A Simplified Approach to Evaluating Water Absorption Kinetics in Swellable Polymer Matrices
S. Y. Patil*, R. K. Jat
Department of Pharmacy, Department of Shri Jagdish Prasad Jhabarmal Tibrewala University,
Vidyanagari, Jhunjhunu, Rajasthan – 333010, India.
*Corresponding Author E-mail: subhashreg@gmail.com
ABSTRACT:
The purpose of this research was to find a better way to measure the rate of water absorption in swellable polymer matrices using a less complicated approach. When it comes to kinetic research, the current methods, such as optical microscopy, spatula techniques, and nuclear magnetic resonance imaging, can be quite labour-intensive and complicated. This problem was solved by introducing a technique that makes use of both perforated and non-perforated plastic sheets. On the 2 cm² sheets, black circles with different diameters were printed. On top of these circles, in a Petri dish filled with water, were inserted polymer compacts. The water absorption (W) was measured by removing and weighing the sheets and compacts at predetermined intervals. U, the average water penetration velocity, and Q, the mass degree of swelling, were computed from these values. This technique allowed for the front of the erosion to remain undisturbed while the water absorption kinetics were monitored continuously until the compacts were completely worn away. The results demonstrated that there was no notable distinction (p<0.05) in W, U, and Q between the perforated and non-perforated sheets. After an initial burst of rapid water uptake, swelling peaked at five hours, and then began to fall as a result of the gelled layer's polymer chain degradation. A potential alternative to traditional methods for investigating the kinetics of water absorption in polymer matrices, this approach is user-friendly, sensitive, and straightforward.
In the field of controlled drug delivery systems, water-swellable polymers have garnered significant attention for their ability to prolong drug release. Among these polymers, hydroxypropyl methylcellulose (HPMC) is extensively used in the formulation of extended-release matrix tablets. HPMC is known for its excellent compression properties and adequate swelling behavior, which facilitates the rapid formation of a gel layer around the matrix. This gel layer plays a crucial role in regulating the release of the drug, making HPMC a preferred choice for extended-release formulations.1-4 The release of drugs from such swellable matrices is primarily governed by diffusion through the gel layer, which progressively forms as the polymer matrix absorbs water. As the polymer chains hydrate and disentangle, they create a hydrated barrier that controls the drug's release rate. Therefore, understanding the water absorption kinetics of swellable polymers is essential for predicting and optimizing drug release profiles. However, accurate assessment of water absorption kinetics remains challenging due to limitations in existing methods. Several techniques, including polarized microscopy, photomicrography, optical imaging, the spatula method, and nuclear magnetic resonance imaging (NMR), have been employed to study water absorption in polymer matrices.5-8 While these methods offer valuable insights, they are often complex, time-consuming, and require specialized equipment. Additionally, certain methods may disturb the erosion front, leading to inaccurate results.9-12 These challenges necessitate the development of a more straightforward, reliable, and efficient technique to investigate water absorption kinetics.
To address these limitations, a novel method has been developed for the assessment of water absorption kinetics in swellable polymer matrices. This method utilizes perforated and non-perforated plastic sheets printed with black concentric circles of varying diameters. Polymer compacts are placed on the sheets and submerged in water within a Petri plate. At predetermined time intervals, the sheets and compacts are removed and weighed to determine the amount of water absorbed (W). From these measurements, key parameters such as the mass degree of swelling (Q) and the average velocity of the water penetration front (U) can be calculated.13-16
The developed method offers a comprehensive analysis of water absorption kinetics without disrupting the erosion front, ensuring accurate and reliable data. By eliminating the complexities of conventional techniques, this approach provides a practical and efficient solution for evaluating the swelling behavior of polymer matrices. The findings from this study contribute to a better understanding of the water absorption process, ultimately aiding in the design and optimization of controlled drug delivery systems.17-20
MATERIALS AND METHODS:
Water absorption kinetics:
Evaluation of the water-holding capacity of polymeric matrices was done by analysing their water absorption kinetics. This correlates with the drug release via the gel layer. We assessed the mass degree of swelling (Q), the velocity of the water penetration front (U), and the weight of the absorbed water (W). Placing each obtained compact on its own 2 cm2 plastic sheet, we used computer-aided software to design black concentric circles. The sheets may be either perforated or nonpeforated. For a 13 mm compact, the sketched concentric circles had dimensions of 13, 14, 16, 18, 20, 22, 24, 26 mm, and for an 8 mm compact, the diameters were 8, 9, 10, 12, 14, 16, 18, 20 mm. The containers set on each plastic sheet were immersed in a petri dish with 50 cc of water at a temperature of 37±20C in isolation. The water uptake was determined by removing the plastic sheet and compact from the petri dish at hourly intervals, blotting excess water with tissue paper, and then weighing the mixture. After 13 hours, the compacts' weight, thickness, and diameter were measured. The mass degree of swelling (Q), rate of water absorption, and average velocity of water penetration (U) were calculated using the data collected for weight of water absorbed. (Table-1).
