Nanoparticles of Quaternary Ammonium Polyethylenimine Derivatives for Application in Dental Materials

Abstract

Various quaternary ammonium polyethylenimine (QA-PEI) derivatives have been synthesized in order to obtain nanoparticles. Due to their antibacterial activity and non-toxicity towards mammalian cells, the QA-PEI nanoparticles have been tested extensively regarding potential applications as biocidal additives in various dental composite materials. Their impact has been examined mostly for dimethacrylate-based restorative materials; however, dental cements, root canal pastes, and orthodontic adhesives have also been tested. Results of those studies showed that the addition of small quantities of QA-PEI nanoparticles, from 0.5 to 2 wt.%, led to efficient and long-lasting antibacterial effects. However, it was also discovered that the intensity of the biocidal activity strongly depended on several chemical factors, including the degree of crosslinking, length of alkyl telomeric chains, degree of N-alkylation, degree of N-methylation, counterion type, and pH. Importantly, the presence of QA-PEI nanoparticles in the studied dental composites did not negatively impact the degree of conversion in the composite matrix, nor its mechanical properties. In this review, we summarized these features and functions in order to present QA-PEI nanoparticles as modern and promising additives for dental materials that can impart unique antibacterial characteristics without deteriorating the products' structures or mechanical properties.

Keywords: antibacterial agents; dental composite restorative materials; nanoparticles; quaternary ammonium polyethylenimine.

Figure 1

The synthesis of (a) linear polyethylenimine, (b) branched polyethylenimine. Adapted from [31].

Figure 2

Formation of crosslinked polyethylenimine (PEI) nanoparticles. Adapted from [60].

Figure 3

Telomerization in the N-alkylation method with the use of 1-bromooctane. Adapted from [60].

Figure 4

Telomerization in the reductive amination method with the use of octanal. Adapted from [60].

Figure 5

The quaternization step that occurs in both methods. Adapted from [60].

Figure 6

Antibacterial activity of QA-PEI nanoparticles alkylated with different N-alkylation agents and with various degrees of N-alkylation. Data from [84].

Figure 7

S. mutans growth (%) on the surface of a commercial dental composite enriched with 1 wt.% QA-PEI nanoparticles, which were telomerized using alkyl bromides of various lengths. Data from [85].

Figure 8

The minimum inhibitory concentration (MIC) (µg/mL) values of fully quaternized linear QA-PEIs obtained using various bromides and tested against S. mutans and P. aeruginosa. Data from [86].

Figure 9

Concentration of QA-PEI nanoparticles (mg/mL) with varying degrees of telomerization required for complete inhibition of S. aureus growth. Data from [60].

Figure 10

S. mutans growth (%) on the surface of a restorative composite resin containing 1 wt.% quaternized and non-quaternized QA-PEI nanoparticles. Data from [85].

Figure 11

MIC (µg/mL) values measured for linear QA-PEI, distinguished by their quaternization degree and N-alkyl substituents, in tests against S. aureus and P. aeruginosa. Data from [86].

Figure 12

Degree of conversion of orthodontic adhesives modified with QA-PEI nanoparticles. Data from [94].