Permeability Properties I: Artificial Membranes

Aquino, Arquero, Galut, Villaroman, CJ B.

Natural and Applied Sciences Department

College of Arts and Sciences

Nueva Ecija University of Science and Technology

ABSTRACT

The laboratory activity explores the permeability properties of gelatin membranes and their potential
applications. Gelatin is a popular material for making artificial membranes due to its biocompatibility and
ease of preparation. Recent research has shown progress in the development of artificial membranes for
various applications such as water desalination and protein purification. By investigating the permeability
properties of gelatin membranes using a diffusion-based method, this laboratory activity aims to provide a
deeper understanding of the factors influencing the transport of molecules across a membrane. This study
aims to help researchers determine the equilibrium concentrations for chloride ions across a selectively
permeable membrane and explain how the nature of solutes affects the differences in chloride equilibrium
concentrations. A 5% gelatin solution is prepared by dissolving 1 g of gelatin powder in 100 mL of water
and boiling it for 5 minutes. Two solutions are then made - Solution A (0.20 g NaCl in 50 mL water) and
Solution B (0.20 g NaCl in 50 mL gelatin solution). A Longganisa skin is used as a membrane material to
create a diffusion bag filled with Solution B, which is immersed in a solution for 30 minutes. The diffusion
rates of NaCl are measured by comparing the color changes of Solution A and Solution B. The diffusion of
NaCl from Solution B into Solution A through the gelatin membrane in the diffusion bag can be determined
by comparing the initial and final concentrations of NaCl in the gelatin solution. The rate of diffusion is
influenced by factors such as concentration gradient, molecule size, temperature, and solvent density. The
presence of NaCl can be identified using silver nitrate, which reacts with halide ions to form insoluble silver
halides. The endpoint of the reaction is detected using potassium chromate, which forms a reddish-brown
precipitate of silver chromate when excess silver ions are present. The experiment showed that diffusion
occurred from high to low concentration, with factors such as concentration gradient, molecule mass,
temperature, and solvent density impacting the rate of diffusion. NaCl presence was confirmed with silver
nitrate and potassium chromate. The experiment enhanced understanding of artificial membrane
permeability and solute diffusion measurement.
INTRODUCTION glucose. The study found that the permeability of
gelatin membranes decreased with increasing
The Permeability Properties of Artificial crosslinking density, indicating that the
Membranes laboratory activity is a valuable tool crosslinking density is a critical factor in
for understanding the principles of membrane determining the permeability properties of gelatin
permeability and its applications. The activity membranes. Karthikeyan et al. (2019)
involves the use of an artificial membrane made investigated the permeability properties of gelatin
of gelatin to observe the diffusion of small membranes using a diffusion-based method. The
molecules such as NaCl. The permeability authors prepared gelatin membranes with
properties of an artificial membrane made from different concentrations of glutaraldehyde as a
gelatin, a biopolymer commonly used in crosslinking agent and measured their
membrane fabrication due to its biocompatibility permeability to various molecules, such as
and ease of preparation. The activity will involve glucose and fructose. The study found that the
preparing a 5% gelatin solution, boiling the permeability of gelatin membranes decreased
solution to ensure complete dissolution of the with increasing glutaraldehyde concentration,
gelatin powder, and fabricating a water-tight indicating that the crosslinking density is a crucial
diffusion bag using Longganisa skin. factor in determining the permeability properties
Researchers investigate the permeability of the of gelatin membranes. According to Peng et al.
gelatin membrane by comparing the diffusion (2020) the permeability properties of gelatin
rates of sodium chloride in Solution A and membranes using an osmosis-based method.
Solution B, which contains both sodium chloride They prepared gelatin membranes with different
and the gelatin membrane. surface modifications, such as the incorporation
of chitosan and graphene oxide, and measured
The study of membrane permeability properties is their permeability to various molecules, such as
an essential aspect of biological, chemical, and urea and creatinine. The study found that the
physical sciences. It determines the rate of flow surface modifications of gelatin membranes
of various molecules across it, and it is influenced significantly influenced their permeability
by the chemical and physical properties of the properties, indicating that the surface chemistry is
membrane. The permeability properties of a critical factor in determining the permeability
artificial membranes have gained significant properties of gelatin membranes.
attention in recent times due to their use in
various applications, such as drug delivery, water
filtration, and bioseparations. Gelatin is a popular
material for making artificial membranes due to its Recent research has shown significant progress
biocompatibility, low cost, and ease of in the development of artificial membranes and
preparation. The permeability properties of their potential applications in various fields. Also
gelatin membranes can be controlled by adjusting a study by Chen et al. (2021), they developed a
