Colloidal Surface Engineering: Growth of Layered Double Hydroxides with Intrinsic Oxidase‐Mimicking Activities to Fight Against Bacterial Infection in Wound Healing

Abstract

Colloidal surface engineering is of particular importance to impart modular functionalities to the colloidal systems. Here, a layer of Mn/Ni layered hydroxides (Mn/Ni(OH)x LDHs) can be successfully coated on various colloidal particles, such as silica spheres, silica rods, ferrite nanocrystal supraparticles, as well as FeOOH nanorods. Such layered hydroxides have intrinsic oxidase‐mimetic activities, as demonstrated by catalytic oxidation of tetramethyl benzidine in the presence of oxygen. Furthermore, Mn/Ni(OH)x LDHs structure seems to capture bacteria (both Gram positive and Gram negative) and exhibit antibacterial properties in vitro. Moreover, local delivery of Mn/Ni‐LDH structure fights against infection and reverses delayed wound healing procedures in mice models. Importantly, such hierarchical structures may have strong adhesive properties to the bacteria, which may maximize the contact between Mn/Ni(OH)x LDHs and the bacteria's surface. Overall, the present versatile colloidal surface engineering strategy will bring new insights in the field of antibiotics for its high efficiency toward antibacterial activity.

Direct contact, dissolution and generation of reactive oxygen species: How to optimize the antibacterial effects of layered double hydroxides

“…Such findings come in line with those of Wang et al who reported the enhancement of lysosomal antibacterial function by loading lysozyme at the surface of ternary MgZnAl LDHs due to the rough surface of the host LDH providing better contact with bacteria and thus an amplified antibacterial effect [71]. Although these investigations suggest that the rough surface of LDHs aid in the adhesion phenomena leading to the achieved antibacterial effect [50,71], real measurements of LDH surface roughness are lacking. One good method to ensure the effectiveness of LDHs roughness in the antibacterial activity is to compare the antibacterial activity of different LDH samples having different surface roughness which could be evaluated easily by atomic force microscopy (AFM) for example [75,76].…”

“…One other possible reason explaining LDH-bacteria adhesion is the rough surface of LDHs thus promoting the adhesion phenomena which may be a key factor contributing to their antibacterial activity [50,71]. In fact, it had been well known that the motility of bacteria is essential for bacterial normal functions [72], and that rough antimicrobial colloidal surfaces might adhere to bacteria and disturb its normal motility functions [73].…”

“…The previously mentioned investigations succeeded to correlate direct surface interactions between bacteria and LDHs to their antibacterial activity. However, the used experimental approaches were only achieved through the evaluation of the effect of LDH particle sizes [9,82] or else through qualitative adhesion observations using SEM or TEM imaging [50,71] without any quantification of the driving forces of interactions. In fact, there are other methods which can be used to investigate and quantify LDHs-bacterial membrane.…”

“…In fact, it had been well known that the motility of bacteria is essential for bacterial normal functions [72], and that rough antimicrobial colloidal surfaces might adhere to bacteria and disturb its normal motility functions [73]. Zhang et al had successfully synthesized antibacterial hybrids of (SiO2) nanorods @ Mn/Ni LDHs by coating silica (SiO2) nanorods with unsmooth hollow Mn/Ni LDH NPs [50]. The antibacterial activities of SiO2, Mn/Ni LDHs and SiO2 nanorods @Mn/Ni LDHs were investigated against Gram-negative E. coli and Gram-positive Staphylococcus aureus bacteria, by a standard cell viability Live/Dead Bac Light assay (Figure . 4A).…”

“…2 illustrates the three different suggested mechanisms explaining the antimicrobial activity of these different types of antibacterial LDHs. The first is the direct surface interactions between pristine and NPs-loaded LDHs with the bacteria thus leading to their growth inhibition or death [41,44,46,48,50]. The second comprise the dissolution antibacterial molecules present in the LDH interlaminar region of antibacterial molecules-loaded LDH composites [45,51].…”