1. Temperature Dependent Phase Characterization of κ-Carrageenan and Type B Gelatin
1Ryan Jones, 2Tyler Erickson, and 2Bratoljub H. Milosavljevic
Departments of 1Chemical Engineering and 2Chemistry, The Pennsylvania State University, University Park, PA 16802
MATERIALS AND METHODS RESULTS AND DISCUSSION
INTRODUCTION
ABSTRACT
ACKNOWLEDGEMENTS/REFERENCES
CONCLUSIONS
The first step of the experiment was creating the gel mixture. This
was done by first dissolving approximately 154.1 mg of both Kappa-
Carrageenan and B-type Gelatin in 10 mL of 0.2 M NaCl. The
concentration of NaCl was determined in order to observe three phase
changes identified in the introduction, which are also shown in the
phase diagram (Figure 1). A small amount of Ru(bpy)3
2+ was added to
the mixture, which was then heated at 85°C and stirred for ten minutes.
After the gel was mixed, it was then cooled and stored for the next part
of the experiment.
The next step of the experiment that was performed after the gel
was made was the time resolved laser photolysis study of the gel
mixture quenching by Ru(bpy)3
2+ (Figure 3). This was done by putting
the gel into a cuvette and then setting the cuvette in a water bath, which
controlled the temperature of the gel mixture. The water bath was then
placed in front of an SRS NL100 laser that emitted a 337.1 nm pulse.
A Tektronix TDS 2022B oscilloscope was used to obtain the
fluorescence intensity of the sample at temperatures 10°C, 23.5°C,
30°C, 37.5°C, 50°C and 60°C. The intensities were then used to create
an Arrhenius plot (Figure 5). The experimental setup can be seen in
figure 4.
After this step, the emission spectra of the gel mixture at the
various temperatures were obtained (Figure 4). This was done by
placing the gel mixture into a cuvette, which was then placed in a
Fluorolog fluorimeter. The gel mixture was then excited with a 450 nm
wavelength of light, and the emission spectra were measured at
temperatures of 10°C, 23.5°C, 30°C, 37.5°C, 50°C and 60°C. After the
spectra for each temperature was obtained, the plot of the maximum
wavelength versus the inverse time was plotted (Figure 6)
We would like to thank Dr. Bratoljub H. Milosavljevic and Kyle Munson for their
guidance and assistance during the experiment.
1Cao, Y., L. Wang, K. Zhang, Y. Fang, K. Nishinari, and GO. Phillips. "Mapping
the Complex Phase Behaviors of Aqueous Mixtures of κ-Carrageenan and Type B
Gelatin." The Journal of Physical Chemistry. B. U.S. National Library of Medicine, n.d.
Web. 05 Dec. 2016.
• At 0.2M sodium chloride,
• The Arrhenius plot shows that Ru(bpy)3
2+ decays more quickly within the gel
mixture with an increase in temperature.
• The plot of the maximum wavelength as a function of temperature shows
uniformity within the same phase, but a slight increase in maximum emission
wavelength (i.e. a slight decrease in energy emission) with increasing
temperature (through two successive phase changes.
In this experiment we utilized the Ru(bpy)3
2+ luminescence probe to
more fully characterize a gel mixture composed of 50% Kappa-
Carrageenan and 50% B-type Gelatin at various phases at a fixed salt
concentration of 0.2M. We obtained emission spectra and fluorescence
decay spectra to observe how the maximum emission wavelength and
quenching rate constant of the gel mixture changed while going through
three specific phases of the gel (Figure 1)1, ultimately providing
characteristic information about the microenvironment of this gel
mixture as a function of temperature.
The microenvironment of gels has always been difficult to
characterize due to its high viscosity and heterogeneity. In this
experiment, we attempted to characterize the microenvironment of a gel
composed of 50% Kappa-Carrageenan and 50% B-type Gelatin using the
luminescence probe Ru(bpy)3
2+ (Figure 2). Characterizing this gel
mixture is of great interest, since biopolymer mixtures like this gel are
used in the various chemical industries such as the food, cosmetic and
pharmaceutical industries. For these specific gels, Kappa-Carrageenan is
used to influence the stiffness of the overall gel mixture, while B-type
gelatin is used mainly for coating cell culture plates1. The luminescence
probe Ru(bpy)3
2+ was used during this experiment, since the
luminescence properties of this probe have been vigorously studied in
numerous experiments. This probe, whose mechanism of action is based
off confinement sensitivity, will be used in the experiment to determine
the quenching rate of the gel mixture while the mixture transitions
through its phases and to observe how the emission wavelength of the gel
mixture varies at different phases. The phases that we used during this
experiment were the phase containing the coexistence of HBIAPS phase
and the SPS phase, the HBIAPS phase, and the compatible phase.
Figure 1. Phase diagram of 1:1 Kappa-Carrageenan B-type Gelatin Mixture
(red line indicating salt concentration of interest)
Figure 2. Structure of the cationic luminescence probe Ru(bpy)3
2+
Figure 3. Time resolved photolysis experimental setup for measuring the decay of the
Ru(bpy)3
2+ probe
Figure 4. Fluorimeter experimental setup for obtaining the emission spectra of the gel mixture
with each probe
Figure 5. Arrhenius plot depicting the natural log of the gel mixture’s fluorescence
intensity as a function of inverse temperature
Figure 6. Plot of the gel mixture’s maximum emission wavelength as a function of temperature
From these plots, it is evident that the quenching rate constant of Ru(bpy)3
2+
significantly increases as temperature increases. Additionally, the maximum emission
wavelength for this gel mixture is constant within the same phase, but changes nearly
instantaneously during a phase change resulting in inflections about 300K and 315K.