Dual statistical modeling using Box Behnken and d-optimal designs for optimization of indocyanine green conjugated silver nanoparticles and improvement of their associated photothermal therapy for application in wound healing

Abstract

This work focuses on preparing indocyanine green (ICG) conjugated silver nanoparticles (AgNPs) for wound management; making use of AgNPs antimicrobial and wound healing capabilities that improve and synergize the photothermal based healing of the conjugated ICG. AgNPs were prepared using sodium borohydride (NaBH4) as reducing agent and ICG as a capping agent. The absorbances peaks at 400–420 and at 750–800 nm proved the ef- ficient preparation of Ag-NPs and conjugation of ICG, respectively. A Box Behnken design was used to construct a response surface study of the effect of different critical material attributes (NaBH4 and ICG concentrations and ICG volume) on critical quality attributes (Particle size (PS), poly- dispersity index (PDI) and zeta potential). The design suggested a formula (F*) with the smallest PS and PDI and the highest zeta potential with composition (2.73 mM NaBH4, 500 μg/mL ICG and 2.69 mL ICG: AgNO3). Trans- mission electron microscopy images of F* revealed spherical, dark, mono-disperse and non-aggregated particles of PS of 50- 60 nm, conveying with the zeta sizer measurements. Differential scanning calorimetry revealed the higher stability of F*, whereas FTIR showed some peaks of the oxidized form of NaBH4 indicating its effective ac- tion as a reducing agent for Ag+ forming AgNPs. The photothermal effect of F* was optimized using d-optimal design. The critical process parameters chosen were the irradiation power density, irradiation time and ICG level. The design selected process parameters (13.65 min irradiation time at 1.23 W/cm2), coded Therm*, possessing the maximum photothermal effect to be used in further in-vitro and in-vivo studies.