Inhibited biofilm formation and improved antibacterial activity of a novel nanoemulsion against cariogenic Streptococcus mutans in vitro and in vivo

Abstract

The aim of this study was to prepare a novel nanoemulsion loaded with poorly water-soluble chlorhexidine acetate (CNE) to improve its solubility, and specifically enhance the antimicrobial activity against Streptococcus mutans in vitro and in vivo . In this study, a novel CNE nanoemulsion with an average size of 63.13 nm and zeta potential of −67.13 mV comprising 0.5% CNE, 19.2% Tween 80, 4.8% propylene glycol, and 6% isopropyl myristate was prepared by the phase inversion method. Important characteristics such as the content, size, zeta potential, and pH value of CNE did not change markedly, stored at room temperature for 1 year. Also, compared with chlorhexidine acetate water solution (CHX), the release profile results show that the CNE has visibly delayed releasing effect in both phosphate-buffered saline and artificial saliva solutions ( P <0.005). The minimum inhibitory concentration and minimum bactericidal concentration of CHX for S. mutans (both 0.8 μg/mL) are both two times those of CNE (0.4 μg/mL). Besides, CNE of 0.8 μg/mL exhibited fast-acting bactericidal efficacy against S. mutans , causing 95.07% death within 5 minutes, compared to CHX (73.33%) ( P <0.01). We observed that 5 mg/mL and 2 mg/mL CNE were both superior to CHX, significantly reducing oral S. mutans numbers and reducing the severity of carious lesions in Sprague Dawley rats ( P <0.05), in an in vivo test. CNE treatment at a concentration of 0.2 μg/mL inhibited biofilm formation more effectively than CHX, as indicated by the crystal violet staining method, scanning electron microscopy, and atomic force microscopy. The cell membrane of S. mutans was also severely disrupted by 0.2 μg/mL CNE, as indicated by transmission electron microscopy. These results demonstrated that CNE greatly improved the solubility and antimicrobial activity of this agent against S. mutans both in vitro and in vivo. This novel nanoemulsion is a promising medicine for preventing and curing dental caries.

Microscopy Methods for Biofilm Imaging: Focus on SEM and VP-SEM Pros and Cons

“…Conventional SEM and FESEM are the best methods for biofilm visualization if high magnification and high-resolution images are needed to accurately describe biofilm morphology [ 50 , 51 , 52 ]. In comparative analyses, like the evaluation of the anti-biofilm effects of a drug/treatment, it appears as an extremely useful tool [ 11 ], since the results of SEM imaging are highly correlated with those from other analytical methods [ 53 , 54 , 55 , 56 , 57 , 58 , 59 ]. The use of dedicated SEM imaging software for biofilm image analysis has allowed for the quantitative morphological analysis of biofilm by several authors [ 56 , 60 , 61 , 62 , 63 ].…”

“…In comparative analyses, like the evaluation of the anti-biofilm effects of a drug/treatment, it appears as an extremely useful tool [ 11 ], since the results of SEM imaging are highly correlated with those from other analytical methods [ 53 , 54 , 55 , 56 , 57 , 58 , 59 ]. The use of dedicated SEM imaging software for biofilm image analysis has allowed for the quantitative morphological analysis of biofilm by several authors [ 56 , 60 , 61 , 62 , 63 ]. The undisputed advantages of SEM and FESEM consist of the combined ability to image with a wide range of magnifications (20 to 30,000×) coupled with high resolution (from 50 to 100 nm) and depth of field.…”

Novel Intravaginal Drug Delivery System Based on Molecularly PEGylated Lipid Matrices for Improved Antifungal Activity of Miconazole Nitrate

“…A modification of the killing rate method described elsewhere [ 46 ] was used. In therapy, as a rule of thumb, clinicians attempt to have peak in vivo antimicrobial levels in tissue that exceed the minimal microbicidal concentration; hence a concentration in each case that is four times the MFC as determined in the preceding section was arbitrarily selected for each sample to examine the kinetics of killing by the optimized SLMs.…”

Immune response effects of diverse vaccine antigen attachment ways based on the self-made nanoemulsion adjuvant in systemic MRSA infection

“…The PdI values were all less than 0.3 (0.184, 0.270 and 0.210), suggesting that all prepared three nanoemulsion formulations exhibit good narrow size distributions. 29 The average zeta potential of the encapsulation, mixture and combination way were À19.60 mV, À21.60 mV and À21.56 mV, respectively, all ranging from À30 to 30 mV ( Fig. 1E and S3B †).…”