Antimicrobial properties of spray-dried cellulose nanocrystals and metal oxide-based nanoparticles-in-microspheres

Spray-dried nanoparticle-in-microsphere formulations, composed of aluminum oxide nanoparticles (NPs), zinc oxide, zinc oxide NPs and cellulose nanocrystals (CNCs), with potent antimicrobial and antibiofilm activity against Gram-negative and Gram-positive bacteria are reported. The study highlights the role of matrix compositions (ratios) in manipulating metal oxide biomaterials' antimicrobial properties and toxicity. The antimicrobial activity of nanoparticle-in-microsphere was higher than each raw material used. A formulation composed of CNCs (weight % >= 0.75%) and an equal weight % of aluminum oxide and zinc oxide NPs (similar to 0.25% per type of NPs) produced the highest antimicrobial and antibiofilm activity. Interestingly, the toxicity of these formulations, tested against peripheral blood mononuclear cells, was very minimal (<= 500 mu g/ml) and significantly lower than the toxicity of the metal oxide NPs when tested alone. Nanoparticles-in-microspheres with low toxicity and high antimicrobial properties could be employed in target drug delivery to bypass antibiotics.