I have an idea for an organism i want to make, but to produce them i will likely need a vector that is no more than about 100 nm in diameter. I have been considering using BSA-PEI particles, but i realized the imaging was done with TEM, performed in a dry environment, meaning the size is reduced compared to reality when it's in solution and the real size of about 160 nm may be slightly too large. Also considered just straight PEI, but the transfection efficiency drops significantly as the particle size approaches the 100 nm range. These organisms embryos are rather fragile and I'd like to avoid stressful conditions, so i can't use electroporation. I'd appreciate any input in this conundrum. Thanks.