Week 5

Post-Interview and Class Notes: Notes on Interview with Dr. Kara Spiller

• Divalent ion can cross-link sodium alginate
• Ca²⁺ is ideal because the negatively charged groups of sodium alginate can bind on either side of it, forming ladder-like cross-links (pictured below)

http://www.rsc.org/learn-chemistry/wiki/Expt:Cross-linking_polymers_-_alginate_worms

• More cross-links à stiffer hydrogel that does not swell as much
• Creating a hydrogel film:
• Inject sodium alginate and ibuprofen solution between two sheets held together at a specified width
• Dunk this in a calcium solution
• Allow calcium solution to diffuse throughout the sodium alginate (length of time?)
• Factors to consider/test:
• Calcium concentration – vary and test resulting consistencies (tensile testing?)
• Measure swelling as a measure of degree of cross-linking
• Put hydrogel in PBS
• Take reading (every 5 minutes?) of concentration of ibuprofen in PBS using UV spectroscopy (check if UV range of plate reader is fixed, if not, use UV spectrometer available, possibly from biology lab)
• Possible alternative for testing/prototype purposes: find model drug that is a dye with a similar structure to ibuprofen (easier to test with spectroscopy)
• New constraint to consider – over-hydrating skin without letting it breath could be an issue if the hydrogel is too wet (not enough cross-links)

Materials

• Sodium Alginate Hydrogel Polymer ($40)
• Phosphate Buffered Saline (PBS) ($51)
• Calcium Carbonate (to make cross links for hydrogels) ($40)
• Cuvettes ($28)
• Teflon Spacers (4 for each slide of standard height) ($20)
• Ibuprofen ($5)
• Binder clips ($5)
• Glass plates ($25)
• Syringe  ($50)
• Micropipette and tips ($300)
• Fabric ($10)
• Adhesive ($25)
• Mortar and Pestle
• Beaker
• Graduated cylinder (at least a GED)

General Summary of Procedure

Hydrogel creation

• Three different concentrations of Ca+ ions to create three different thicknesses of hydrogel

Concentration release testing on all three thicknesses

• UV Spectroscopy 

Tensile testing

• On three different Ca+ concentrations 

Standard Operating Procedure (SOP)

Created: 6-May-2014

Last Revised: 8-May-2014

Section 1 – Process

Sodium alginate is a polymer that comes in a powder form that can be weighed out and added into aqueous solution to make hydrogels. Cross-links between polymer chains are created with the addition of calcium carbonate to the aqueous alginate solution. As the calcium ions form cross-links with the sodium alginate, structure is added and the solution’s liquidity decreases so that it becomes a gelatin.

Section 2 – Hazardous Chemicals

Calcium Carbonate, Sodium Alginate

Section 3 – Potential Hazards

Sodium alginate and calcium carbonate should be handled with care. Proper lab attire should be worn including lab coat, goggles, and protective gloves. Hazards for sodium alginate and calcium carbonate include slight irritation after skin contact. Avoid ingestion and inhalation. Small spills of calcium carbonate can be cleaned with water and disposed of. Masks should be worn to avoid inhalation of calcium carbonate and sodium alginate. Refer to MSDS for more information.

Section 4 – Special Handling Procedures and Storage Requirements

Keep containers of sodium alginate and calcium carbonate tightly closed. Keep containers in a cool, well-ventilated area.  Due to water evaporation, store hydrogels in an airtight container.

Section 5 – Materials List

Sodium alginate, phosphate buffered saline (PBS), calcium carbonate, cuvettes, teflon spacers, ibuprofen, binder clips, glass plates, syringe, micropipette and tips, fabric, adhesive

Section 6 – Process Steps (Current work in Progress)

1. Prepare glass slides with teflon spacers in between, and hold together with binder clips to form a flat mold for the hydrogels
2. Prepare __ grams of sodium alginate and __ grams of ibuprofen in a ___ solution of distilled water
3. Vortex mixture into solution for __ minutes
4. Prepare a calcium carbonate solution of __ grams in a __mL solution of water.  Prepare and sterilize a __mL syringe.
5. With the syringe, take up __mL of sodium alginate solution and insert solution with syringe in the center of the hydrogel mold
6. Immerse the plates in the calcium carbonate solution for __ minutes