## 1 Introduction  
Recent studies have focused on the contamination of aquatic and terrestrial environments because of disposable soft contact lenses [1, 2]. Studies show that approximately 80% of soft contact lens wearers use disposable contact lenses. It was found that approximately 80% of the used disposable contact lenses are thrown away in the trash, and approximately 20% are washed away in kitchen drains and toilets. Contact lenses do not entirely decompose in sewage treatment plants because of their low biodegradability. The generated sludge, including undecomposed contact lenses, causes microplastic pollution because it is disposed of in coastal waters or used in agricultural soils. Silcone-based hydrogels are the most common soft contact lens material, accounting for approximately 64% of the US market [3]. Because of their porous nature, silicones have the highest oxygen permeability among all contact lens materials. Furthermore, silicone soft contact lenses are highly durable and have a higher modulus of elasticity than conventional polymer hydrogels. However, they have been reported not to degrade in chemical or biological treatments, although they physically break down and become smaller in sewage treatment plants. Poly (2-hydroxyethyl methacrylate (pHEMA) has also been widely used as a material for commercial soft contact lenses [3, 4, 5]. pHEMA-based hydrogels are transparent and soft and have high oxygen permeability and, thus, have excellent properties related to corneal hypoxia. However, the adsorption of proteins is an issue for pHEMA hydrogels [6, 7]. It has been reported that the charge and porosity (water content) of the gels affect the adsorption and permeation of proteins [8; 9]. In addition, monomers, such as methyl methacrylate and \(N\)-vinyl pyrrolidone, which are also used in commercially available contact lenses, have been reported to increase protein deposition. With the objective of producing a sustainable society, the use of environmentally friendly plant-derived materials has recently attracted significant attention. A classic example is the use of plant-derived materials for disposable shopping bags and drinking straws that are used in significant quantities. Furthermore, polylactic acid trash bags made from corn and water-absorbent disposable diapers made from cellulose have been developed [10; 11]. In addition, cellulose derivatives, which are potential water absorbents, are also used in medical materials, such as wound dressings and drug delivery systems [12; 13]. However, no studies have been published on soft contact lens materials containing cellulose or cellulose derivatives as the primary components. The irradiation effects of quantum beams such as electron beams and \(\gamma\)-rays on proteins, especially on the mechanism of a crosslinking reaction, have been investigated, and various materials for medical applications have been developed using such irradiation techniques. Protein hydrogels have been prepared as scaffolding materials for the three-dimensional culture of cells [14] and contrast agents for magnetic resonance imaging diagnostics [15]. These hydrogels have also been used to produce cell sheets on which cells form three-dimensional structures by themselves [16] and materials for preventing organ adhesion after abdominal surgery [17]. Cellulose is the most abundant natural organic polymer on earth. Although cellulose has low solubility in water and most organic solvents, it can be chemically modified to make it highly functional, and hydrogel materials for use in biological and medical fields have been created [18]. Various hydrogels have been prepared using radiation-crosslinking cellulose derivatives [19; 20; 21]. Gel dosimeters for radiotherapy have been developed using a reaction in transparent hydroxypropyl cellulose (HPC) gels [22; 23]. Based on these findings, we developed hydrogels for fabricating environmentally friendly soft contact lenses using radiation processing techniques.