Experimental design and characterization of dual-antibody-conjugated all-trans retinoic acid-loaded lipid nanoparticles as a potential cancer therapy

Antibody-targeted immunotherapy has emerged in cancer therapies regarding checkpoint inhibition with monoclonal antibodies, such as anti-programmed death-ligand 1 (anti-PD-L1) either given alone or in combination. However, when given alone, it may fail to activate tumor-specific T cells. The combinational therapy of anti-PD-L1 with anti-4-1BB and all-trans retinoic acid (ATRA) has come into prominence due to disease heterogeneity, resulting in the synergistic effects associated with greater T-cell responses. This study introduces anti-PD-L1 and anti-4-1BB-conjugated ATRA-loaded solid lipid nanoparticles (SLNs), where the Design-Expert Program was applied for the optimization. Accordingly, antibody–conjugated ATRA-loaded SLNs had uniform dispersions with mean diameters of 179.6 ± 12.6 nm. The formulations achieved the encapsulation efficiency (EE %) of ATRA at 21.2 ± 1.4 %, regarding the three-dimensional response surface graph. The binding efficiency of anti-4-1BB and anti-PD-L1 antibodies were determined as 85.59 ± 7.3 % and 90.02 ± 5.4 %, respectively. The release profile of formulations indicated the biphasic release of ATRA (ie., 76 ± 4.4 %) from SLNs within 24 h via the Higuchi model. Particle size distributions of SLNs displayed a 7 % increase (i.e., 190.5 ± 7.63 nm) at 4 °C over 2 months. The experimental design of anti-PD-L1- and anti-4-1BB-conjugated- ATRA-loaded SLNs highlighted the promising strategy for the development of alternative formulations and the potential approach for further cancer therapies.