Chapter 8 - Final Report Draft

This week was dedicated to writing the first draft of our final report. The contents of the report include the sections from the given report template plus the following:

• Revised timeline and budget (with final prices)
• Detailed procedure
• Calibration curve and Math Models for Release

We are awaiting feedback on this report so we may proceed with making necessary changes for the final version of our report.

In addition to writing and submitting this report, we contacted Pedro to arrange a time that we can use the lab to produce a deliverable for our presentation.

We also made this banging graph:

Chapter 7 - Math Model

The rate of release is most likely dependent on three factors: time, the concentration of dye in the hydrogels, and the concentration of gel in solution. The results, as plotted below, suggest an exponential model which is dependent only on the concentration of dye in the hydrogel. Because the release approaches nearly 1, the concentration of dye in solution, if it has an effect, would manifest its effect toward the end of trial when the concentration gradient between the dye and the solution is greatest. These considerations suggest that the model described in the below MATLAB analysis is likely accurate. The coefficients in the exponential models, represented by the slopes of the regressions done in week 6, can be plotted against the concentrations of sodium alginate used to prepare the beads to form another regression that can be used to predict the release coefficient for other concentrations. This model could also then be used determine an appropriate concentration of alginate used to prepare beads for a desired release rate.

Flipping the axes allows prediction based on release rate. Because it is the same data, the Coefficients of Correlation and Determination will be the same.

More data points would increase not only the confidence bounds but also the domain for interpolation. Each trial takes over an hour of constant measurements however making it necessary to balance number of trials with domain and confidence.

Chapter 6 - MATLAB

In lab, we learned that it is common practice to represent the release as a percentage of the initial amount. The initial amount of mehtylene blue in each trial was (9mL)*(5.9mg/mL). The concentration in solution was divided by this value to determine the release as a percent.

When the data was processed into Matlab, releases exceeding 100% were observed. This is of course impossible. The mass in solution was greater than the initial mass by a small amount. This discrepancy can be explained by the error in the callibration curve. The y-intercept was greater than any of the errors in the trials. Because the y-intercept for the callibration curve should be 0, the y-intercept was excluded from subsequent calculations.

Plots:

Attempting to fit an exponential curve to each of these, the natural logarithm of the difference was taken: ln(1-release). Running a linear regression for each of these:

R² = 0.9843

R² = 0.9880

R² = 0.9914

The slopes and y-intercepts of these lines can be used to form an exponential curve to fit the time vs. release data. Additionally, these slopes can be compared with concentration of sodium alginate to find a relation between release rate and preparation of alginate.

Chapter 5, Part B - The Data

The data from the UV/vis was saved as an ascii file. It was then processed into both excel and MATLAB. First, the spectra for the dilutions of the stock solution were inspected and the highest absorbance for each was found. The wavelength 664 nm had the highest absorbance for the majority of trials and this wavelength was used in the calibration curve. The absorbance was plotted against the concentration.

The equation of the line was: Absorbance = 0.1968*Concentration-0.0102; Coefficient of Determination 0.999.

The spectra for the trial using 0.75% sodium alginate was processed next. Again the data was pulled into Excel and MATLAB. The calibration curve was used to interpolate the concentration of methylene blue in solution when the sample was drawn. Using this concentration with the volume of water(50mL), the mass of dye in the solution can be found. Because each trial used 9mL of sodium alginate solution at 5.9 mg/L, the initial mass of methylene blue in the beaker can be determined. Subtracting the mass of methylene blue in the solution from the initial mass in the hydrogels, the mass remaining in the hydrogels can be found. Because the volumes of each are known, the concentrations can also be found.

Chapter 5, Part A - The Experiment

This week, we met up over the weekend with our mentor, Pedro, to experiment with the goal of testing the effects of various concentrations of sodium alginate on the release rate of the drug. First, we created a stock solution of Methylene Blue (a blue dye) by mixing a known mass into a one liter volumetric flask. Then, we diluted the solution to create 7 total dye mixtures (5 initially, 2 additionally) with varying concentrations that would allow us to create a calibration curve. We ran each sample through the UV spectrometer and recorded the spectrum data. Once we had our molar absorption amounts, we could test the release rate of the alginate. We created three different concentrations of alginate solution and mixed them with a calcium chloride solution of a known concentration. We mixed the alginate in a solution with dye so we could measure the concentration of dye in the colorless calcium chloride solution as they dissolved. We created three solutions, and withdrew a sample from each one every six minutes for an hour. We then plotted this data to determine the release rates.

