Lysine-Grafted MCM-41 Silica as an Antibacterial Biomaterial

Abstract

This paper proposes a facile strategy for the zwitterionization of bioceramics that is based on the direct incorporation of l-lysine amino acid via the ε-amino group onto mesoporous MCM-41 materials. Fourier transform infrared (FTIR) studies of lysine-grafted MCM-41 (MCM-LYS) simultaneously showed bands at 3080 and 1540 cm−1 and bands at 1625 and 1415 cm−1 corresponding to -NH3+/COO− pairs, which demonstrate the incorporation of the amino acid on the material surface keeping its zwitterionic character. Both elemental and thermogravimetric analyses showed that the amount of grafted lysine was 8 wt. % based on the bioceramic total weight. Moreover, MCM-LYS exhibited a reduction of adhesion of S. aureus and E. coli bacteria in 33% and 50%, respectively at physiological pH, as compared with pristine MCM-41. Biofilm studies onto surfaces showed that lysine functionalization elicited a reduction of the area covered by S. aureus biofilm from 42% to only 5% (88%). This research shows a simple and effective approach to chemically modify bioceramics using single amino acids that provides zwitterionic functionality, which is useful to develop new biomaterials that are able to resist bacterial adhesion.

Nanomaterials as Promising Alternative in the Infection Treatment

“…Another strategy would be the direct functionalization with low-molecular weight moieties bearing the same number of negative and positive charges. In this case, some amino acids can be used due their biocompatibility but they cannot be rigorously considered as zwitterions due to the presence of ionizable groups, providing a nonpermanent or pH dependent zwitterion-like action at the isoelectric point [46,47]. However, this could be taken as an advantage since the infectious process (the environment) is enclosed in certain conditions of acidity compared to normal physiological conditions.…”

The Role of Zwitterionic Materials in the Fight against Proteins and Bacteria

“…Furthermore, it is possible to confer biomaterials of zwitterionic nature by decorating their surface with low-molecular weight moieties bearing the same number of negative and positive charges (Figure 3). For instance, it is possible to functionalize with different amino acids, such as cysteine and lysine [43,44,45], sulfobetaine derivatives [46,47,48], or dopamine [49,50,51], exhibiting zwitterionic characteristics depending on the pH. Although the reported methods usually require several synthetic steps involving different intermediate products, they offer distinct advantages when compared to zwitterionic polymers, since they are usually associated to relatively more simple methods and lead to more biocompatible surfaces.…”

“…The synergistic combination of zwitterionic nature and antibiotic hosting capability opens up a new insight in the management of bone-associated infections. Zwitterionization has been also implemented on mesoporous bioactive glasses (MBG) having the SiO 2 –CaO–P 2 O 5 composition [44]. These MBG are a type are nanostructured bioceramics analogous in composition to conventional bioglasses but exhibiting outstanding bioactive and cell response behaviors [69,72].…”

Mesoporous Silica Nanoparticles for the Treatment of Complex Bone Diseases: Bone Cancer, Bone Infection and Osteoporosis

“…In addition, there are some amino acids that are useful for the design of this kind of surfaces. For instance, the amino acid lysine presents this behavior owing to the -NH 3 + /COO − pairs and has been grafted to MSNs [181] and silica-based mesoporous bioactive glasses [182], leading to reduced bacterial adhesion and biofilm formation. A similar approach consists in using the amino acid cysteine to obtain neutral surfaces, yielding MSNs with high stability in human serum [183].…”