countries and as high as 45% in developing countries. To date, there is no clinical solution to prevent implant infection without relying on the use of high doses of antibiotics supplied systemically and/or removal of the infected device. In this study, melimine, a chimeric cationic peptide that has been tested in Phase I and II human clinical trials, was immobilized onto the surface of 3D-printed medical-grade polycaprolactone (mPCL) scaffolds via covalent binding and adsorption. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of melimine-treated surfaces confirmed immobilization of the peptide, as well as its homogeneous distribution throughout the scaffold surface. Amino acid analysis showed that melimine covalent and noncovalent immobilization resulted in a peptide density of ∼156 and ∼533 ng/cm², respectively. Furthermore, we demonstrated that the immobilization of melimine on mPCL scaffolds by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) coupling and noncovalent interactions resulted in a reduction of Staphylococcus aureus colonization by 78.7% and 76.0%, respectively, in comparison with the nonmodified control specimens. Particularly, the modified surfaces maintained their antibacterial properties for 3 days, which resulted in the inhibition of biofilm formation in vitro. This system offers a biomaterial strategy to effectively prevent biofilm-related infections on implant surfaces without relying on the use of prophylactic antibiotic treatment.

Mass spectrometry as a tool to advance polymer science

In contrast to natural polymers, which have existed for billions of years, the first well-understood synthetic polymers date back to just over one century ago. Nevertheless, this relatively short period has seen vast progress in synthetic polymer chemistry, which can now afford diverse macromolecules with varying structural complexities. To keep pace with this synthetic progress, there have been commensurate developments in analytical chemistry, where mass spectrometry has emerged as the pre-eminent technique for polymer analysis. This Perspective describes present challenges associated with the mass-spectrometric analysis of synthetic polymers, in particular the desorption, ionization and structural interrogation of high-molar-mass macromolecules, as well as strategies to lower spectral complexity. We critically evaluate recent advances in technology in the context of these challenges and suggest how to push the field beyond its current limitations. In this context, the increasingly important role of high-resolution mass spectrometry is emphasized because of its unrivalled ability to describe unique species within polymer ensembles, rather than to report the average properties of the ensemble.

Time-of-flight secondary ion mass spectrometry three-dimensional imaging of surface modifications in poly(caprolactone) scaffold pores

Scaffolds composed of synthetic polymers such as poly(caprolactone) (PCL) are widely used for the support and repair of tissues in biomedicine. Pores are common features in scaffolds as they facilitate cell penetration. Various surface modifications can be performed to promote key biological responses to these scaffolds. However, verifying the chemistry of these materials post surface modification is problematic due to the combination of three-dimensional (3D) topography and surface sensitivity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is commonly used to correlate surface chemistry with cell response. In this study, 3D imaging mass spectrometry analysis of surface modified synthetic polymer scaffolds is demonstrated using PCL porous scaffold, a pore filling polymer sample preparation, and 3D imaging ToF-SIMS. We apply a simple sample preparation procedure, filling the scaffold pores with a poly(vinyl alcohol)/glycerol mixture to remove topographic influence on image quality. This filling method allows the scaffold (PCL) and filler secondary ions to be reconstructed into a 3D chemical image of the pore. Furthermore, we show that surface modifications in the pores of synthetic polymer scaffolds can be mapped in 3D. Imaging of "dry" and "wet" surface modifications is demonstrated as well as a comparison of surface modifications with relatively strong ToF-SIMS peaks (fluorocarbon films [FC]) and to more biologically relevant surface modification of a protein (bovine serum albumin [BSA]). We demonstrate that surface modifications can be imaged in 3D showing that characteristic secondary ions associated with FC and BSA are associated with C3 F8 plasma treatment and BSA, respectively within the pore.