I have results about the decrease of Candida albicans adherence in some biomaterials when using the spherical shape. Using prisms or disks there is no antifungal effect.
Could it be due to the surface area of the different nanoparticles? What are the dimensions of each?
Could it be due to the surface area of the different nanoparticles? What are the dimensions of each?
I am agree with Omar Lozano. What happen whether we have the same surface but different geometry? The fungis needs have point of attachment on the silver surface.
Hello,
I agree with Omar.
The antimicrobial effect of Ag is usually a consequence of (i) oxidation of Ag atoms on the surface of the NPs and subsequent interaction of Ag+ ions with cell walls, or (ii) due to acute toxicity caused by the accumulation of Ag NP in cells.
Therefore, for (i) the antimicrobial activity will increase with an increase in surface-to-bulk atom ratio = decrease in particle size, also any molecules on the surface of your Ag NP will decrease the am activity further. I do not know about your case, but usually disks/triangles are larger than spheres and also have a templating agent like CTAB on their surfaces. If that is the case, the antimicrobial activity of non-spherical should be less pronounced. The only situation in which for example disks/triangles could exhibit higher am activity is when a close packed surface (for example (1 0 0)) is on the flat side due to higher number of atoms.
For (ii), smaller particles will internalize cell more easily than the larger ones. So, in this case, the size matters.
Hope this helps!
D.
I agree as well; the shape may not be crucial but the total surface; the spherical nanoparticles might be smaller. What is the respective particle size of each of these particles?
Thank you for all your comments ¡¡¡
Here the information about the dimensions of my particles:
Shperical particles are 10-20 nm
Prism particles = 100 nm
Disks particles = 25 nm
What is the # particles per unit area? Maybe everyone is correct but because the amount of surface area per unit volume of spherical particles is highest per ml than the others?
surface density is important AND remember that the smaller the NPs are, the easier they dissolve too and the more easier they can enter bacterias etc
Laura, with the particle size (and density) you can easily calculate the surface area per gram, and you will be surprised how much even the difference is between 10 and 25 nm (not to talk about 100 nm ...) Please calculate yourself and let us know your results!
:-)
More symmetrical distribution of Ag atoms around the NP may be one of the reason.
The surface area per unit volume of a sphere is 6/d where d is the diameter of the particle.Thus for spherical nano-particles the surface area per unit volume would be large (as d is very small ) and it will contribute to its anti-fungal activity by noncompetitive inhibition of fungal enzymes.
.
I would like to specify that the larger surface area in the spheres is due to the size, and not to the shape. In fact, from all the possible geometries, the spheric has the smallest surface area per unit volume.
That said (maybe many people will already know it, but I just want to make it clear), if all the nanoparticles had the same volume the spherical ones would be the less effective (assuming that anti-fungal nature of the nanoparticles depends only on the surface area).
By the way, if they are not in suspension, the reactivity of the disks may be way smaller than it could, because the disks would fall flat on the surface on which they are (let's call it "the floor") and the half of their surface touching that "floor" would not be exposed to react with the fungi, so only half of their total surface would perform as anti-fungal.
sure, I assume we all know this, but the particles which Laura used not only had different shape, but also very different size. Therefore, the surface area will be very different! (and that is what I suggested her to calculate by herself: what is the specific surface area per g for the various nanoparticles they used)
For having a comprehensive answer for this question and any other questions related to this, I think you may want to read this paper:
The Effect of Nanoparticle Size, Shape, and Surface Chemistry on Biological Systems, Alexandre Albanese, Peter S. Tang, andWarren C.W. Chan, Annu. Rev. Biomed. Eng. 2012. 14:1–16.
The spherical nanoparticle will have higher surface area compared to prism and triangular morphology . So charge density will be more in spherical. Also the transverse and longitudinal phase is same for spherical but for the disk and prism will be having two phases, which can be differentiated with the color of our nanoparticle.
sorry, Rohit, this I would not believe without having seen evidence. Do you have any literature reference for that?
I think the effect which was observed is "simply" due to the much high surface area which the (in this case much smaller) spherical nanoparticles are offering.
but in this case the spherical ones had the bigger effect! and - as far as I can see from distance - in the case we are discussing here, the spherical particles are MUCH smaller, hence they have the MUCH bigger specific surface area to deliver Ag to the cell.
The situation would be very different, if the same or at least comparable specific surface area would be offered: same / similar surface area for spherical and prisms. Then something else comes into play:
prisms, discs, triangular shaped particles have edges, tips, the spherical ones don't. Such edges / tips have a MUCH higher surface tension and hence a much higher reactivity.
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