Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 2, Pages: 756-761  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link:  
Synthesis and Swelling Kinetic Study of BSA-based  
Hydrogel Composite by Subcritical Water  
Zahra M. Esfahan * , Shamsul Izhar * , Mohd Halim Shah Ismail , Hesam Kamyab , Yoshida  
Hiruyuki , Razif Harun  
Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, 43300 Serdang, Selangor, Malaysia  
Department of Engineering, Razak Faculty of Technology and Informatics, Universiti Teknologi Malaysia, 54100, Kuala Lumpur, Malaysia  
Received: 29/08/2019  
Accepted: 15/04/2020  
Published: 20/05/2020  
This study, for the first time, aimed to analyse ‘Bovine serum albumin’ hydrogel composite by simple and quick method (SCWT)  
since not only there had been some indications that the low temperature subcritical water treatment may be as valuable products as its  
high temperature treatment, but also, the positive outcome would put a stop to the waste of energy and money. For BSA-based hydrogel  
at first, the optimum conditions were identified by assessing the effect of different influential parameters (SCWT temperature, time).  
SCWT was done using a batch subcritical reactor. Additionally, the characterization tests were carried out on the BSA-based hydrogels  
which was produced by this unique method. BSA-based Hydrogel preparation condition by SCWT accurately was investigated and  
optimized SCWT condition according to maximum ESR (50%). Schott kinetic swelling model provided evidence to approve two-step  
water diffusion mechanism in BSA-based hydrogel by SCWT.  
Keywords: Bovine Serum Albumin, Subcritical Water, Batch Reactor, Hydrogel  
Introduction 1  
Biomaterials have been proven to be quiet beneficial to  
motivated researchers to investigate on replacing the time  
consuming, toxic methods by clean and safe SCW technology.  
According to the literature, it is assumed that BSA solution  
under Sub-CW treatment, has aggregation-decomposition-  
aggregation-decomposition pathway (15). In this case, this  
study assumes that BSA coagulates to BSA solid network  
(BSA-based hydrogel). So based on this, Sub-CW treatment  
of BSA can be a great, novel method for producing BSA-based  
hydrogel without using any chemicals and crosslinker in a very  
short time.  
Continuous efforts have been made to produce strong and  
biocompatible bovine serum albumin hydrogels with retained  
protein function; for example, the ability to bind, and release  
types of well-defined molecules (16, 17, 18, 19). The BSA-  
based hydrogels made by the thermal method have already been  
well established and have been working on the induction gel  
mechanism of proteins such as BSA (20, 21, 22). The main  
drawback of heat-inducing method is the broadly protein  
denaturation, with the risk of compromising protein  
functionality and biocompatibility (23). Moreover, besides the  
disadvantages of the denaturation problem, the time consumed  
by the incubation process is another drawback (24, 25).  
Electrostatically-triggered serum albumin hydrogels is another  
preparation method of albumin hydrogels introduced very  
recently (25). Despite the fact that this proposed method  
reduced the time consumption and solved the denaturation  
problem, still it is long and needs chemicals that are not  
human beings as they have a diverse range of applications in  
food, medicine, and many other areas (1, 2, 3). For instance, the  
vast range of proteins has been used as a good source of  
protein-based biomaterials (4). It is not surprising that the  
demand for natural and organic products has increased  
significantly worldwide as they are considered less harmful in  
comparison with non-organic products. Nowadays, there are  
numerous natural products in the market for cosmetics, food  
additives, and medicinal purposes (5). Many of the above-  
mentioned biomaterials are protein-based (6, 7). Protein-based  
hydrogels are the most common biopolymers shaped from  
proteins and have medical applications in the drug delivery  
system, tissue engineering, ect (8, 9). However, the quality and  
difficulty of each method varies significantly for different  
protein sources (10, 11, 12). Therefore, given the afore-  
mentioned importance of biomaterials for natural products,  
finding highly efficient isolation methods for protein-based  
biomaterials as well as understanding and identifying the  
applications and properties for each protein-based biomaterial  
is vitally important. Subcritical water technology is a novel  
method that recently take an attention of researchers to  
produced variable biomaterials such as bioplastic and biomass  
without using additive, catalyst or any toxic chemicals (13, 14).  
Additionally, promising properties of water in high temperature  
and pressure range (SCW) and coagulation of the protein  
structure under subcritical water treatment conditions  
Corresponding author: Shamsul Izhar, Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, 43300  
Serdang, Selangor, Malaysia. Email: and