Charge‐directed targeting of antimicrobial protein‐nanoparticle conjugates

Abstract

Use of antimicrobial enzymes covalently attached to nanoparticles is of great interest as an antibiotic-free approach to treat microbial infections. Intrinsic properties of nanoparticles can also be used to add functionality to their conjugates with biomolecules. Here, we show in a model system that nanoparticle charge can be used to enhance delivery and increase bactericidal activity of an antimicrobial enzyme, lysozyme. Hen egg lysozyme was covalently attached to two types of polystyrene latex nanoparticles: positively charged, containing aliphatic amine surface groups, and negatively charged, containing sulfate and chloromethyl surface groups. In the case of bacterial lysis assay with a Gram-positive bacteria Micrococcus lysodeikticus, activity of lysozyme conjugated to positively charged nanoparticles was approximately twice as large as that of free lysozyme, while lysozyme conjugated to negatively charged nanoparticles showed little detectable activity. At the same time, when assayed using a low-molecular weight oligosaccharide substrate, lysozyme attached to both positively and negatively charged nanoparticles showed slightly lower activity than free enzyme. A possible explanation of these results is that lysozyme attached to negatively charged nanoparticles cannot be effectively targeted to the bacteria because of the electrostatic Coulombic repulsion from the negatively charged bacterial cell walls, whereas lysozyme conjugated to positively charged nanoparticles was targeted better than free enzyme due to stronger electrostatic attraction to bacteria. Zeta potential measurements confirmed the validity of this hypothesis. Thus, nanoparticle charge is an important factor that can be used to control targeting and activity of protein-nanoparticle conjugates.

Surface Modification of Polymer Substrates for Biomedical Applications

“…Similar result was achieved when utilizing BPD to anchor nanoparticles to the surface of PE [111]. The plasma pre-treatment, as well as the final grafting of the noble metal nanoparticles also leads to a significant change in zeta potential, due to the change in the surface charge of the polymer cause by the increase in polar groups in the surface layer [114]. Pt and Pd nanoparticles caused a significant shift towards a positive charge [107], while Au nanoparticles (Figure 7), on the other hand, cause a dramatic decrease well below the values of the pristine polymer substrate, greatly increasing the conductivity of the grafted surface, which is also known to improve biocompatibility [111].…”

Synthesis and characterization of monodispersed P(St-co-DMAEMA) nanoparticles as pH-sensitive drug delivery system

“…However, when the NPs extravasate from the vasculature, the positive charge will induce electrostatic interaction between NPs and tumor cells which have a negative charge on their membrane. The electrostatic interaction might enhance the retention of NPs within the tumor and cellular uptake of NPs [37,38].…”

Antibiotic‐Free Antibacterial Strategies Enabled by Nanomaterials: Progress and Perspectives

“…Copyright 2016, Elsevier. (c) Reproduced with permission . Copyright 2008, Wiley Periodicals, Inc. (d) Reproduced with permission 115b.…”

“…Recent studies have revealed that the structural properties of nanomaterials play an important role in enhancing the interaction with the bacterial membrane and the bactericidal activity of lysozyme . The activity of lysozyme after immobilization in positively charged particles (Figure c) was twice as large as that of free lysozyme, while very limited activity was detected in the bacterial lysis study when lysozyme was conjugated on negatively charged particles . Recently, we demonstrated that small‐sized (79 nm) mesoporous silica nanoparticles (MSNs) with a large pore size (22.4 nm) enhanced lysozyme delivery by effective membrane attachment and subsequent membrane disintegration.…”