their composition, crosslinking density, and novel type of artificial membrane made of
surface chemistry. Several studies have cellulose nanofibrils that showed high selectivity
investigated the permeability properties of gelatin and permeability for water molecules. The
membranes using different techniques, such as authors demonstrated the potential applications
dialysis, diffusion, and osmosis. of this membrane in water desalination and
purification. In addition Kang et al. (2020) focused
Hong et al. (2019) investigated the permeability on the use of artificial membranes in the
properties of gelatin membranes using a dialysis separation of proteins. The authors developed a
method. The authors prepared gelatin membrane with pore sizes that can selectively
membranes with different crosslinking densities separate proteins based on their size and charge,
and measured their permeability to various demonstrating its potential in protein purification
molecules, such as bovine serum albumin and and analysis. The use of gelatin as an artificial
membrane in this laboratory activity is significant glass, analytical balance, distilled water, stirring
because it is a common biomaterial that can be rod, potassium chromate, silver nitrate,
easily manipulated to create different types of graduated cylinder, pipette, test tube, and
membranes. Gelatin has been used in various analog hot plates that used in this experiment
biomedical applications, including drug delivery, are from the laboratory of Nueva Ecija University
tissue engineering, and wound healing (Das et of Science and Technology, College of Arts and
al., 2019). The experiment demonstrates the Sciences Department.
potential applications of gelatin-based
membranes in controlling the diffusion of small The laboratory activity involves a series
molecules, which can be applied in various fields of steps to investigate the permeability properties
such as drug delivery and environmental science. of an artificial membrane made from gelatin. The
first step is to prepare a 5% gelatin solution by
Understanding the permeability properties of dissolving 1 g of gelatin powder in 100 mL of
gelatin membranes is crucial to developing water and boiling the solution for 5 minutes while
effective membranes for various applications. By stirring. This ensures that the gelatin is
investigating the permeability properties of completely dissolved and the solution is
gelatin membranes using a diffusion-based homogeneous. Next, two solutions are prepared
method, this laboratory activity aims to provide a - Solution A and Solution B. Solution A contains
deeper understanding of the factors influencing 0.20 g of NaCl dissolved in 50 mL of distilled
the transport of molecules across a membrane. water, while Solution B contains 0.20 g of NaCl
Moreover, this laboratory activity provides hands- dissolved in 50 mL of the gelatin solution. The
on experience in laboratory techniques such as purpose of preparing these solutions is to
solution preparation, membrane fabrication, and compare the diffusion rates of NaCl in the
measurement of permeability. These skills are presence and absence of the gelatin membrane.
essential for students in science-related To create the diffusion bag, Longganisa skin is
disciplines to develop a solid foundation for future used as the membrane material due to its ability
research and professional practice. This study to prevent leaks and ensure a tight seal. The bag
aims to help the researchers to determine the is filled with Solution B and immersed in a solution
equilibrium concentrations for chloride ions for 30 minutes. The ends of the bag are left untied
across a selectively permeable membrane. And and not immersed to prevent fluid entry. After the
explain how the nature of solutes dissolved in immersion period, the contents of the diffusion
each of the two solutions affect differences in bag are emptied into a clean beaker. To measure
chloride equilibrium concentrations. Furthermore the diffusion rates of NaCl, 0.5 mL of Solution A
the gelatin solution will act as a barrier and is pipetted into a clean test tube, and 50 µL of
prevent the diffusion of NaCl, as demonstrated by potassium chromate is added. Then, 50 µL
the absence of a brown color formation in portions of 2.9% silver nitrate are added until the
Solution BB, while a brown color will form in bright yellow solution changes to a permanent
Solution A due to the diffusion of NaCl. brown hue. This step is repeated for Solution B,
which contains the gelatin membrane. By
comparing the color changes of the two solutions,
we can determine the relative diffusion rates of
NaCl in the presence and absence of the gelatin
membrane. This laboratory activity provides a
practical and hands-on approach to
understanding the principles of membrane
METHODS
permeability and its applications in various fields.
The gelatin, salt, and longganisa skin
are from Aliaga, Nueva Ecija. Beaker, watch RESULTS & DISCUSSION
 is governed by several factors that impact the
speed at which a substance will move from an
area of high concentration to one of lower
concentration. Among the key factors that
influence the rate of diffusion is the concentration
gradient, which dictates the extent of the
concentration difference between the two
regions. A larger difference in concentration leads
to faster diffusion, while a smaller difference
results in a slower rate of diffusion as equilibrium
is approached. Additionally, the mass of the
diffusing molecules plays a critical role in
determining the rate of diffusion, with larger
molecules moving more slowly due to the
