Promising biocidal activity of thymol loaded chitosan silver nanoparticles (T-C@AgNPs) as anti-infective agents against perilous pathogens
Authors: H N Naveen Kumar
H M Manukumar
S Umesha
Journal: International Journal of Biological Macromolecules (2017)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Chitosan; T-C@AgNPs; Thymol.
Affiliations: Department of Studies in Biotechnology, University of Mysosre, Manasagangotri, Mysuru 570006, Karnataka, India., Department of Studies in Biotechnology, University of Mysosre, Manasagangotri, Mysuru 570006, Karnataka, India. Electronic address: ., Department of Studies in Biochemistry, Kuvempu University, Shankarghatta, Shimoga, Karnataka, India.

Abstract:  The advent of biodegradable polymer-encapsulated drug nanoparticles has made an exciting area of drug delivery research. The present study investigated novel and simple route for synthesis of thymol loaded chitosan silver nanoparticles (T-C@AgNPs) using chitosan and thymol as reducing, capping agent respectively to understand the therapeutic efficacy. The UV-vis spectroscopy, DLS, FT-IR, SEM, EDS, XRD used for characterization and radical scavenging activity, anti-microbial and biocompatibility was taken to ascertain an efficacy of novel T-C@AgNPs. The T-C@AgNPs intense peak at 490nm indicates the formation of nanoparticles and had average particle size of 28.94nm with spherical shape, monodisperse state in water, also exhibited excellent biocompatibility of cubic shaped pure silver element containing T-C@AgNPs. The antibacterial activity was studied for gram positive and gram negative food-borne pathogens and effective inhibition at 100μgmL-1 to S. aureus, S. epidermidis, S. haemolyticus (10.08, 10.00, 11.23mm) and S. typhimurium, P. aeruginosa and S. flexneri (9.28, 9.33, 12.03mm) compared to antibiotic Streptomycin. This study revealed the efficacy against multiple food-borne pathogens and therapeutic efficacy of T-C@AgNPs offers a valuable contribution in the area of nanotechnology. This proved to be a first-class novel antimicrobial material for the first time in this study. 

Retracted: No

PubPeer comments:
 What took me aback as I was going through this publication are the following: ![file] Figure 5: If you take a close look at the magnification level (x2.00K or simply x 2000), gratings representing 20u00b5m on the main image, plus the expanded image at x8.00k or x8000 magnification and scale denoting 5u00b5m; a simple comparison shows that the highlighted spherical structures are roughly 2 to 2.5u00b5m in diameter and not 28.94 nm as mentioned in the publication. Further read-through of the article reveals the following observations: A discrepancy in nanoparticle preparation methodology-section 2.2 (below) and the description below figure 1 (below). Which is the correct version? ![file] ![file] Thymol solution appears rather clear in figure 1, while in figure 2 (below) it has significant absorbance within the lower visible range (green curve). The purple spectrum of chitosan silver nanoparticles (C@AgNP) shows a peak within the UV range (around 300nm). Based on observations in many publications on silver nanoparticles, a monodisperse colloid of AgNPs with an average diameter of 28.94nm would normally have a spectrum with an almost bipolar symmetrical SPR peak at some point around 400nm. The shape of the silver nanoparticle dispersions absorbance spectrum is rather unusual too. ![file] Table 1: In section 2.7 of Materials and methods (below) it is stated u201cu2026.then sterile disc (6 mm) was loaded 5u00b5L of different serial dilutions of T-C@AgNPs (10, 20, 30, 40, 50 and 100 u00b5g discu22121) were addedu2026u2026u201d However, the headings of T-C@AgNPs concentration in tabulated data and statements in section 3.5 of the discussion give concentration in u00b5g mlu22121. ![file] ![file] Above is a brief of the noted inconsistencies. Similar concerns would then arise in the article below by the same group u201cNovel T-C@AgNPs mediated biocidal mechanism against biofilm associated methicillin-resistant Staphylococcus aureus (Bap-MRSA) 090, cytotoxicity and its molecular docking studiesu201d DOI: 10.1039 C7MD00486A Note similarity of the images and bar scale modification (circled in red) for Fig 1 in DOI: 10.1039 C7MD00486A (Below) ![file] The investigations described in the publications are anchored on the synthesized nanoparticles. Could the authors comment on research articles? ,