RESULTS AND DISCUSSION:
Water absorption kinetics are mainly evaluated for evaluation of water holding capacity of polymeric matrices which was directly correlated with release of drug through gel layer formed around the matrices. We have determined the weight of water absorbed (W), the average velocity of water penetration front (U) and mass degree of swelling (Q) were calculated for Moringa coagulant (13 mm), Nirmali coagulant (10 mm) and Ash Gourd Coagulant (8 mm).
Figure 1: Pictures of swollen matrices of Moringa coagulant, Nirmali coagulant and Ash Gourd Coagulant.
Table 1: Weight of water absorbed in matrices*
|
Time |
|
Weight of water absorbed (g) |
|||
|
|
Moringa coagulant (8mm) |
Moringa coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
0.318±0.006 |
0.344±0.045 |
0.2836±0.001 |
0.2036±0.021 |
0.4166±0.054 |
|
2 |
0.4134±0.005 |
0.4243±0.0751 |
0.325±0.0413 |
0.2623±0.011 |
0.4463±0.0052 |
|
3 |
0.4063±0.0020 |
0.4346±0.0731 |
0.3532±0.0621 |
0.2156±0.021 |
0.4563±0.002 |
|
4 |
0.4256±0.0014 |
0.4456±0.0724 |
0.354±0.0225 |
0.2353±0.020 |
0.478±0.006 |
|
5 |
0.4468±0.0017 |
0.4849±0.0726 |
0.4763±0.0124 |
0.384±0.006 |
0.314±0.007 |
|
6 |
0.4773±0.0014 |
0.5523±0.0682 |
0.5068±0.0406 |
0.2633±0.005 |
0.5786±0.005 |
* Indicating Mean ± S.D. (n=3)
Table 2: Weight of water absorbed in matrices*
|
Time |
Weight of water absorbed (g) |
||||
|
|
Nirmali coagulant (8mm) |
Nirmali coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
0.435±0.004 |
0.546±0.051 |
0.2866±0.004 |
0.3136±0.021 |
0.4196±0.042 |
|
2 |
0.4678±0.006 |
0.5543±0.0343 |
0.3518±0.0223 |
0.3323±0.021 |
0.4353±0.005 |
|
3 |
0.4756±0.0021 |
0.5623±0.0523 |
0.3752±0.0189 |
0.3457±0.032 |
0.4543±0.004 |
|
4 |
0.4876±0.0016 |
0.5768±0.0414 |
0.3867±0.0342 |
0.3578±0.015 |
0.4789±0.003 |
|
5 |
0.4890±0.0018 |
0.5869±0.0261 |
0.3986±0.0241 |
0.3765±0.004 |
0.4898±0.007 |
|
6 |
0.4975±0.0013 |
0.5943±0.0122 |
0.4028±0.0216 |
0.3955±0.002 |
0.4981±0.005 |
Table 3: Weight of water absorbed in matrices*
|
Time |
Weight of water absorbed (g) |
||||
|
|
Ash Guard coagulant (8mm) |
Ash Guard coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
0.556±0.005 |
0.676±0.045 |
0.3186±0.002 |
0.3368±0.018 |
0.4256±0.021 |
|
2 |
0.5689±0.007 |
0.6834±0.0127 |
0.3428±0.0153 |
0.3436±0.019 |
0.4383±0.006 |
|
3 |
0.5791±0.0013 |
0.6965±0.0233 |
0.3532±0.0191 |
0.3567±0.031 |
0.4463±0.003 |
|
4 |
0.5867±0.0012 |
0.7012±0.0312 |
0.3673±0.0126 |
0.3654±0.017 |
0.4591±0.008 |
|
5 |
0.5916±0.0016 |
0.7145±0.0131 |
0.3734±0.0210 |
0.3785±0.005 |
0.4686±0.006 |
|
6 |
0.6034±0.0011 |
0.7254±0.0212 |
0.3866±0.0260 |
0.3851±0.003 |
0.4974±0.003 |
Figure 2: Plot of Water absorbed (gm) Versus Time (hours)
Ibuprofen matrices have shown highest water absorption while lacosamide shows lowest water absorption. There was significant difference observed in weight of water absorbed in diclofenac sodium and lacosamide matrices, ibuprofen and diclofenac sodium matrices, 8mm moringa coagulant and lacosamide matrices.