increased resistance they face while moving
through the substance. The temperature is
another crucial factor that affects the rate of
diffusion, with higher temperatures resulting in
greater molecular motion and energy, leading to
faster diffusion. Lastly, the density of the solvent
is another factor that can affect the rate of
diffusion, with higher solvent density slowing
down the rate of diffusion due to the greater
Figure 1. Water-tight diffusion bag using resistance the diffusing molecules face while
Longganisa skin filled with gelatin solution. passing through the denser medium.
By comparing the initial and final
After half an hour of immersion, Sodium concentrations of NaCl in the gelatin solution, the
chloride (NaCl) from Solution B diffused into the extent of NaCl diffusion can be determined. The
gelatin solution (Solution A) inside the diffusion presence of NaCl can be determined using silver
bag due to the concentration gradient. Diffusion nitrate as a reagent. In analytical chemistry, silver
refers to the movement of molecules from a high nitrate is used to identify the presence of halide
concentration area to a low concentration area, it ions, such as chloride, bromide, and iodide. Silver
will proceed until the concentration gradient is nitrate reacts with halide ions to form insoluble
eliminated, resulting in an equal concentration of silver halides which are easily identifiable by their
molecules on both sides of the membrane, or characteristic color and precipitation. For
equilibrium where the mobility of molecules does example, the addition of silver nitrate to a solution
not cease (Soult, 2021). By preparing two containing chloride ions results in the formation of
independent solutions, Solution A and Solution B a white precipitate of silver chloride. The endpoint
having different concentrations of NaCl, a of the reaction is detected using potassium
concentration gradient was generated which is chromate (K2CrO4), which reacts with the excess
the measurement of how the concentration of silver ions (Ag+) to form a reddish-brown
something varies from one location to another precipitate of silver chromate (Ag2CrO4). The
(Biology Online, 2022). point at which the red color appears and does not
The concentration of NaCl in the gelatin disappear with stirring indicates the endpoint of
solution inside the bag will increase as more NaCl the titration, which means that all of the chloride
molecules diffuse across the bag, and the ions have reacted with the silver nitrate (Science
concentration gradient gradually decreases. Ready, n.d.).
According to Molnar (2015), the rate of diffusion
 density on the permeability of gelatin
CONCLUSION membrane for bovine serum albumin
In conclusion, the experiment and glucose. Journal of Industrial and
demonstrated that diffusion occurred from Engineering Chemistry, 75, 22-26.
Solution B, which had a higher concentration of https://doi.org/10.1016/j.jiec.2019.01.01
NaCl, into Solution A, the gelatin solution, due to 5
the concentration gradient. The concentration Kang, J. W., Kim, H. N., Park, J. H.,
gradient decreased as more NaCl molecules Lee, M. C., & Cho, D. W. (2020). Protein
diffused across the bag. The rate of diffusion was separation using polymeric membranes
impacted by various factors such as the extent of with controllable pore sizes. Journal of
the concentration gradient, the mass of the Industrial and Engineering Chemistry,
molecules diffusing, the temperature, and the 86, 249-254.
density of the solvent. The presence of NaCl was https://doi.org/10.1016/j.jiec.2020.07.02
confirmed by using silver nitrate as a reagent and 4
potassium chromate as an indicator to determine Karthikeyan, K., Rao, R. M., & Uppaluri,
the endpoint of the reaction. Overall, the R. (2019). Study on the permeability of
experiment provided a better understanding of gelatin membranes with varying
the permeability properties of artificial glutaraldehyde concentrations. Journal
membranes and how to measure the diffusion of of Applied Polymer Science, 136(30),
solutes across these membranes. 47731.
https://doi.org/10.1002/app.47731
Molnar, C. (2015). 3.5 Passive
Transport. Pressbooks.
https://opentextbc.ca/biology/chapter/3-
REFERENCES
5-passive-transport/
Biology Online. (2022). Concentration
Peng, Y., Wang, W., Jiang, Y., Zhang,
gradient - Definition and Examples |
W., Li, X., & Deng, Y. (2020). Surface
Biology Online. Biology Articles,
modification of gelatin membrane by
Tutorials & Dictionary Online.
graphene oxide and chitosan for
https://www.biologyonline.com/dictionar
hemodialysis. Journal of Materials
y/concentration-gradient
Science: Materials in Medicine, 31(3),
Chen, S., Ma, S., Ma, Y., & Zhou, Q.
25. https://doi.org/10.1007/s10856-020-
(2021). Cellulose nanofibril membranes
06313-y
with high selectivity and permeability for
Science Ready. (n.d.). Mohr’s and
water purification. Carbohydrate
Volhard’s Method of Precipitation
Polymers, 257, 117626.
Titration – HSC Chemistry. Retrieved
https://doi.org/10.1016/j.carbpol.2020.11
from
7626
https://scienceready.com.au/pages/preci
Das, S., Pati, F., Choi, Y. J., & Rijal, G.
pitation-titration
(2019). A review on fabrication of
Soult, A. (2021). 8.4: Osmosis and
gelatin-based hydrogels for biomedical
Diffusion. Chemistry LibreTexts.
applications. Critical Reviews in Food
https://chem.libretexts.org/Bookshelves/I
Science and Nutrition, 59(1), 89-107.
ntroductory_Chemistry/Book%3A_Chem
https://doi.org/10.1080/10408398.2017.
istry_for_Allied_Health_(Soult)/08%3A_
1354975
Properties_of_Solutions/8.04%3A_Osm
Hong, K. H., Park, J. L., Song, K. D., &
osis_and_Diffusion
Lee, H. (2019). Effect of crosslinking
APPENDIX