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In the environmental, industrial, and biomedical fields, pH monitorization is of the most importance. However, the most used type of pH sensors, glass pH-electrodes, still present limitations in their application in low volume samples and in cellular pH sensing, due to their size and invasive nature. Fluorescence-based sensors present a solution to such issues, providing a non-invasive solution to pH sensing [1]. Herein, we report the rational development of carbon dots (CDs) as a pH nanosensor, via an active surface preservation (ASP) method. Carbon dots (CDs) are carbon-based fluorescent nanoparticles with valuable properties such as high aqueous solubility, low cost, low toxicity, and good biocompatibility, with remarkable fluorescence performance, been increasingly used as fluorescent nanosensors [2]. By employing ASP strategies, the CDs will be prepared by using precursors with known active functional features. The ASP method allows the nanoparticles to retain the structural features of precursors, thus retaining their properties, without the need for costly and time-consuming post-synthesis functionalization procedures [2]. In this work, as proof-of-concept, the known pH-sensitivity of fluorescein is used to provide to the CDs a pH-based response. The resulting CDs presented reversible response by fluorescence enhancement in the range of pH from 4 to 12. The nanoparticles exhibited excellent photostability, in different pH solutions. The studied CDs were also unaffected by, either variation of ionic strength or the presence of interferent species, while being compatible with human cells. Finally, CDs were able to determine the pH of real samples. Thus, a selective pH fluorescent CDs-based nanosensor was developed. Acknowledgments: Projects PTDC/QUI-QFI/2870/2020 and UIDB/00081/2020. References:[1] Shamsipur M, Barati A, Nematifar Z (2019). J Photochem Photobiol C Photochem Rev 39:76–141[2] Hou P, Yang T, Liu H, et al (2017). Nanoscale 9:17334–17341

Carbon dots have attracted great attention from the research community given their very attractive luminescent properties. However, the recent discovery that some of these properties may result from fluorescent impurities originating from the synthesis process, and not from the carbon dots themselves, constitute a significant setback to our knowledge of these materials. Herein, we proceeded to the study of carbon dots generated from citric acid and urea via a microwave-assisted synthesis, focusing on their analysis by AFM, HR-TEM, XPS, FT-IR, ESI-MS, UV-Vis and fluorescence spectroscopy. We have found that this synthesis process does generate molecular fluorophores that can mask the luminescence of the carbon dots. More importantly, our data demonstrates that when present in the same solution, the carbon dots and these fluorophores do not behave as separated species with individual emission. Instead, they interact to produce a hybrid luminescence, which excited state properties and reactivity are different from the properties of the individual species. These results indicate the possibility for the development of hybrid materials composed by carbon dots and related molecular fluorophores with new and improved properties.

Diabetic foot ulcers (DFUs) are a serious complication from diabetes mellitus, with a huge economic, social and psychological impact on the patients life. One of the main reasons why DFUs are so difficult to heal is related to the presence of biofilms. Biofilms promote wound inflammation and a remarkable lack of response to host defences/treatment options, which can lead to disease progression and chronicity. In fact, appropriate treatment for the elimination of these microbial communities can prevent the disease evolution and, in some cases, even avoid more serious outcomes, such as amputation or death. However, the detection of biofilm-associated DFUs is difficult due to the lack of methods for diagnostics in clinical settings. In this review, the current knowledge on the involvement of biofilms in DFUs is discussed, as well as how the surrounding environment influences biofilm formation and regulation, along with its clinical implications. A special focus is also given to biofilm-associated DFU diagnosis and therapeutic strategies. An overview on promising alternative therapeutics is provided and an algorithm considering biofilm detection and treatment is proposed., This work was supported by: Base Funding—UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy—LEPABE—funded by national funds through the FCT/MCTES (PIDDAC); Project Biocide_for_Biofilm-PTDC/BII-BTI/30219/2017- POCI-01-0145-FEDER-030219, ABFISH–PTDC/ASP-PES/28397/2017-POCI-01-0145-FEDER- 028397 and Germirrad-POCI-01-0247-FEDER-072237, funded by FEDER funds through COMPETE2020— Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PID DAC) through FCT/MCTES. The authors also thank the CITAB (Centre for the Research and Technol ogy of Agro-Environmental and Biological Sciences) under the scope of the FCT funds with reference UIDB/AGR/04033/2020. Ana Afonso (2020.04773.BD) and Diana Oliveira (SFRH/BD/138217/2018) acknowledge the FCT grants. Anabela Borges thanks the FCT for the financial support of their work contract through the Scientific Employment Stimulus—Individual Call—[CEECIND/01261/2017]., info:eu-repo/semantics/publishedVersion

The establishment of a sessile community is believed to occur in a sequence of steps where genetically distinct bacteria can become attached to partner cells via specific molecules, in a process known as coaggregation. The presence of bacteria with the ability to autoaggregate and coaggregate has been described for diverse aquatic systems, particularly freshwater, drinking water, wastewater, and marine water. In these aquatic systems, coaggregation already demonstrated a role in the development of complex multispecies sessile communities, including biofilms. While specific molecular aspects on coaggregation in aquatic systems remain to be understood, clear evidence exist on the impact of this mechanism in multispecies biofilm resilience and homeostasis. The identification of bridging bacteria among coaggregating consortia has potential to improve the performance of wastewater treatment plants and/or to contribute for the development of strategies to control undesirable biofilms. This study provides a comprehensive analysis on the occurrence and role of bacterial coaggregation in diverse aquatic systems. The potential of this mechanism in water-related biotechnology is further described, with particular emphasis on the role of bridging bacteria., This work was financially supported by: Base Funding UIDB/00511/2020 of LEPABE and UIDB/00081/2020 of CIQUP funded by national funds through the FCT/MCTES (PIDDAC); Project Biocide_for_Biofilm-PTDC/BII-BTI/30219/2017-POCI-01-0145-FEDER 030219, ABFISH–PTDC/ASP-PES/28397/2017-POCI-01-0145-FEDER 028397 and ALGAVALOR-POCI-01-0247-FEDER-035234, funded by FEDER funds through COMPETE2020–Programa Operacional Com petitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. This study was further supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors also thank to CITAB (Centre for the Research and Technology of Agro-Environmental and Biological Sciences) under the scope of the FCT funds with reference UIDB/AGR/04033/2020. Ana Afonso acknowledges the FCT grant 2020.04773.BD., info:eu-repo/semantics/publishedVersion