**Abstract**

The conversion of biomass waste products to valuable products like cellulose hydrogel films is important in cell regeneration. In this study, the various biomass wastes: thanaka heartwood (TH), sugarcane bagasse (SB) and rice straw (RS) were used as cellulose resources. They were chemically treated using acid and alkali to obtain cellulose fibers. The yield percent of cellulose fibers depends on the nature of biomass materials. Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses showed that the amount of lignin and hemicellulose from these samples were successfully reduced by chemical treatment. Cellulose fibers were treated using the dimethylacetamide/ lithium chloride (DMAc/LiCl) system to obtain cellulose hydrogel solutions. Following this, the cellulose hydrogel films were prepared employing the phase inversion method without cross-linker. These films were transparent and flexible. In the present study, water retainable property and viscoelasticity of cellulose hydrogel films were measured. Antimicrobial activity tests of cellulose solutions have been carried out to be utilized to hydrogel films for biomedical application.

**Keywords:** cellulose hydrogel films, phase inversion method, biomass waste, antimicrobial activities

### **1. Introduction**

Hydrogels are three-dimensional polymeric networks kept together by crosslinked covalent bonds as well as weak cohesive forces such as hydrogen or ionic bonds [1]. Hydrogels consisting of hydrophilic polymer networks can absorb up to thousands of times their dry weight in water. Natural and synthetic polymerbased hydrogels are the two types of hydrogels, classed based on polymer source. Synthetic polymer-based hydrogels are fabricated from poly ethylene glycol, poly acrylic acid, polyacrylamide, poly vinyl alcohol etc. [2–5]. Natural polymer-based hydrogels are derived from various natural polymers, such as cellulose, gelatin, peptides, chitosan and alginate, etc. [6–8] and can be employed as advanced materials for tissue and organ repair and regeneration [9–11].

Commonly, all plant biomass consists of cellulose, hemicellulose, lignin, pectin and protein with cellulose being the major component making up to 33% of plant biomass. Use of cellulose has several advantages including biocompatibility, biodegradability, renewability, good mechanical strength, being environmentally friendly, and one of the safest materials on the earth [12]. Consisting of a linear chain of *β* (1→4) linked *D*-glucose units, it has properties of tasteless, odorless, insolubility in water and most organic solvents - a characteristic owing to its hydrogen bonds and Van der Waals forces that make it difficult for the dissolution [13].

Abundant in hydrophilic functional groups, including hydroxyl, carboxyl, and aldehyde groups, cellulose and its derivatives are ideal materials to prepare hydrogels films. Biodegradability, biocompatibility, non-toxicity, hydrophilicity, and tissue-mimicking characteristics of cellulose-based hydrogels make them useful in a variety of sectors, including food, agriculture, environmental remediation and medicinal applications, such as drug delivery [14, 15], tissue engineering [16–19], wound dressing [20–22], bio imaging [23–25] and wearable epidermal sensors etc. [26, 27]. The possibility of these numerous biomedical applications draws researchers into exploring renewable plant biomass-based cellulose alternatives to create hydrogel films [28–31].

Myanmar is an agricultural country with paddy crop production being the main agricultural production of the country. After being harvested; rice straw is generated in the field. Sugarcane bagasse is also fibrous by-product remaining after sugar extraction from sugarcane. And, these biomass wastes are always in abundance in many areas. The bark of thanaka is used for the production of cosmetic products such as thanaka powder, liquid, and paste [32]. The heartwood is often unused and becomes waste after the bark has been used up. As a result, as sustainable cellulose, thanaka heartwood, sugarcane bagasse and rice straw are biomass wastes that can potentially be converted into a valuable product like hydrogel films and they will become cost-effective items and can reduce environmental pollution. For this purpose, this study was carried out to convert cellulose solutions from these resources by using DMAc/LiCl systems to prepare cellulose hydrogel films. This research article has also reviewed the comparative study on the properties and nature of cellulosic hydrogels from various plant biomass wastes for biomedical applications.

### **2. Materials and methods**

#### **2.1 Materials**

Thanaka samples were obtained from Pakokku, Pakokku Township, Magway Region, Myanmar. Rice straw samples were obtained from Helgu Township, Yangon Region, Myanmar and Sugarcane bagasse collected from Nawaday Sugar Mill, Pyay Township, Bago Region, Myanmar.

