In recent posts we have tested the total volume of filtrate as a function of time in the centrifuge. We used NPN with different average pore sizes and we studied 100 nm and 20 nm NPs as well as IgG. We showed that while 100 nm NPs were completely blocked 20 nm NPs and the…
In our last post we showed that this latest wafer with 36 nm pores did a better job of blocking 20 nm NPs in the forward and reverse orientations, whereas an older wafer (1070- 45 nm, 15%) showed better separations in reverse orientation. Here is a couple plots summarizing the difference: So 20 nm NPs…
We used chips from the latest 5 slot SepCon NPN wafer 1142 (14%, 36nm) to test our ability to separate 20 nm “blue fluorescent” polystyrene NPs from Invitrogen from IgG. We used a concentration of 10^14 particles/ml NPs and 1 mg/ml IgG. (This is a mixture of fluorescent and unlabeled IgG) We compared forward vs…
In this post we look at the effect of altering the area available for filtration on a standard 5 slot SepCon. Karl and I did this by simply cutting gaskets such that they covered different regions of the surface of a chip. We have three configurations, 1, 3 and 5 slots. Here’s a picture of…
Here’s the paper we’re discussing this week: Wu(Moulin)JMS14 The authors motivate their work by claiming that ultrafiltration membranes can be used to keep “engineered nanomaterials” (ENM) out of our waters. They use confocal laser scanning microscopy to locate the position of fluorescent CdTe quantum dots (QD) on/inside an Ultracel membrane. (Made by Millipore using regenerated…
In this post I’m trying to give a better comparison among filtrations using chips from wafer 1085 using 20 and 100 nm fluorospheres, IgG, and 5 and 20 nm Au NPs. In each slide I try to indicate the flow direction with respect to the membrane. Unless I’ve written “Pressure” near the direction the separations…
We’ve been doing a lot of work characterizing SEPCON performance in forward and reverse configuration. One lesson we’ve learned is that a vertical orientation might be best for high particle concentrations. I discussed this with Greg and he graciously came up with first prototype design. Greg will put is 3D printing experience to work on…
As part of the ongoing study of NPN membrane filtration characteristics I used the SEM to look at membranes after they were used. Unless otherwise indicated, files with a “t” (top) indicate the chip was membrane side up. “b” stands for the bottom, or trench side. In a standard forward centrifuge setup we expect the…
The following plot is an attempt to summarize recent work measuring rate of flow through a membrane as a function of concentration. We investigated 100 nm NPs, (totally blocked), 20 nm NPs (partially blocked) and IgG (mostly passed). In all cases, the buffer used was 1xPBS and 0.1% Tween 20. This plot mostly shows the total…
Our recent work using NPN to separate free IgG from 20 nm NPs has shown that we can pass liquid under either forward or reverse configurations using the centrifuge. We had thought that there would be greater resistance in the forward orientation due to cake layer formation. We had found high resistance to flow in…