Effect of Reaction Temperature on Shape Evolution of Palladium Nanoparticles and Their Cytotoxicity against A-549 Lung Cancer Cells
Authors: Gulam Abbas
Gajanan Pandey
Narinder Kumar
Devesh Kumar
Journal: ACS omega (2019)
Discipline: CHEMISTRY
Keywords: Palladium nanoparticles; synthesis; shapes; sizes; potassium tetrachloropalladinate(II)
Affiliations: Department of Chemistry and Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226025, India.

Abstract:  Palladium nanoparticles (Pd NPs) of different shapes and sizes have been synthesized by reducing potassium tetrachloropalladinate(II) by l-ascorbic acid (AA) in an aqueous solution phase in the presence of an amphiphilic nonionic surfactant poly ethylene glycol (PEG) via a sonochemical method. Materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray soectrscopy (EDX), Fourier transform infrared (FTIR), surface-enhanced Raman spectroscopy (SERS), particle distribution, and zeta potential studies. Truncated octahedron/fivefold twinned pentagonal rods are formed at room temperature (RT) (25 °C) while hexagonal/trigonal plates are formed at 65 °C. XRD results show evolution of anisotropically grown, phase-pure, and well crystalline face-centered cubic Pd NPs at both temperatures. FTIR and SERS studies revealed adsorption of ascorbic acid (AA) and PEG at NP's surface. Particle's size distribution graph indicates formation of particles having wide size distribution while the zeta potential particle surface is negatively charged and stable. The truncated octahedron/fivefold twinned pentagonal rod-shaped Pd NPs, formed at RT, while thermally stable and kinetically controlled hexagonal/trigonal plate-like Pd NPs, evolved at higher temperature 65 °C. The obtained Pd NPs have a high surface area and narrow pore size distribution. To predict protein reactivity of the Pd cluster, docking has been done with DNA and lung cancer-effective proteins. The cytotoxicity of the Pd NPs has been screened on human lung cancer cells A-549 at 37 °C. The biological adaptability exhibited by Pd NPs has opened a pathway in biochemical applications. 

Retracted: No

PubPeer comments:
 In this paper, **Pandey and Colleagues** attempted to investigate the effect of **Pd nanoparticles**. They have synthesized the nanoparticles and carried out detailed physical characterization of the same. The authors have presented sound physical characterization data however, the biological and biochemical characterization seems flawed 1.tAuthors have claimed that, the size of their synthesized particles in the range of **20-50 nm**, however, they have shown its docking inside the DNA double helix structure in the minor grove of the DNA **(Fig11**), which is not possible as it is well known fact that **diameter of the double helix of the DNA is 20 Angstrom (2 nm).** 2.tSimilarly, they have docked it into **several protein structures (Fig 12)** where the details of the dimensions are not available however, similar dimensions mismatch are there as explained in **point#1.** 3.tIt seems, the model of **nano structure (Fig 10)** they are using for the docking etc. is not the structure of the nano particle but this is structure of elemental Pd. 4.tTherefore, authors should remove these results from their analysis as it is highly misleading for the readers. , 
 May I ask the authors how this is proof of  truncated octahedron fivefold twinned pentagonal rodlike Pd nanoparticles ? I can see another structure within it... ![file] , 
 #1 I *think* this is their 40 nm particles in this protein. Also strange about Figure 12 is the legend describes the docking studies as being with an  Ag-Au cluster while the text refers to a Pd nanoparticle. Easy to correct, I m sure. ![file] , 
 #4 What is then  Ag-Au cluster size? Clusters can not fit in couple of angstrom binding pockets present in these proteins. Neither in the groves of the DNA double helix. It is quite unlikely! , 
 #1 I fully agree with Oenochroa Egregia. As the width of the DNA double helix is 2 nm, this is hard to believe. I also am not sure where their evidence for the structure in Figure 10 comes from. Here are the figures so people may see for themselves: ![file] , 
 #4 No, it is not easy to correct, as they have claimed the biological effects are because of NPs, while showing the enzyme inhibition in docking with elemental Pd. Therefore, the work presented is wrong. , 
 #6 We must remember that NPs or NCs made of the same molecules (such as Pd or Ag-Au or anything else) are much larger in size than the molecules themselves. The NPs or Nano clusters are usually constructed up of the repeated units of these molecules, hence these must be of much greater in size. ,