TABLE 3.

Application of metallic nanoparticles against Streptococcus spp.

Metal	Synthesis method		Bacteria	Highlights	References
Silver	Green synthesis	Terminalia mantaly extract	S. pneumoniae	The biogenic Terminalia mantaly-Ag NPs showed significant antibacterial activity compared to the respective extracts	Majoumouo et al., 2019
		Allium cepa and Allium sativa extract	S. pneumoniae	AgNPs exhibited antibacterial activity against selected vaginal bacteria	Bouqellah et al., 2019
		Fruit extract of Prosopis farcta	S. pneumoniae	AgNPs increased the antioxidant and antibacterial activity compared with the extract alone, due to high content in phenolic compounds.	Salari et al., 2019
		Tapinoma simrothi	S. pyogenes	AgNPs with effective antimicrobial activity in a wide range of bacteria	Sholkamy et al., 2019
	Chemical synthesis	Silver nitrate reduced by sodium borohydrate	S. pyogenes	AgNPs as carrier of new quinazolinone compounds showed enhanced antibacterial activity	Masri et al., 2019a
Gold	Green synthesis	Justicia glauca extract	S. mutans	AuNPs coated with antibiotic increased efficacy against a broad range of bacteria	Emmanuel et al., 2017
		Resveratrol as a green reducing agent	S. pneumoniae S. pyogenes	AuNPs-resveratrol increased efficacy against S. pneumoniae compared to resveratrol	Park et al., 2016
	Chemical synthesis	Reduction of gold (III) chloride trihydrate by sodium citrate	S. pneumoniae	Uptake of AuNPs by S. pneumoniae associated the antibacterial activity to the formation of inclusion body of AuNP (IB-AuNPs), composed by proteins, carbohydrates and lipids. Some proteins associated with IB-AuNPs could be used for new strategies	Ortiz-Benítez et al., 2019
		Citrate reduction of gold (III) chloride trihydrate	S. mutans	Combination of AuNPs and diode irradiation decreased CFUs	Sadony and Abozaid, 2020
Gold-silver	Gold-silver nanocages via galvanic replacement reaction		S. mutans	Au-Ag nanocages promoted the inhibition of S. mutans	Wang et al., 2016
Gold-titanium	Commercial TiO2 nanotubes with Au via direct current plasma sputter		S. mutans	Ti nanotubes sputtered with Au nanorod irradiation increased the inhibitory effect against S. mutans	Moon et al., 2018
	Green synthesis: Terminalia chebula bark extract		S. pneumonia	Au-TiNPs loaded with carbon nanotubes and irradiated under visible light showed higher antimicrobial activity than ampicillin	Karthika and Arumugam, 2017
Zinc-silver	Polymeric precursor and coprecipitation		S. mutans	Zn-AgNPs inhibit S. mutans biofilm formation (dentistry)	Dias et al., 2019
Iron	Green synthesis	Agrewia optiva and Prunus persica extracts	S. mutans S. pyogenes	FeNPs provided antimicrobial activity and antioxidant capacity associated to compounds from extracts	Mirza et al., 2018
	Chemical synthesis	Commercial NPs	S. mutans	Chitosan coated FeNPs as carrier for chlorhexidine; bacteria eradication and antibiofilm effect	Vieira et al., 2019
		Ferric chloride and ferrous chloride tetrahydrate	S. mutans	FeNPs on surface for eradication of S. mutans	Javanbakht et al., 2016
		Solvothermy employing iron (III) chloride	S. mutans	Vitamin B2 coated FeNPs promoted antibacterial activity	Gu et al., 2020
Copper	Chemical methods: copper acetate as precursor		S. mutans	Hybrid Cu-chitosan NPs reduced MIC and minimum bactericidal concentration	Covarrubias et al., 2018
	Commercial NPs		S. mutans	CuNPs added to orthodontic composite inhibited the growth of S. mutans	Toodehzaeim et al., 2018
Zinc	Zinc acetate dihydrate as precursor		S. pneumoniae	ZnNPs reduced IMC and showed anti-biofilm formation activity	Bhattacharyya et al., 2018
	Green synthesis: Costus igneus extract as capping and reducing agent		S. mutans	ZnNPs showed a dose dependent antibacterial and antibiofilm effect against S. mutans	Vinotha et al., 2019