Table 4: Mass degree of swelling of matrices*
|
Time |
Mass degree of swelling (Q) |
||||
|
|
Moringa coagulant (8mm) |
Moringa coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
1.691±0.024 |
2.196±0.014 |
1.881±0.024 |
1.987±0.04 |
1.908±0.05 |
|
2 |
1.705±0.025 |
2.361±0.0211 |
1.917±0.012 |
2.109±0.05 |
1.968±0.06 |
|
3 |
1.792±0.022 |
2.389±0.0306 |
2.017±0.018 |
2.268±0.14 |
1.279±0.09 |
|
4 |
1.809±0.021 |
2.407±0.020 |
2.198±0.032 |
2.356±0.03 |
1.519±0.01 |
|
5 |
1.824±0.019 |
2.488±0.015 |
2.298±0.033 |
2.408±0.05 |
1.876±0.16 |
|
6 |
1.901±0.026 |
2.618±0.032 |
2.326±0.028 |
2.563±0.19 |
1.979±0.24 |
Table 5: Mass degree of swelling of matrices*
|
Time |
Mass degree of swelling (Q) |
||||
|
|
Nirmali coagulant (8mm) |
Nirmali coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
1.716±0.014 |
2.365±0.016 |
1.967±0.027 |
1.988±0.06 |
1.994±0.02 |
|
2 |
1.765±0.022 |
2.465±0.024 |
1.996±0.019 |
2.153±0.06 |
2.168±0.06 |
|
3 |
1.789±0.028 |
2.689±0.028 |
2.025±0.016 |
2.298±0.19 |
2.269±0.04 |
|
4 |
1.817±0.025 |
2.733±0.026 |
2.145±0.036 |
2.328±0.07 |
2.545±0.02 |
|
5 |
1.828±0.016 |
2.896±0.018 |
2.245±0.034 |
2.498±0.06 |
1.968±0.25 |
|
6 |
1.979±0.035 |
2.975±0.037 |
2.311±0.027 |
2.503±0.13 |
1.986±0.29 |
Table 6: Mass degree of swelling of matrices*
|
Time |
Mass degree of swelling (Q) |
||||
|
|
Ash Guard coagulant (8mm) |
Ash Guard coagulant (13mm) |
Diclofenac sodium |
Lacosamide |
Ibuprofen |
|
0 |
0 |
0 |
0 |
0 |
0 |
|
1 |
1.826±0.011 |
2.416±0.014 |
1.985±0.014 |
2.086±0.05 |
1.853±0.02 |
|
2 |
1.968±0.023 |
2.458±0.022 |
2.025±0.015 |
2.126±0.06 |
1.989±0.03 |
|
3 |
2.089±0.028 |
2.598±0.035 |
2.156±0.019 |
2.245±0.23 |
2.109±0.02 |
|
4 |
2.178±0.025 |
2.756±0.016 |
2.265±0.022 |
2.312±0.04 |
2.593±0.05 |
|
5 |
2.786±0.016 |
2.898±0.012 |
2.368±0.038 |
2.463±0.08 |
2.876±0.17 |
|
6 |
2.981±0.033 |
2.906±0.025 |
2.408±0.072 |
2.583±0.32 |
2.968±0.05 |
* Indicating Mean±S.D. (n=3)
Figure 3: Plot of Mass degree of swelling (gm) Vs Time (hours)
Mass degree of swelling is depending on amount of water absorbed both are correlated with each other. Similar to rate of water absorption mass degree of swelling was found to be highest at 8th hour. 13mm tablet of moringa coagulant shows highest mass degree of swelling at 8th hour. Significant difference was for mass degree of swelling in between 8mm and13 mm matrices of the moringa coagulant, lacosamide and ibuprofen matrices, ibuprofen and diclofenac sodium matrices, 8mm moringa coagulant matrices and diclofenac sodium matrices, 13mm moringa coagulant matrices and ibuprofen matrices (P < 0.05). So, our results were more productive as compare to previous research.
