Aim: Preparing cellulose solutions to be spread on the support, perform different concentration tests.
The cellulose being an integral part of the patch, we need to determine different solubility levels in order to constitute the correct mix for forming a solid support.
Manipulation:
• cellulose solution in water and ethanol
• cellulose used = carboxymethyl-cellulose (CMC)
• Total volume = 40 ml solutions -> 40 g precisely (final weight)
Cellulose solutions in water :
Solution
% weight referred
m (cellulose) referred (g)
m final 5 (g)
m water added
(1)
1.25
0.5
0.548
40.162
(2)
2
0.8
0.818
39.541
(3)
3
1.2
1.216
40.401
(4)
5
2
2.052
38.305
(5)
10
4
4.029
36.192
(6)
15
6
6.099
35.179
(7)
20
8
/
/
Table 1: Masses
N.B: Given the excessive viscosity of the 15% to 20% solution was not prepared. Solution of cellulose in EtOH:
2% by weight referred, 0.8 g referred cellulose. → 0.828 g of cellulose weighed; final weight Total: 35.317 g -> 2.3% These solutions were prepared in a 50 ml glass beaker covered with plastic film and left under magnetic stirring overnight at room temperature. In the different EtOH solutions → pure EtOH does not dissolve: solutions dissolve well for below 10% but are not homogeneous when content reach15%.
Conclusion/ Results:
EtOH does not dissolve the cellulose, H20 is the best solvent. → The solutions below 10% are homogeneous, but above 15% they are not (it is too viscous).
May 26, 2016:
Spreading test solutions of cellulose on different supports:
Aim: Determine the solid support on which the spreading of the cellulose solution is optimal in view of evaporation of the solvent. The cellulose based patch needs to be created out of the dissolved cellulose solutions; in order to do that the solvent needs to be evaporated by spreading the mix over a solid support.
Principle: Spreading on media, qualitative evaluation of substrate wetting, and evaporation.
Manipulation: Spread with a flat spatula and qualitative assessment of the dampening (flexibility of the constituted solid surface).
With 3% solution:
• with glass: very little grip, grainy materail that are not separated by spreading.
• with paper filter: moderately satisfactory result, good flow, good adhesion but the filter paper is soaked.
• with aluminim: it spreads well in the beginning but dry very quickly and becomes granular in a few seconds.
• with a PVC film: same as glass with less ease of spreading.
With 1.25% solution:
• with aluminum: a result slightly better but with holes that are always formed, the material dries.
• with the filter paper: a result a little better, good flow.
• with PVC: same.
• with glasses: same.
Problem: The glass and aluminum does not give quite satisfactory results.
With the 5% solution:
Same with the glass and aluminum → easier spreading at the beginning then more difficult because of the surface tension, but with a slower reaction because of the higher viscosity. 5% on normal paper: good texture after wetting, good flow, low drying. The most effective materials are aluminum and the filter paper.
Plate making test: spread then put in an oven at 50 °C: Test plates:
The solutions were spread through a calibrated wiper system to the surface is as flat as possible a layer. The plates are placed in an incubator 50 °C for 20 hours. Another test has been performed: on a glass plate in a 10% solution that has been deposited on cotton and the plate is placed in an oven.
Results of drying in the oven: Cellulose deposits are invisible on paper. Even scratching does not cause the cellulose grain to coming off. On aluminum, 10% solution of cellulose gave some stuck grains that couldn't be removed by scratching. Conclusion: The cellulose concentration is too low.
The deposit on cotton gave an unexpected result: the solution solidified into a flexible film. The surface is uneven and therefore of little use for our patch. To try to obtain a homogeneous film, several other experiments are conducted. → The 10% solution is placed between two glass plates and then placed in an oven → Another plating on aluminum is done. To avoid the wetting phenomenon which makes the convex surface, the walls were made by inserting the foil in a rectangular mold. Two tests are performed:
• The foil is filled with a 10% solution
• The foil is filled with a 10% solution and some cotton fibers are added over the paper. If the result is a film, the planar surface would be one that is below (where there is no cotton fibers). These plates are dried in open air for 5 days as an oven is unavailable.
