iBB

Proteases play a pivotal role in biological processes, from digestion, cell proliferation and differentiation to fertility. Deregulation of protease metabolism can result in several pathological conditions (i.e., cancer, neurodegenerative disorders, etc). Monitoring proteolytic activity in real-time can ultimately help us understand the role of such enzymes within a certain condition. This may contribute to an early diagnosis, the follow-up of disease progression or the development of protease-targetted treatments (e.g. the current HIV treatment). In a recent paper published in Trends in Biochemical Sciences, Rui Oliveira-Silva and colleagues from BERG, CQE and University of Aveiro review the main approaches used to develop biosensors for monitoring proteolytic activity. A comparison of the advantages and disadvantages of each approach is provided along with a discussion of their importance and promising opportunities for the integration of such sensors into Personalized Medicine.

Many metal nanoparticles exhibit plasmonic properties that can be explored in different applications. The synthesis of these nanoparticles often leads to a heterogeneous mixture in terms of sizes and shapes that needs to be fractionated to yield samples with narrow plasmon resonances. A simple method based on sucrose density gradient centrifugation has been proposed by BERG-iBB researchers and colleagues from Centro de Química Estrutural and Universidade de Aveiro for the fractionation of colloidal silver nanotriangles. The method affords particle fractions with surface plasmon resonances spanning from red to infrared spectral ranges that could be used to tune optical properties for plasmonic applications. The work is part of the PhD thesis of Rui Oliveira Silva and was published in Nanomaterials.

The surface plasmon modes of metal nanoparticles provide a way to efficiently enhance the excitation and emission from a fluorescent dye. IST (BERG-iBB, CQE) and Eindhoven University of Technology researchers employed DNA-directed assembly to prepare dimers of gold nanoparticles and used their longitudinally coupled plasmon mode to enhance the fluorescence emission of an organic redemitting dye. The top enhancement factors were above 1000-fold in 71% of the dimers, reaching almost 4000-fold in some cases. The work was published in the Journal of Physical Chemistry C.

The conjugation of dye-labelled DNA oligonucleotides with gold nanorods has been widely explored for the development of multifunctional fluorescent nanoprobes. In a recent publication in Nanoscale, BERG-iBB researchers in collaboration with colleagues from Centro de Química Estrutural and Centro de Ciências do Mar show that the functionalization route is crucial to achieve enhanced emission in dye nano-assemblies based on gold nanorods. By using a tip-selective approach for thiol attachment of dye molecules onto gold nanorods, it was possible to effectively increase the emission by more than 10-fold relatively to that of free dye. The results could improve significantly the performance of dye nano-assemblies for imaging or sensing applications.The work is part of the PhD thesis of David Botequim, which is supervised by Pedro Paulo (CQE) and Miguel Prazeres (BERG-iBB).

Porphyrins are typically weak emitters, which presents challenges to their optical detection by single-molecule fluorescence microscopy. A recent collaboration between BERG-iBB, Centro de Química Estrutural and Universidade Nova explores the enhancement effect of gold nanodimer antennas on the fluorescence of porphyrins in order to enable their single-molecule optical detection. Four meso-substituted free-base porphyrins were evaluated: two cationic, one neutral, and one anionic porphyrin. The gold nanodimer antennas are able to enhance the emission from these porphyrins by a factor of 10^5–10^6 increase in the maximum detected photon rates. This extreme enhancement is due to the combination of an antenna effect on the excitation rate that is estimated to be above 10^4-fold and an emission efficiency that corresponds to an increase of 2–10 times in the porphyrin’s fluorescence quantum yield. The work was published in the Journal of Physical Chemistry Letters, and is co-authored by David Botequim, Miguel Prazeres (BERG) and Pedro Paulo (CQE).