title: Enhanced biocidal activity of Au nanoparticles synthesized in one pot using 2, 4-dihydroxybenzene carbodithioic acid as a reducing and stabilizing agent.
abstract: BACKGROUND
  The conjugation of gold nanoparticles with biocides such as natural products, oligosaccharides, DNA, proteins has attracted great attention of scientists recently. Gold NPs covered with biologically important molecules showed significant enhancement in biological activity in comparison with the activity of the free biocides. However, these reports are not very systematic and do not allow to draw definitive conclusions. We therefore embarked in a systematic study related to the synthesis and characterization of biocidal activities of Au nanoparticles conjugated to a wide variety of synthetic and natural biomolecules. In this specific report, we investigated the activity of a synthetic biocide, 2-4, Dihydroxybenzene carbodithioic acid (DHT).
  
  
  RESULTS
  Au nanoparticles (NP) with a mean size of about 20 nm were synthesized and functionalized in one pot with the help of biocide 2,4-Dihydroxybenzene carbodithioic acid (DHT) to reduce HAuCl4 in aqueous solution. Conjugation of DHT with gold was confirmed by FT-IR and the amount of DHT conjugated to the Au nanoparticles was found to be 7% by weight by measuring the concentration of DHT in the supernatant after centrifugation of the Au NPs. To ascertain the potential for in vivo applications, the stability of the suspensions was investigated as a function of pH, temperature and salt concentration. Antibacterial, antifungal, insecticidal and cytotoxic activities of the Au-DHT conjugates were compared with those of pure DHT and of commercially available biocides. In all cases, the biocidal activity of the Au-DHT conjugates was comparable to that of commercial products and of DHT.
  
  
  CONCLUSIONS
  Since the DHT concentration in the Au-DHT conjugates was only about 7%, our results indicate that conjugation to the Au NPs boosts the biocidal activity of DHT by about 14 times. The suspensions were found to be stable for several days at temperatures of up to 100°C, salt concentrations up to 4 mol/L and a pH range of 2-13.
authors.forename: Syeda Sohaila
authors.initials: SS
authors.lastname: Naz
authors.forename: Nazar Ul
authors.initials: NU
authors.lastname: Islam
authors.forename: Muhammad Raza
authors.initials: MR
authors.lastname: Shah
authors.forename: Syed Sartaj
authors.initials: SS
authors.lastname: Alam
authors.forename: Zafar
authors.initials: Z
authors.lastname: Iqbal
authors.forename: Massimo
authors.initials: M
authors.lastname: Bertino
authors.forename: Louis
authors.initials: L
authors.lastname: Franzel
authors.forename: Afifa
authors.initials: A
authors.lastname: Ahmed
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001156:Artemia / Q000187:drug effects; D001419:Bacteria / Q000187:drug effects; D005658:Fungi / Q000187:drug effects; D006046:Gold / Q000737:chemistry / Q000494:pharmacology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D050296:Microbial Viability / Q000187:drug effects*; D010316:Particle Size; D010575:Pesticides / Q000737:chemistry / Q000494:pharmacology; D012965:Sodium Chloride; D013859:Thiocarbamates / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D010575:Pesticides; D013859:Thiocarbamates; D012965:Sodium Chloride; D006046:Gold