Ahmed Al-Mamoori

ahmed al-mamoori

PhD student

Ahmed Al-Mamoori started his PhD project in the Paunov Research Group at the Department of Chemistry of the University of Hull in October 2015.

PhD supervisors: Prof. Vesselin N. Paunov (PI) and Dr Tommy Horozov (Co-PI)

Research project 1:

Self-grafting copper oxide nanoparticles with ultra-enhanced antibacterial action

Copper oxide nanoparticles (CuONPs) have been widely recognized as good antimicrobial agents but are heavily regulated due to environmental concerns of their post use. In this work, we have developed and tested a novel type of formulation for copper oxide (CuONPs) which have been functionaliazed with (3-Glycidyloxypropyl)trimethoxysilane (GLYMO) to allow further covalent coupling of 4-hydroxyphenylboronic acid (4-HPBA).

self-grafting CuONPs-Fig1

Figure 1. Schematics for preparation of self-grafting CuONPs.

As the boronic acid (BA) groups on the surface of CuONPs/GLYMO/4-HPBA can form reversible covalent bonds with the diol groups of glycoproteins on the bacterial cell surface, they can strongly bind to the cells walls resulting in a very strong enhancement of their antibacterial action which is not based on electrostatic adhesion [1].

Self-Grafting CuONPs-Fig1

Figure 2. The interaction between the CuONPs with boronic acid surface functionality and the sugar groups on the surface of the bacterial cell wall leads to their attachment to the bacterial cell wall which strongly amplifies their antibacterial action. TEM images of E.coli after exposure to CuONPs/GLYMO/HPBA.

 SEM and TEM imaging revealed that 4-HPBA-functionalized nanoparticles could accumulate more on the cell surface than non-functionalized ones (see Fig. 2). We demonstrate that the CuONPs with boronic acid surface functionality are far superior antibacterial agents compared to bare CuONPs. Our results showed that, the antibacterial impact of the 4-HPBA functionalized CuONPs on E.coli and R. rhodochrous is one order of magnitude higher than that of bare CuONPs or CuONPs/GLYMO (see Fig. 3).

Self-Grafting CuONPs-Fig3

Figure 3. Comparison of the cell viobility of R. rhodochrous after exposure to bare CuONPs, CuONPs/GLYMO and CuONPs/GLYMO/HPBA.

We also observed a marked increase of the 4-HPBA functionalized CuONPs antibacterial action on these microorganisms at shorter incubation times compared with the bare CuONPs at the same conditions. We show that the cytotoxicity of CuONPs functionalized with 4-HPBA as an outer layer can be controlled by the concentration of glucose in the media and that the effect is reversible as glucose competes with the sugar residues on the bacterial cell walls for the BA-groups on the CuONPs. Our experiments with human keratinocytes exposure to CuONPs/GLYMO/4-HPBA indicated lack of measurable cytotoxicity at particle concentration which are effective as antibacterial agent for both bacteria. We envisage that formulations of CuONPs/GLYMO/4-HPBA can be used to drastically reduce the overall CuO concentration in antimicrobial formulations while strongly increasing their efficiency. We recently demonstrated that the same strategy works for anti-algal and anti-yeast formulations. [2]

References

1. Halbus, A.F., Horozov, T.S., Paunov, V.N., Strongly enhanced antibacterial action of copper oxide nanoparticles with boronic acid surface functionalityACS Appl. Mater. Inter.,  11 (2019) 12232–12243.

2. Halbus, A.F., Horozov, T.S., Paunov, V.N., Self-grafting copper oxide nanoparticles show a strong enhancement of their anti-algal and anti-yeast actionNanoscale Advances,   1 (2019) 2323 – 2336.