Influence Of Nanoparticles And Electrospun Fibers On The Immune Activation Of Macrophages

Nano-biomaterials are widely used in many biomedical fields.However,most engineered nano-biomaterials have presented non-negligible immunotoxicity.On one hand,a proper degree of immune response might be beneficial to tissue repair and regeneration,because it is supposed that the function of immune cells should be activated via the interaction between the cells and biomaterials.On the other hand,recognition and rejection of the organisms towards injected or inplanted biomaterials should be avoided.Thus,the specific patterns of inflammatory-activating behaviors of biomaterials should be unrevealed in a more systematic way.In this work,gold nanoparticles(GNPs)with 3 different diameters were prepared,and then were further modified with poly(ethylene glycol)(PEG)or chicken ovalbumin(OVA)to achieve different surface properties.Both types of GNPs had sizes of 12,35 and 60 nm and possessed negatively charged surface,showing good colloidal stability in cell culture medium,respectively.The conjugated amount of OVA was around 110 ng/mm2 regardless of the particle size.All the particles showed neglectable influence on viability of RAW264.7 macrophages when being cocultured in vitro.The GNPs of a larger size or conjugated with OVA.were internalized with significantly larger amount.While the OVA.-coated GNPs induced higher secretion of tumor necrosis factor-?,interleukin-6,and interleukin-1?,the PEG coating did not induce significant inflammatory response especially when the size of NPs was larger than 35 nm.Comparatively,smaller GNPs induced stronger inflammatory responses regardless of their surface-conjugated molecules.Poly(lactide-co-glycolide)(PLGA)is one of the most satisfactory polymer materials with good biocompatibility,degradability and utility.Various matters can be loaded into PLGA NPs by conjunction,adsorption or doping while bioactivity is still maintained.In this work,PLGA NPs with 3 different molecular weights were fabricated by using bovine serum albumin(BSA)and polyethyleneimine(PEI)as the dispersing agents,respectively.The PEI/PLGANPs did not show significant immune activation in terms of secretion of inflammatory cytokines such as tumor necrosis factor-?(TNF-?),interleukin-6(IL-6),and interleukin-1?(IL-1?)too.By contrast,the BSA/PLGA NPs induced significantly higher expression of TNF-a,likely due to the heterogeneous albumin and contaminated involved endotoxin and the synergistic role of larger uptake of the BSA/PLGA NPs by macrophages.Considering the morphology of electrospun fibers might present influences on the adhesion,proliferation or differenciation of cells,the immune-activating behavior of electrospun fibers with various diameters or alignments was studied.In this chapter,PLGA electrospun nanofibers with different diameters and alignments were prepared and applied to evaluate the immune activating potential towards RAW264.7 cells and abdominal primary macrophages.Results show that no obvious cytotoxicity was observed,and a nonnegligible inflammation was detected for both RAW264.7 and macrophages.The electrospun PLGA nanofibers showed 4-7 fold of TNF-a secretion level for RAW264.7 cells compared with the control group.Though the 900 nm-Aligned PLGA electrospun fiber exhibited the most obvious "contact induction effect",but it did not induce any differentiation towards RAW264.7 cells,indicating that the shape change of cells is not necessarily related to the phenotype changeing.Besides,the co-incubation of PLGA electrospun fibers with macrophages indicated that only the 900 nm-Aligned PLGA electrospun fiber was preferable for the polarization of macrophages to M1 phenotype.Therefore,to achieve desirable immuno-response of NPs,the particle size,surface coating and protein types should be taken into consideration.For the inert design,the NPs with a larger size and PEG coating are preferable,and NPs with a proper amount of positively charged coating are even better.While for the immunomodulating design,the NPs with a smaller size and antigen coating(OVA or endotoxin contaminated proteins)can achieve the better role.Moreover,the electrospun nanofibers with a smaller diameter and aligned direction are better to be applied in a long term circumstance because of its stability and low rejection reaction.