Testing a mixture of solvent: water-ethanol.
Aim : Dissolving cellulose in a water-ethanol mixture to use the fact that these two species form an azeotropic mixture.
Evaporating the mixture, ethanol will leave more easily than water, which will increase the cellulose concentration in water and bring it to solidify.
One must test x % EtOH that is less than 90%, such that more ethanol will evaporate, thus forcing the cellulose to solidify more. Two solutions are prepared:
• xetOH = 50%
• xetOH = 70%
Unfortunately, these solutions do not dissolve cellulose. So the deposit appears to be too heterogeneous for sedimentation; it would result in basically unequal amounts of cellulose. Conclusion: the water-ethanol mixture behaves like the ethanol solution.
May 27, 2016:
Compression of the powder or a powder-water mixture to make the patch.
Aim:
Produce a patch with pure cellulose powder to avoid the problem of too low concentration. After the difficulties with the water/EtOH_Cellulose mixtures, we decided to use pure cellulose in a compressed form.
Principle:
Compress the powder to assess the surface produced by such method. The shape of the patch is given by a mold used in the pressor compartment.
The powder is first compressed into a rectangular mold 1 mm thick at 200 bar and at room temperature. The result is quite satisfactory: a friable solid is obtained. To harden the materiel obtained, the same experiment is conducted by adding a few drops of water on top. After compression, the powder was solidified in part and a few grainy bits remained. It is therefore necessary to mix water and the powder before compressing. A water-cellulose mixture is then prepared: 3.42 g of cellulose and 3 g of water.
It gives a mixture of 53% cellulose. It has a paste like texture. The compression plates have been heated beyond our control. We proceeded with cutting the shapes are by lack of time. The only powder is compressed into a mold in the form of 0.5 mm thick test piece. plate temperature is 90 °C. The result is the same, a brittle solid. The mixture at 53 °C cellulose is then compressed at 80 °C in the same mold. A flexible and resistant film is obtained. It is a bit transparent. The patches obtained are then immersed in water in order to simulate for the reaction of the patch to the incorporation of proteins and to the silification.
We observed that after 1 minute 45 s, the patch from the cellulose-water mixture softens but doesn't disaggregate. It can be recovered in a solid form. After 2 min, the patch from the cellulose only (without water) powder curves but remains strong.
The patches are then allowed to dry in the open area. Conclusion: This method is suitable for manufacturing. It remains to determine how to incorporate protein and silica.
May 28, 2016:
Improvements
Aim: Improve cellulose patch and drying results. We have pursued the testing of the patches for mechanical properties and for resistance to water in order to mimic the conditions that would be faced in the presence of protein solutions.
Results of drying after immersion patches of May 27, 2016:
Both patches have hardened to give a patch that holds itself (good mechanical properties). One obtains a similar result to a higher concentration of water patch. → We keep the mechanical strength after immersion and drying. This result is similar to the texture we are looking for our patch.
Paper cups drying aluminum
Result:
• Heterogeneous deposit and fines in the mold without cotton fibers.
• The one with the cotton fibers has given a rigid film thus a fixed cotton-cellulose composite and shows added mechanical strength.
June 3, 2016:
Preparation of other patches:
Aim: Produce patches with the cellulose powder by testing other cellulose concentrations, and other temperatures. We would like to explore other conditions for formong the patches, thereore we plan other experiments including other ratios of water:cellulose, pressures and temperatures.
Principle: Compress the powder (with water optionally) with a press for discharging air in the cellulose powder, or for expelling excess water. The shape of the patch is given by a mold.
Manipulation: • Preparation of a 75% paste, composed of 4.5 g of cellulose + 1.5 g of water → Paste A • Preparation of another pulp 75%, 4.5 g cellulose + 1.5 g of water → Paste B • Preparation of a pulp 65%, 3.9 g cellulose + 2.1 g of water → Paste C
• Compression of the Paste A to 200 bar at room temperature (2 min). We obtained an opaque patch, some areas have dried, there is a good mechanical strength, not too brittle.
• Compression of the Paste B to 200 bars at 70 ° C (2 min). We obtained a patch with interesting properties: it has intermediate mechanical properties, smooth, more rigid than that at 65% and 53%; however, it is somewhat brittle.
