Protein–nanoparticle hybridization can ideally lead to novel biological entities characterized by emerging properties that can sensibly differ from those of the parent components. Herein, the effect of ionic strength on the biological functions of recombinant His-tagged spermine oxidase (i.e., SMOX) was studied for the first time. Moreover, SMOX was integrated into colloidal surface active maghemite nanoparticles (SAMNs) via direct self-assembly, leading to a biologically active nano-enzyme (i.e., SAMN@SMOX). The hybrid was subjected to an in-depth chemical–physical characterization, highlighting the fact that the protein structure was perfectly preserved. The catalytic activity of the nanostructured hybrid (SAMN@SMOX) was assessed by extracting the kinetics parameters using spermine as a substrate and compared to the soluble enzyme as a function of ionic strength. The results revealed that the catalytic function was dominated by electrostatic interactions and that they were drastically modified upon hybridization with colloidal ɣ-Fe₂O₃. The fact that the affinity of SMOX toward spermine was significantly higher for the nanohybrid at low salinity is noteworthy. The present study supports the vision of using protein–nanoparticle conjugation as a means to modulate biological functions.

The dispersion of antibiotics in livestock farming represents a health concern worldwide, contributing to the spread of antimicrobial-resistant bacteria through animals, the environment, and humans. Phenolic compounds could be alternatives to antibiotics, once drawbacks such as their low water solubility, bioavailability, and reduced stability are overcome. Although nano- or micro-sized formulations could counter these shortcomings, they do not represent cost-effective options. In this study, three phenolic compounds, obtained from wood-processing manufacturers, were characterized, revealing suitable features such as their antioxidant activity, size, and chemical and colloidal stability for in-field applications. The minimum inhibitory concentration (MIC) of these colloidal suspensions was measured against six bacterial strains isolated from livestock. These particles showed different inhibition behaviors: Colloidal chestnut was effective against one of the most threatening antibiotic-resistant pathogens, i.e., S. aureus, but ineffective toward E. coli. Instead, colloidal pine showed a weak effect on S. aureus but specificity toward E. coli. The present proof-of-concept points at colloidal polyphenols as valuable alternatives for antimicrobial substitutes in the livestock context.

DNA is an exceptional building block for the fabrication of dynamic supramolecular systems with switchable geometries. Here, a self-assembled, tunable plasmonic–fluorescent nanostructure was developed. A precise sliding motion mechanism was operated through the control of strand displacement reactions, shifting two single-strand DNA (ssDNA) rails connected by a ssDNA quasi-ring structure. The system was reconfigured as a nano-mechanical structure, generating six discrete configurations, and setting specific distances between a tethered gold nanoparticle (AuNP) and a fluorophore, Sulfo-Cyanine3 (Cy3). Each configuration produced a distinct fluorescence emission intensity via plasmonic quenching/enhancement effects, and therefore the structure behaved as a nano-ruler. To optimize the system, the reversible distance-dependent fluorescence quenching or enhancement phenomena were investigated by testing AuNPs with diameters of 5, 10, and 15 nm, yielding the best performances with 10 nm AuNPs. Furthermore, a geometric model of the system was produced, confirming the observed results. The fluorophore–plasmonic surface positioning, conferred by the DNA ruler, led to a finite state nano-machine with six alternative signal outputs. This mechanism, working as a fluorescent reporter, could find application in a multiple-responsive detection system of single-strand nucleic acids, such as viruses or microRNAs.

Protein–nanoparticle hybridization can ideally lead to novel biological entities characterized by emerging properties, which can sensibly differ from those of the parent components. Herein, the effect of ionic strength on the biological functions of recombinant, His-tagged spermine oxidase (i.e., SMOX) was studied for the first time. Moreover, SMOX was integrated to colloidal surface active maghemite nanoparticles (SAMNs) by direct self-assembly, leading to a biologically active nano-enzyme (i.e., SAMN@SMOX). The hybrid was subjected to an in-depth chemical-physical characterization highlighting that protein structure was perfectly preserved. The catalytic activity of the nanostructured hybrid (SAMN@SMOX) was assessed by extracting kinetics parameters using spermine as substrate and compared to the soluble enzyme as a function of ionic strength. Results revealed that the catalytic function was dominated by electrostatic interactions and that they were drastically modified upon hybridization with colloidal ɣ-Fe2O3. Noteworthy, the affinity of SMOX toward spermine was significantly higher for the nanohybrid at low salinity. The present study supports the vision of using protein–nanoparticle conjugation as a mean for modulating biological functions.

Non-coding RNAs belong to a heterogenous family that, among other functions, acts as a biomolecular regulator of gene expression. In particular, lncRNAs, which are estimated to be as numerous as coding RNAs in humans, are thought to interact with genomic DNA to form triple helices. However, experimental evidence of their involvement with processes, such as chromatin structure dynamics or RNA transcription, is still missing. Here, a mechanism of transcription enhancement/inhibition is described, where hybrid RNA-DNA triplexes regulate transcription rates in Escherichia coli promoter-based designed architectures. Sequences associated with triplexes were identified in a library of bacterial promoters and characterized in vitro, followed by a synthetic biology approach to verify their ability to control transcription and translation. A model of the triplex-promoter complex was produced showing that transcription enhancement is due to a distortion of the duplex DNA as a consequence of its conjugation with RNA in the triplex assembly. These results point at a mechanism of RNA function that is still unknown and could be common in more complex organisms, such as metazoans including mammals, where non-coding RNAs are more abundant and are believed to play a fundamental role in determining hetero/euchromatin and transcription modulation.

Dispersion of antibiotic in livestock farming represents a health concern worldwide, contributing to the spread of antimicrobial resistant bacteria through animals, the environment, and humans. Phenolic compounds could be alternatives to antibiotics, once drawbacks such as low water solubility, bioavailability, and reduced stability are overcome. Although nano- or microsized formulations could respond to these shortcomings they do not represent cost-effective options. Here, three phenolic compounds, obtained from wood processing manufacturers, were characterized, revealing suitable features such as antioxidant activity, size, and chemical and colloidal stability for in-field applications. The Minimum Inhibitory Concentration (MIC) of these colloidal suspensions was measured against six bacterial strains isolated from livestock. These particles showed different inhibition behaviors: Colloidal chestnut was effective against one of the most threatening antibiotic resistant pathogens such as S. aureus but was ineffective toward E. coli. On the other hand, colloidal pine showed a weak effect on S. aureus but specificity toward E. coli. The present proof-of-concept points at colloidal polyphenols as valuable alternatives for antimicrobial substitutes in the livestock context.