#### **2.2 Preparation of treated fiber**

First, the collected raw materials were cut, washed and dried at 40°C. For the preparation of acid-treated samples, 10 g of raw samples were immersed in 500 mL, 4 vol% H2SO4 solution and stirred at 90°C for 2 h. After cooling down, the samples were washed, filtrated and collected as acid-treated samples. Similarly, they were again immersed in 500 mL, 10 vol % NaOH solution and stirred at 90°C. They were washed, filtrated and collected as base-treated samples. Again, they were immersed in 200 mL, 10 vol % NaOCl and stirred for the color bleaching. Then, cellulose fiber was obtained and dried at 50°C [29–31]. Percent cellulose fibers were found to be 28.50% of TH, 20.31% of SB and 21.63% of RS. Among them, the highest yield percent of cellulose was obtained from thanaka heartwood samples due to the hard portion (stem) of the plant. The yield percent of cellulose depends on the nature of plant materials.

*Comparative Study of Cellulose Hydrogel Films Prepared from Various Biomass Wastes DOI: http://dx.doi.org/10.5772/intechopen.99215*

### **2.3 Preparation of cellulose solution**

100 mL of deionized water was added into 1 g of cellulose fiber and stirred at room temperature overnight. They are then filtered and washed with ethanol. After that, 100 mL of ethanol was added to the swollen fibers and the mixture was stirred for 24 h. Then, ethanol was removed and added to 50 mL of DMAc and stirred overnight. Finally, 8 wt % of LiCl and DMAc were added to the swollen cellulose fibers and the solvent system adjusted to obtain a 1% concentration of cellulose solution. The mixture was stirred at room temperature to get the hydrogel solution.

### **2.4 Preparation of cellulose hydrogel films**

For hydrogel film preparation, 10 g of cellulose solution was poured into a Petri dish (10 cm diameter) and kept in a container filled with ethanol for 24 h. After this, transparent hydrogel films were obtained. Then, these films were washed with distilled water several times and immersed in distilled water and kept at room temperature. **Figures 1**–**3** illustrated the raw samples to cellulose hydrogel films for thanaka heartwood, sugarcane bagasse and rice straw, respectively. It was found that all cellulose hydrogel films were transparent and flexible but a little difference in their strength.

#### **2.5 Characterization techniques**

The structural changes of samples were analyzed by FTIR 8400 Shimadzu spectrophotometer by using the KBr pellet method in the MIR radiation with the wavelength from 4000 cm−1 to 400 cm−1 range with a resolution of 4.0 cm−1. The surface morphology of the samples was investigated by SEM (JEOL 15 kV). The X-ray diffraction (XRD) patterns of raw sample and pretreated cellulose fibers were recorded with CuKα radiation at 40 kV and 30 mA in the range of 2θ = 10°-40° by X-ray diffractometer (Smart Lab, Rigaku, Japan). The samples were dried in vacuum at room temperature before measuring them. The crystallinity index (CI) was calculated using the equation: CI (%) = (I002–Iam)/I002) × 100, where I002 is the maximum intensity of the peak (002) lattice diffraction and Iam is the intensity of diffraction attributed to amorphous cellulose [33]. Viscoelasticity of the hydrogel film, 2 cm in diameter with 5 mm in thickness, was determined by Auto Paar-Rheoplus equipment (Anton Paar Japan, Tokyo) in wet conditions at 37°C.

#### **2.6 Study on antimicrobial activity**

The study on antimicrobial activity of DMAc, DMAc/LiCl and cellulose solutions was performed by the agar well diffusion method [34]. Nutrients agar was

#### **Figure 1.**

*Photos showing (a) thanaka heartwood (b) acid-treated sample (c) base-treated sample (d) cellulose fiber and (e) thanaka heartwood cellulose hydrogel film (THCF).*

**Figure 2.**

*Photos showing (a) sugarcane bagasse (b) acid-treated sample (c) base-treated sample (d) cellulose fiber and (e) sugarcane bagasse cellulose hydrogel film (SBCF).*

**Figure 3.**

*Photos showing (a) rice straw (b) acid-treated sample (c) base-treated sample (d) cellulose fiber and (e) rice straw cellulose hydrogel film (RSCF).*

prepared according to Cruickshank's methods [35]. Firstly, nutrient agar (medium) was boiled and 20–30 mL of the medium poured into test tubes which were plugged with cotton wool. Secondly, the test tubes with the medium were autoclaved at 121°C for 15 minutes and they were cooled down to 30–35°C. Finally, the medium was poured into the sterilized petri dishes and 0.1–0.2 mL of test organisms were added into the dishes. In this study, the tested microorganisms are *Bacillus subtilis*, *Staphylococcus aureus*, *Pseudomonas aeruginosa*, *Candida albicans* and *Escherichia coli*. The agar was allowed to set for 2–3 hours. Fourthly, 10 mm agar-well was made with the help of a sterilized agar-well cutter. Finally, about 0.2 mL of samples were introduced into the agar-well and incubated at 37°C for 24 to 36 hours. The inhibition zone that appeared around the agar-well was measured for the indication of the presence of antimicrobial activity.