• Compression of the Paste C to 200 bars at 70 ° C (2 min). A translucent patch is obtained, flexible, almost identical to Paste B.
Conclusion: The pulp at 75% cellulose seems to have given the most interesting result for its mechanical properties and its apparent homogeneity before and after immersion / drying. The temperature of 70 °C seems well suited to the specifications of the patch.
July 7, 2016:
Compression of new patches with Kapton tape:
Aim: Make new patches bu using Kapton tape (adhesive coating, Dupont) to strengthen them. Test different concentrations, temperatures, and types of cellulose. (+ influence of a protein on compression). We need a solid surface on which to lay our cellulose patching fabrication. After testing paper, cotton, aluminum and plastic, we will test Kapton, which is used as a tape in spacecraft industry.
Principle: Compression of microcrystalline cellulose powder with a press to evacuate air. The shape of the patch is given by a mold.
Manipulation:
• Preparation of two 100% cellulose patches to determine the actual weight of powder required to make a patch (2 types of cellulose: Avicel and Sigmacell- 50 µm crystal MCC)
Patch n°:
1) 100% Sigmacell, 200 bars, 2 min, RT, Kapton tape
2) 100% Avicel, 200 bars, 2 min, RT, Kapton tape
N.B.: 3 g of powder are required to make a patch (2 g display)
• Preparation of two patches (one with a protein and another without) to determine whether a protein has an influence on compression.
Solution of protein: 3 mg of BSA (Bovine Serum Albumin) in 1 ml of distilled water.
2 patches:
3) 50% (1 g cellulose + 1 ml BSA solution at 3 mg/ml), Sigmacell, 200 bars, 2 min, RT, adhesive Kapton
4) 50% (1 g cellulose + 1 ml water), Sigmacell, 200 bars, RT, adhesive Kapton, 2 min.
→ The presence of protein doesn’t change anything anything to the mechanical properties of the patch.
We can therefore proceed with the experiment the point when well will need to add our protein to the patch.
Aim: We need to start again this experiment since the protein wasn’t in a buffer (Tris, NaCl)→hydrophobic parts aggregate → which may lead to phase separation. We neede to test this environment for the protein, as unlie BSA which behave moderately well in distilled water, we have to anticipate that or protein construct which will be a fusion protein, might require a buffer to keep it in a stable state.
Preparation of several patches to test concentration:
w/w %
Cellulose weight (g)
Water weight (g)
60
1.8
1.2
70
2.1
0.9
80
2.4
0.6
90
2.7
0.3
Table 2: Quantities
Patch n°:
5) 60% Sigmacell, 200 bars, 2 min, RT, Kapton tape
6) 70% Sigmacell, 200 bars, 2 min, RT, Kapton tape
7) 80% Sigmacell, 200 bars, 2 min, RT, Kapton tape
8) 90% Sigmacell, 200 bars, 2 min, RT, Kapton tape
9) 50% Sigmacell, 200 bars, 2 min, RT, Kapton tape
10) 60% Sigmacell, 200 bars, 2 min, RT, Kapton tape
11) 70% Sigmacell, 200 bars, 2 min, RT, Kapton tape
12) 80% Sigmacell, 200 bars, 2 min, RT, Kapton tape
13) 90% Sigmacell, 200 bars, 2 min, RT, Kapton tape
→ The best concentration appears to be 70% w/w for homogeneity, mechanical resistance…etc
• Below 70%, the patch contains too much water on cellulose doesn’t stick to the tape
• Above 70%, the patch is too dry, it crumbles
• Test with 2 layers of Kapton tape:
14) 2 x (200 bars, 2 min, RT) 2 Kapton layers, 70%
→ good mechanical properties, but it still crumbles between the 2 Kapton layers silica required!
• Test with 2 layers of Kapton tapes at different temperatures
15) 2 x (200 bars, 2 min, 50°C) 2 Kapton layers, 70%
16) 2 x (200 bars, 2 min, 80°C) 2 Kapton layers, 70%
→80°C: still crumbling, white (and not transparent like the one with carboxymethyl cellulose)→water evaporated
→50°C: good, still water, homogeneous.
