Polyethyleneimine-Modified Piezoelectric Barium Titanate of Various Sizes Reveals Improved Antibacterial Properties

The piezoelectric materials, barium titanates (BaTiO3) in various sizes 50, 200, and 500 nm, were modified with polyethyleneimine (PEI) as PEI@BaTiO3 to improve antibacterial activities. The realization of PEI modification was confirmed with the peaks appeared on the Fourier transform infrared (FTIR) spectrum of BaTiO3 nanoparticles similar to 1650 cm-1, which are assigned to N-H stretching vibrations. The isoelectric points of BaTiO3 nanoparticles increased to about pH 10 after PEI modification, which were pH 3-4 range for pristine BaTiO3 nanoparticles. BaTiO3 nanoparticles below 200 nm showed antibacterial activity against gram-negative bacteria with 25 mg/mL minimum inhibition concentration (MIC) value but determined not effectively against gram-positive pathogens. However, positively charged PEI@BaTiO3 particles render high antibacterial potency on wide range of bacteria with almost four-fold lower MIC values than pristine BaTiO3 nanoparticles. Safe concentration of BaTiO3 nanoparticles on L929 fibroblast cells was found at 100 mu g/mL with more than 90% cell viability. Cytotoxicity was slightly decreased for PEI@BaTiO3 particles, and 50 mu g/mL concentration of PEI@BaTiO3 particles could be used in vivo applications without any significant toxicity. The piezoelectric effect of pristine BaTiO3 generated a higher voltage for 50 nm particles compared to the larger particles. Also, PEI@BaTiO3 generated voltages, somewhat attenuated and rapidly decayed in time, showed high consistency.