Optimizing Pore Size of CellulosePolysulfone Nanocomposite Microfilms for Hemodialysis

1
Optimizing Pore Size of Cellulose/Polysulfone
Nanocomposite Microfilms
for Hemodialysis

• Background
• The goal of this study is to make stiff and flat
  microchannel membranes that can be used in
  hemodialysis. Existing microchannel devices are
  not optimized for use in dialysis. Current
  dialysis machines remove unwanted solutes from
  the blood through a concentration gradient. The
  patients must go to a hospital three times a week
  for 3-5 hours in order to be treated.
  Microchannel devices are much smaller and thus
  would increase patient comfort. Past studies have
  shown cellulose to be a strong filler material
  (Simonsen 2007). Also natural fillers are useful
  because they have a high specific strength and
  are biodegradable.
• This study will show whether of not it is
  feasible to add cellulose nanocrystals to
  polysulfone microfilms in order to optimize
  efficiency. Four different types of films were
  made using different amounts of polysulfone (Psf)
  and N-methylpyrrolidone (NMP) with a porogen,
  polyethylene glycol (PEG), and a dispersion of
  cellulose nanocrystals (CNXL). The sample
  combinations were chosen based on past studies
  that showed a 5 CNXL concentration to produce
  the strongest films. The amount of PEG was varied
  to test different pore sizes.

• Overview of Films
• All films were white, some having uneven clear
  sections
• Dextrans were not used because pore sizes were
  too large
• All films had water pass through

Riti Gupta and Teresa Chan

• Analysis of Porosity
• Our results were not consistent with our
  hypotheses. The films in sample 1 and 2 were
  white instead of being clear. These films also
  let water through. This means that there were
  pores in these films where past studies have
  shown that the films can be made without pores.
  Samples 3 and 4 both containing the porogen PEG
  let through the most water which is consistent
  with our hypotheses. More water went through
  sample 4 than sample 3 which was stated in our
  hypothesis as well. Since samples 3 and 4 let
  through more water than samples 1 and 2 it shows
  that the PEG did increase the pore size. Our data
  shows that there is a statistically significant
  difference between all the films made except for
  the films made from Sample 2 and Sample 3. These
  two samples are too close in the amount of water
  that came through for there to be any sort of
  conclusion made on the combination used in those
  films. More films would have to be made and
  tested so that a larger set of data could be
  compared.
• The films made in this experiment are not
  optimized for hemodialysis machines. Films for
  hemodialysis must have pores that allows only
  molecules with weights of 3-10 kD to pass
  through. These films have pores much larger than
  that since water passed through easily. Our
  results lead to the conclusion that PEG doesnt
  need to be added because its addition makes the
  pores in the films too large.

2. Films in a water bath.
3. Films were cut in a circle to fully cover the
grooves, and then tested with water.

• Hypotheses
• Solution with 0 CNXL and 0 PEG- Films will be
  clear due to lack of pores. None to a minimal
  amount of water will pass through
• 5 CNXL and 0 PEG- Films will be white. None to
  a minimal amount of water will pass through.
• 5 CNXL and 2.5 PEG- Films will be white due to
  PEG. A small amount of water will pass through.
• 5 CNXL and 5 PEG- Films will be white due to
  PEG. A larger amount of water than the 2.5 PEG
  solution will pass through.

• Methods
• Made solutions for films with Polysulfone (Psf),
  N-methylpyrrolidone (NMP), Polyethylene glycol
  (PEG), and cellulose nanocrystal (CNXL)
  dispersion.
• Evaporated water (Rotavap) from solutions with
  CNXL dispersion since Psf will not dissolve in
  water.
• Cast films on glass plates and placed in water
  bath (75-80C) changed water twice in 24 hours
  to create a concentration gradient and remove NMP
  and PEG.
• Tested individual films by running water through
  them, if little to no water came through, tested
  with dextrans labeled with fluorescent dyes.
• Sample 1 18 Psf, 82 NMP
• Sample 2 5 CNXL, 18 Psf, 77 NMP
• Sample 3 5 CNXL, 2.5 PEG, 18 Psf, 72 NMP
• Sample 4 5 CNXL, 5 PEG, 18 Psf, 67NMP

• Future Research
• Ascertain why our films from Sample 1 (no CNXL or
  PEG) were clear.
• Make solutions with different percentages of PEG
• Make solution with different percentages of CNXL
• Test the strength of the films

Acknowledgements Dr. John Simonsen
Associate Professor, OSU Dr.
Rakesh Gupta
Associate Professor, OSU
Revised 2/11/2008