Biodegradable adhesives prepared using three different forms of soy protein-based products (defatted soy flour/soy protein concentrate/soy protein isolate), sodium hydroxide, and itaconic acid polyamidoamine-epichlorohydrin (IA-PAE) with 0 wt%-20 wt% substitution rates were utilized to enhance the production of mangrove wood composites. H nuclear magnetic resonance, differential scanning calorimetry, and ultra-high-resolution field emission scanning electron microscopy were employed to characterize the composite samples. Other measurements involved the determination of viscosity, pH, physical, mechanical, dimensional stability, CT numbers, and relative electron density parameters. The ideal curing conditions for the composite bio-adhesives were found to be 15 wt% IA-PAE, 602.50 ± 172.21-391.11 ± 105.82 mPa s, pH 11.0, 180 °C, and 18 min, respectively. The improved physiochemical characteristics of DSF, SPC, and SPI confirmed that NaOH/IA-PAE was integrated into the adhesive system and ameliorated the overall performance of the resulting composites. The results showed that all composite samples, except for those bonded with 0 wt% and 5 wt% IA-PAE, matched up with the quality specification stated in the JIS A-5908 and ASTM D1037. Samples D1, D2, and D3 exhibited optimum characteristics, demonstrating their uses in the development of low-toxicity and sustainable reference tissue substitute phantom in radiological areas.