Compared to previous research, the present method proved to be more efficient and reliable for evaluating water absorption kinetics and swelling behavior. The study's non-destructive approach ensured the preservation of the polymer network, allowing for accurate, reproducible measurements. These findings provide substantial evidence for the potential application of natural coagulants in the development of controlled drug delivery systems, offering a promising alternative to synthetic polymers.
CONCLUSION:
The present method for studying water absorption in swellable polymer matrices has demonstrated significant advantages over conventional optical methods. Unlike destructive techniques, this approach ensures the integrity of the polymer matrix throughout the study, allowing continuous observation of water absorption kinetics. One of its key strengths is its simplicity and non-destructive nature, eliminating the need for complex instrumentation or sophisticated analytical tools.
The evaluation of water absorption kinetics and mass degree of swelling in polymeric matrices, particularly using natural coagulants such as Moringa, Nirmali, and Ash Gourd, provided valuable insights into their water-holding capacities. This study established a direct correlation between the amount of water absorbed and the degree of swelling, which further influenced the drug release behavior through the gel layer formed around the matrices.
The results demonstrated that Ibuprofen matrices exhibited the highest water absorption, while Lacosamide matrices showed the lowest. Notable differences in water absorption were observed between Diclofenac sodium and Lacosamide matrices, as well as between Ibuprofen and Diclofenac sodium matrices. The findings also highlighted a significant distinction in water absorption between Moringa coagulant matrices of 8 mm and 13 mm sizes, with the larger matrices displaying higher water absorption.
The mass degree of swelling followed a similar trend, with the highest values observed at the 8th hour of the experiment. Moringa coagulant matrices of 13 mm exhibited the most significant swelling compared to the other matrices. Significant differences in swelling behavior were evident among the various formulations, particularly between 8 mm and 13 mm Moringa coagulant matrices, Lacosamide and Ibuprofen matrices, and Ibuprofen and Diclofenac sodium matrices. The variations in swelling were statistically significant (P < 0.05), further supporting the robustness of the findings. Moreover, the method is notably less labor-intensive and more cost-effective compared to traditional approaches. It requires only a single sample for a comprehensive evaluation, reducing material consumption and experimental time. This makes it particularly advantageous for routine analysis and large-scale studies. Additionally, the absence of intricate setups and extensive sample preparation further enhances its practicality, making it accessible to researchers across various settings. A distinguishing feature of this method is its ability to provide complete water absorption kinetics without disrupting the polymer's loosely bonded network. This characteristic allows for an accurate assessment of the polymer’s swelling behavior, which is essential for understanding drug release mechanisms in controlled-release formulations. The reliability and reproducibility of the results further establish the credibility of this method, positioning it as a promising alternative for evaluating water absorption in swellable polymer matrices.
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Received on 18.03.2025 Revised on 20.03.2025 Accepted on 11.04.2025 Published on 14.04.2025 Available online from April 18, 2025 Asian J. Research Chem.2025; 18(2):109-113. DOI: 10.52711/0974-4150.2025.00018 ©A and V Publications All Right Reserved
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