Synthesis of immunomodulatory biomimetic lipid polymer hybrid nanoparticles and application of zebrafish larvae in immunomodulation screening

Since the antibiotic golden era of the mid-20th century, there have been limited antibiotics approved, while antibiotic resistance continues to escalate disproportionately, outpacing the rate of novel antibiotic discovery. This imbalance poses a serious global health concern, with an estimated annual death toll of 10 million due to antibiotic resistance by 2050. There is a growing interest in immunotherapy as an alternative approach to conventional antibiotics due to its ability to target and stimulate immune system, leveraging its innate ability to self-eradicate pathogens. This study synthesized lipid polymer hybrid nanoparticles (LPHNPs) conjugated with two immunomodulatory agents, namely, curdlan and mycolic acid (MA), as a potential immunotherapy for bacterial infections. LPHNPs were synthesized using lecithin and polycaprolactone (PCL) at a 15 % lipid-to-polymer (w/w) ratio. Additionally, PCL-curdlan copolymer, comprising 15 % w/w curdlan, was successfully synthesized and used to conjugate the LPHNPs with various curdlan concentrations. Furthermore, The LPHNPs were conjugated with varying MA concentrations, with or without curdlan. In-vivo assessment of the immunomodulatory effect of the LPHNPs was conducted using a larval zebrafish model assessing behaviour and immunofluorescence, as indicators of immune stimulation. The data suggests that curdlan exhibits a more complex immunoregulatory role as demonstrated by the countered stimulated behavioural effect while inflammation remained heightened. This work also provides new insights that zebrafish larvae are a valuable screening tool in the development of nanoparticle immunotherapies.