Effect of Crosslinking Using Heat on the Physicochemical Features of Bsa–Capsaicin Nanoparticles

<b>Background/Objectives</b>: The synthesis of protein nanoparticles (NPs) using the coacervation method is influenced by critical parameters. The use of glutaraldehyde limits the pharmacological applications of NPs in humans due to the potential toxicity of residual aldehydes that remain after the purification of the nanoparticles. The aim was to assess heat effect as a crosslinking agent for the synthesis of bovine serum albumin (BSA)-capsaicin nanoparticles and its effect on the physicochemical characteristics of nanoparticles. <b>Results</b>: The initial concentrations of BSA and capsaicin in the formulation were directly correlated with the amount of BSA that was transformed into nanoparticles and the loaded capsaicin (<i>r</i> = 0.97, <i>p</i> = 0.0003 and <i>r</i> = 0.95, <i>p</i> = 0.0003), respectively. Furthermore, the morphometric parameters of nanoparticles were affected by the increase in capsaicin concentration, but not by temperature. The nanoparticles increased in dimensions and showed a loss of shape due to coalescence between nanoparticles. The ζ-potential decreased with the increase in the concentration of capsaicin added. This effect compromised the stability of the nanoparticles; on the other hand, molecular interactions were observed between hydrophobic residues of phenylalanine and tyrosine in BSA and the hydrophobic moiety of capsaicin. At the same time, BSA nanoparticles showed a potential for disassembling and delivering the payload capsaicin, which caused an antisteatotic effect in the liver of a murine model. <b>Conclusions</b>: heat (70 °C) can replace crosslinking agents, such as glutaraldehyde. This property is particularly useful when an aldehyde-free synthesis of BSA nanoparticles is needed.