Surface hydrophobicity of microparticles modulates adjuvanticity

Area of Science:

• Biomaterials Science
• Immunology
• Vaccine Development

Background:

• Polymeric microparticles are effective vaccine adjuvants, modulating immune responses through physicochemical properties.
• Surface properties, particularly hydrophobicity, are critical for microparticle function, but their impact on adjuvanticity is not well understood.

Purpose of the Study:

• To investigate the correlation between microparticle surface hydrophobicity and adjuvanticity.
• To evaluate how varying surface hydrophobicity affects immune cell interactions and in vivo immune responses.

Main Methods:

• Preparation of poly(d,l-lactic acid) (PLA), poly(d,l-lactic-co-glycolic acid) (PLGA), and poly(monomethoxypolyethylene glycol-co-d,l-lactide) (PELA) microparticles with controlled surface hydrophobicity using premix membrane emulsification.
• In vitro assessment of antigen uptake by dendritic cells (DCs), and expression of MHC II and CD86.
• In vivo evaluation of cytokine secretion from splenocytes of vaccinated mice.
• Adhesion force measurements to quantify microparticle-cell membrane interactions.

Main Results:

• Increased surface hydrophobicity of PLA microparticles enhanced antigen internalization into DCs and upregulated MHC II and CD86 expression.
• In vivo studies demonstrated that higher microparticle hydrophobicity significantly boosted splenocyte cytokine secretion in vaccinated mice.
• Adhesion force measurements confirmed that increased hydrophobicity strengthens interactions between microparticles and cell membranes, facilitating cellular uptake.

Conclusions:

• Microparticle surface hydrophobicity is a critical determinant of vaccine-induced immune response magnitude.
• Optimizing microparticle hydrophobicity can enhance the efficacy of particulate vaccine systems.