title: Mixed metal oxide nanoparticles inhibit growth of Mycobacterium tuberculosis into THP-1 cells.
abstract: OBJECTIVE
  Humans have been in a constant battle with tuberculosis (TB). Currently, overuse of antibiotics has resulted in the spread of multidrug-resistant Mycobacterium tuberculosis (MDR), leading to antibiotic ineffectiveness at controlling the spread of TB infection in host cells and especially macrophages. Additionally, the Mycobacterium tuberculosis (Mtb) has developed methods to evade the immune system and survive. With the discovery of nanoparticle (NP)-based drugs, it is necessary to research their anti-mycobacterial properties and bactericidal mechanisms. In this study, we synthesized mixed metal oxide NPs and tested their ability to inhibit Mtb growth into macrophages and investigated the cytotoxic effects of NPs in THP-1 cells.
  
  
  METHODS
  Silver (Ag) NPs and zinc oxide (ZnO) NPs were synthesized by chemical reduction and chemical deposition in aqueous solution, and the diffraction light scattering, scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible light-absorption spectra were used to identify NP properties. Ag and ZnO NPs were mixed together at a ratio of 8ZnO/2Agand diluted into Löwenstein-Jensen medium followed by the addition of bacteria and incubation for 28days at 37°C. The toxicity of NPs to THP-1 cells was assessed by MTT test, and macrophages were infected with Mtb for 4h at 37°C under 5% CO2.
  
  
  RESULTS
  Nano-sized particles were estimated at ∼30-80nm, and the initial concentration of Ag NPs and ZnO NPs were estimated at ∼20ppm and ∼60ppm. The minimal inhibitory concentration ratio of 8ZnO/2AgNPs against Mtb was detected at ∼1/32 of the initial concentration. Ag NPs in the range of concentrations exhibited no anti-Mtb effects, whereas ZnO NPs showed potent antibacterial activity at ∼1/128 of the initial concentration. ZnO NPs at all concentrations showed cytotoxic activity, whereas 100% of THP-1 cells remained viable in the presence of Ag NPs at ∼1/32 and ∼1/64 of the initial concentrations. However, at ratios of 8ZnO/2Ag, ∼39.94% of the cells at ∼1/16 of the initial concentration remained viable, with 100% of THP-1 cells at ∼1/32 of the initial concentration remaining viable.
  
  
  CONCLUSIONS
  Although Ag NPs exhibited low cytotoxicity, they were unable to inhibit Mtb growth in vitro. ZnO NPs exhibited strong anti-Mtb activity and inhibited bacterial growth, but exhibited high cytotoxicity to human macrophage cells. By mixing Ag and ZnO NPs at a ratio of 8ZnO/2Ag, we acquired a mixture that exhibited potent antibacterial activity against Mtb and no cytotoxic effects on THP-1 cells, resulting in inhibition of both in vitro and ex vivo Mtb growth Figs. 1-3, Tables 1-3.
authors.affiliation: Rasoul-e-Akram Hospital, Antimicrobial Resistance Research Center, Iran University of Medical Sciences, Tehran, Iran. Electronic address: jafari.ar@iums.ac.ir.
authors.forename: A R
authors.initials: AR
authors.lastname: Jafari
authors.affiliation: Rasoul-e-Akram Hospital, Antimicrobial Resistance Research Center, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: T
authors.initials: T
authors.lastname: Mosavi
authors.affiliation: Razi Vaccine and Serum Research Institute, Karaj, Iran.
authors.forename: N
authors.initials: N
authors.lastname: Mosavari
authors.affiliation: Rasoul-e-Akram Hospital, Antimicrobial Resistance Research Center, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Majid
authors.affiliation: Department of Medicinal Chemistry and Pharmacology, Institute for Tuberculosis Research, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: F
authors.initials: F
authors.lastname: Movahedzade
authors.affiliation: Razi Vaccine and Serum Research Institute, Karaj, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Tebyaniyan
authors.affiliation: Razi Vaccine and Serum Research Institute, Karaj, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Kamalzadeh
authors.affiliation: Razi Vaccine and Serum Research Institute, Karaj, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Dehgan
authors.affiliation: Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Jafari
authors.affiliation: Department of Microbiology, Faculty of Basic Sciences, Islamic Azad University, Qum Branch, Iran.
authors.forename: S
authors.initials: S
authors.lastname: Arastoo
keywords: Mycobacterium tuberculosis; Nanoparticles; THP-1 cells