Noble metal nanomaterials, such as gold or silver nanoparticles, exhibit unique photonic, electronic, catalytic and therapeutic properties. The high versatility in their synthesis, especially size and shape features, as well as in the surface functionalization by, e.g., physisorption, direct chemisorption of thiol derivatives and covalent binding through bifunctional linkers or specific affinity interactions, prompted their widespread and rising use as multifunctional platforms for theranostic purposes. In this paper, the recent developments of gold and silver nanoparticles for application in biosensing, medical imaging, diagnosis and therapy is reviewed from the following five aspects: (1) the gold and silver nanomaterials intrinsic properties of biomedical interest; (2) the synthesis of noble metal nanoparticle by chemical, physical and biological/green processes; (3) the applications of gold and silver nanoparticles in imaging, diagnostic and therapeutic mode; (4) the surface functionalization processes for targeting, controlled drug loading and release, triggered pathways of cellular uptake and tissue distribution; and (5) nanotoxicity. The historical developments and the most recent applications have been focused on, together with suggested strategies for future more efficacious, targeted delivery.

Heme proteins take part in a number of fundamental biological processes, including oxygen transport and storage, electron transfer, catalysis and signal transduction. The redox chemistry of the heme iron and the biochemical diversity of heme proteins have led to the development of a plethora of biotechnological applications. This work focuses on biosensing devices based on heme proteins, in which they are electronically coupled to an electrode and their activity is determined through the measurement of catalytic currents in the presence of substrate, i.e., the target analyte of the biosensor. After an overview of the main concepts of amperometric biosensors, we address transduction schemes, protein immobilization strategies, and the performance of devices that explore reactions of heme biocatalysts, including peroxidase, cytochrome P450, catalase, nitrite reductase, cytochrome c oxidase, cytochrome c and derived microperoxidases, hemoglobin, and myoglobin. We further discuss how structural information about immobilized heme proteins can lead to rational design of biosensing devices, ensuring insights into their efficiency and long-term stability.

Multifunctional nanoparticles (NPs) are an advantageous scaffold for assembling hybrid bio-inorganic nanoplatforms, with impact on key technologies, including molecular diagnostics, therapeutics, bioengineering, biocatalysis, energy generation and storage. In the present work we used core–shell silica NPs, coumarin-doped in the core and surface-tailored with different chemical moieties (–PEG, –COOH, –NH₂), as a possible nanocarrier for drug delivery and imaging. The nanoparticle surface was further decorated with lipid bilayers by the interaction with fluorescent small unilamellar lipid vesicles bearing different charges, namely zwitterionic (PC), anionic (PS25) and cationic (EPC25). The fluorescence energy transfer (FRET) processes between the silica nanoparticles and the lipid bilayers, dye-labelled with nitrobenzoxadiazole and/or rhodamine fluorescent moieties, were investigated to exploit the behaviour of the hybrid biomembrane–NP assembly as a theranostic nanocarrier. A relevant role of electrostatic interactions to influence the photophysical properties of the hybrid lipid–NP systems resulted. In proof-of-concept cellular experiments, an increased cellular internalization of NP–PEG/PS25 and NP–NH₂/PS25 compared to the respective bare nanoparticles was observed, as well as a decreased cellular uptake, both in the nuclei and in the cytoplasm, in both NP–PEG/EPC25 and NP–COOH/EPC25 systems with respect to the cationic lipids alone. Moreover, intracellular FRET processes were detected by in vitro cell imaging with confocal microscopy, emphasizing the potentialities of such nanoplatforms in theranostic applications.

Vibrational spectroscopy and in particular, resonance Raman (RR) spectroscopy, can provide molecular details on metalloproteins containing multiple cofactors, which are often challenging for other spectroscopies. Due to distinct spectroscopic fingerprints, RR spectroscopy has a unique capacity to monitor simultaneously and independently different metal cofactors that can have particular roles in metalloproteins. These include e.g., (i) different types of hemes, for instance hemes c, a and a₃ in caa₃-type oxygen reductases, (ii) distinct spin populations, such as electron transfer (ET) low-spin (LS) and catalytic high-spin (HS) hemes in nitrite reductases, (iii) different types of Fe-S clusters, such as 3Fe-4S and 4Fe-4S centers in di-cluster ferredoxins, and (iv) bi-metallic center and ET Fe-S clusters in hydrogenases. IR spectroscopy can provide unmatched molecular details on specific enzymes like hydrogenases that possess catalytic centers coordinated by CO and CN⁻ ligands, which exhibit spectrally well separated IR bands. This article reviews the work on metalloproteins for which vibrational spectroscopy has ensured advances in understanding structural and mechanistic properties, including multiple heme-containing proteins, such as nitrite reductases that house a notable total of 28 hemes in a functional unit, respiratory chain complexes, and hydrogenases that carry out the most fundamental functions in cells.