We prepared a range of concentrations (mg/L) of methylene blue with distilled water (left to right - greatest to least).

We mixed methylene blue with sodium alginate (after collecting absorbance data for the different concentrations of methylene blue with the UV/vis spectrophotometer).

It was necessary to heat up the mixture of methylene blue and sodium alginate to speed up the dissolving process.

These three beakers contained unique concentrations of sodium alginate with methylene blue (as seen, concentrations of sodium alginate used included 0.75 mg/L,1.00 mg/L, and 1.25 mg/L).

This is an overhead view of the beakers of methylene blue and sodium alginate.

Once the sodium alginate and methylene blue was thoroughly mixed, a pipette was used to transfer the solution to a beaker of calcium chloride in order to produce hydrogel beads.

The hydrogel beads were poured on to a mesh material.

The labels designating the concentration amount of sodium alginate used to make a set of hydrogel beads were transferred to their appropriate partner beakers of calcium chloride and hydrogel beads.

This is an overhead view of a beaker with calcium chloride and hydrogel beads.

Each of the beakers that contained unique concentrations of sodium chloride with methylene blue (this solution in the form of many hydrogel beads) with calcium chloride were tested in the UV spectrometer to determine the rate of dye being released.

Here's a picture of the group with our hydrogel beads!

Chapter 4 - Reactions

We met with Pedro again this week to discuss/consult with him about the procedure. The dye of choice was narrowed to tartrazine or potassium permanganate. Although a relation between the absorbance and time could be used to characterize the release rate, knowing the solution of the dye in water will also be valuable. To make this conversion, a stock solution of potassium permanganate will be created and solutions with varying concentrations will be produced from this. Their absorbances will be measured using a UV spectrometer to create a calibration curve for Beer's Law. We also set up another time with Pedro this upcoming weekend to meet to actually perform the experiment.

Chapter 3 - Practice

This week in lab, we prepared our first samples of hydrogels. First, we created a solution of sodium alginate by mixing it in water. Since no scales were available, the amount used was estimated in order to try to approximate a 1% solution. This solution was added to the calcium chloride to produce beads. The experiment was immediately successful, despite the fact that precise measurements and tools were not used. We acquired more familiarity with how to create hydrogels and will be able to use that knowledge to be able to perform the large amount of mixtures we will need to do when we perform our actual experiments with precise, varying concentrations.

This is a bead produced from mixing sodium alginate, calcium chloride, and tap water displayed at the tip of a pipette

Glen showed off the gel forming in the test tube.

The gel was removed from the test tube and placed in the cap.

Chapter 2 - Gathering Supplies

This week in lab, we explored hydrogels further and finalized some of our ideas. There was a demonstration that further showed how hydrogels were formed and helped provide a visual for what our group would experience. We also recieved the sodium alginate and pipettes we needed to continue our experiment. Because we are going to need lab space and lab equipment to perform the tests and design a delivery mechanism, we contacted a TA in the chemistry department, Pedro Amaral. We met with Pedro and discussed the possibility of using the labs and the feasibility of what we wanted to do.

Sodium Alginate

Pipettes... 100 for only $5.00!

Chapter 1 - Research and Project Proposal

This week in lab, we learned about what hydrogels were, methods of creating them, and how they are commonly used. The project was introduced, and we began brainstorming ideas for the project. Our current idea is to use hydrogels prepared using various methods to create a multi-stage oral drug delivery method designed to provide the drug at a constant rate to the person, despite the body's constant absorption of the drug. We also decided on what materials we would need to complete the experiment, and which ones we would need to order ourselves. We ordered sodium alginate and pipettes to perform the experiments, and contacted a member of the chemistry department to meet up about using the department's equipment. We plan to test the rate of delivery of the drug using a UV spectrometer, measuring the absorption when dye is used to represent the drug that would be delivered. The project proposal was also completed, giving us a better idea of how we plan to manage our time.