Conclusion: The best patch seems to be the double layered, 50°C, 70% w/w one.
However, we must find how to get the properties and the flexibility of carboxymethyl cellulose (CMC) 65°C patch (200 bars, 80°C)
Picture 1-Sigmacell cellulose patches
Picture 2- Avicel cellulose patches
• Avicel patches are better (crumble less, better cohesion)
• The more water there is, the less Kapton tape is efficient to stick cellulose powder.
Picture 3- Kapton double layered patches
→ flexible
→transparent
→homogeneous
July 22, 2016:
Test of the feasibility of the detection device with Coomasie blue
Aim: See if it is possible to use Coomasie blue to reveal the presence of the viral protein. Our aim in this experiment is to evaluate the amount of protein retained on the cellulose layer. We will use the capacity of Coomassie blue to stain proteins (lysine, arginine) in order to estimate the amount bound.
Principle: Pour Coomasie blue on the patch and wash it with water.
Experiment:
• The Coomassie blue was poured on the 65% carboxymethyl cellulose (CMC) and then, the patch was washed.
• Washing the patch during around 15 seconds was enough to significantly remove the color.
• The same experiment is carried out on the patches 12, 11 and 9
Washing the patch during several seconds is not enough to remove the color
They are immersed in water for decoloration during 30 min.
We need to improve this method of estimation of the amount of protein bound. One other method is to soak the patch in a solution of known protein concentration, followed by the estimation of the amount of protein left after the patch has been removed. We plan to use the Bradford assay, using a standard curve based on BSA fo rthis experiment.
Compression of new patches (without Kapton tape)
Aim: Make new patches without Kapton tape. Test different temperatures and types of cellulose. Obtain the same flexibility and homogeneity as with the CMC patch (65%, 80°C, 200 bars).
Principle: Compression of microcrystalline cellulose and CMC powder with a press to evacuate air. The shape of the patch is given by a mould.
Experiments: CMC= carboxymethyl cellulose
• Preparation of the same CMC patch: (2.1 g cellulose / 0.9 g eau) 70%, RT, 2 min, bars, CMC (fig1)
→The patch is flexible, homogeneous and transparent (we reached the expected result, this method is reproducible). This process works at room temperature great!
• Preparation of the same CMC patch with BSA/buffer
- dissolution of 3 mg of BSA in 0.9 g of Tris/HCl buffer
- mix with 2.1 g of CMC
- compression: 200 bars, RT, 4min (with BSA) (fig 2)
→ We got a patch with a good flexibility but it’s not very homogeneous
• Preparation of an Avial patch : 70% RT, 4min, 200 bars, Avial (fig3)
→ We got a white opaque, brittle patch, easily crumbled
• We tried to increase the temperature of the press to get the same patch with Avial as the one with CMC.
- Avial, 50°C, 4min 200 bars, 70% (fig5)
- Avial, 80°C, 200 bars, 70% (fig 6)
→ At 80°C, the patch is more solid.
→ We do not succeed in making a flexible and transparent patch, neither at 50°CC nor at 80°C, with CMC.
The stiffness of the patches increases as they dry (true for all the patches).
Fig1/Fig2/Fig3/Fig4/Fig5/Fig6
Patches prepared on July 22, 2016
October 7, 2016:
Test of binding protein-patch
Aim: Prepare various patches with the silicated C2 protein in them, for immuno-assays and traction tests.
Materials:
• Avicell commercial cellulose
• Silicated C2 protein from previous weeks
• Scale and a press
Protocol: see the patch compression protocol
Experiment:
We prepared:
• a 100% Avicell patch
• a 100% CMC patch
• a 10mm diameter patch with 66%wt of Avicell: 50mg of silicated C2 protein + 100mg of Avicell
• a 10mm diameter patch with 66%wt of CMC: 50mg of silicated C2 protein + 100mg of CMC
• ten 3mm diameter patch with 50%wt of Avicell: 50mg of silicated C2 protein + 50mg of Avicell
• ten 3mm diameter patch with 66%wt of Avicell: 50mg of silicated C2 protein + 100mg of Avicell
