Some applications, in particular, wound dressings, require significant water holding capability: hydrogels formed from Basil seed mucilage (BSM) are non-toxic natural substances and exhibit the needed water holding capacity. However, the sponges have low dimensional stability and easily degrade in aqueous media. We overcame this drawback by crosslinking with borax. To provide antibacterial activity, zinc oxide nanoparticles (ZnO-NP) were added. With 10-20 wt% added borax and ZnO-NP, all key properties improved: dimensional stability, water retention capacity (31 to 41%), stress at maximum load (2.6 to 6.6 MPa), Young's modulus (74 to 113 MPa) and strain (28 to 54%). An interconnecting system of pores with well distributed ZnO-NP was observed from scanning electron microscope. In addition, higher borax and ZnO-NP loadings slightly decreased porosity (92% to 73%) and swelling (109 to 56). Moreover, antibacterial activity and cytotoxicity of BSM hydrogel sponge were also examined.