Design and characterisation of casein coated and drug loaded magnetic nanoparticles for theranostic applications.

Theranostic systems enable early cancer diagnostic and treatment. In this work, we prepared Na-caseinate coated magnetic nanoparticles (MNP) to assess their capability as a theranostic system. This system enables monitoring by magnetic particle imaging (MPI), drug delivery and magnetic hyperthermia. MNP were synthesized in a continuous flow, coated with Na-caseinate and enzymatically crosslinked with transglutaminase to increase their colloidal stability and enable drug loading. They were investigated concerning their magnetic behaviour by DC magnetization measurements (DCM), magnetic particle spectroscopy (MPS) and AC-magnetometry to evaluate their suitability for MPI and hyperthermia. Further, their stability in different salt solutions as well as their encapsulation efficiency with a hydrophobic model drug (nile red), cell viability and uptake were investigated. Our results show that the Na-caseinate coating of MNP marginally effects the magnetic behaviour of the MNP with a consistent magnetization saturation M S of 109(5) A m2 per kg(Fe) for uncoated and casein coated MNP and with a decrease of <15% of A 3*, but only a slight decrease of 2% of A 5/A 3 for Na-caseinate coated MNP. Furthermore, the Na-caseinate coating of MNP increased their salt stability, under unchanged magnetic behaviour. Drug loading (up to ∼75%) and release kinetics such as the delivery into cutaneous squamous cell carcinoma cells (SCL-1) was shown. Our results demonstrate that casein coated MNP are highly promising candidates for theranostic applications in drug delivery, magnetic hyperthermia and magnetic particle imaging.

Colorimetric detection of oral bacteria using functionalized gold nanoparticles as a plasmonic biosensor array.

Early detection of specific oral bacterial species would enable timely treatment and prevention of certain oral diseases. In this work, we investigated the sensitivity and specificity of functionalized gold nanoparticles for plasmonic sensing of oral bacteria. This approach is based on the aggregation of positively charged gold nanoparticles on the negatively charged bacteria surface and the corresponding localized surface plasmon resonance (LSPR) shift. Gold nanoparticles were synthesized in different sizes, shapes and functionalization. A biosensor array was developed consisting of spherical- and anisotropic-shaped (1-hexadecyl) trimethylammonium bromide (CTAB) and spherical mercaptoethylamine (MEA) gold nanoparticles. It was used to detect four oral bacterial species (Aggregatibacter actinomycetemcomitans, Actinomyces naeslundii, Porphyromonas gingivalis and Streptococcus oralis). The plasmonic response was measured and analysed using RGB and UV-vis absorbance values. Both methods successfully detected the individual bacterial species based on their unique responses to the biosensor array. We present an in-depth study relating the bacteria zeta potential and AuNP aggregation to plasmonic response. The sensitivity depends on multiple parameters, such as bacterial species and concentration as well as gold nanoparticle shape, concentration and functionalization.