title: 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.
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Yun Fei
authors.initials: YF
authors.lastname: Li
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Hong Wu
authors.initials: HW
authors.lastname: Sun
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Biomedical Engineering, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Gao
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Kai Yun
authors.initials: KY
authors.lastname: Liu
authors.affiliation: Wanzhou Institute for Food and Drug Control of Chongqing, Wanzhou, Chongqing, People's Republic of China.
authors.forename: Hua Qi
authors.initials: HQ
authors.lastname: Zhang
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Qi Huan
authors.initials: QH
authors.lastname: Fu
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Sheng Li
authors.initials: SL
authors.lastname: Qing
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Gang
authors.initials: G
authors.lastname: Guo
authors.affiliation: National Engineering Research Center of Immunological Products, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China ; Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University of Chinese PLA, Chongqing, People's Republic of China.
authors.forename: Quan Ming
authors.initials: QM
authors.lastname: Zou
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D018441:Biofilms / Q000187:drug effects*; D003731:Dental Caries / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control; D004655:Emulsions / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D049329:Nanostructures / Q000737:chemistry / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D013295:Streptococcus mutans / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D004655:Emulsions
keywords: Streptococcus mutans; antibacterial; chlorhexidine acetate; nanoemulsion