In recent years, innovative materials have advanced in food safety, facilitating the rapid and accurate detection of additives and contaminants in food products. Gold nanoparticles (AuNPs) are key in this field, notably for their use as nanosensors, e.g., utilizing surface-enhanced Raman spectroscopy (SERS). Although several AuNP morphologies have been investigated for the development of these sensors, anisotropic nanostructures such as gold nanostars (AuNSs) and nanourchins (AuNUs) are among the most promising. These morphologies outperform isotropic NPs due to their branched structure and "hot points" with strong electromagnetic fields. However, it is crucial to develop eco-friendly methods for precise control over size and morphology in obtaining these Au anisotropic nanostructures while demonstrating that they are safe and effective in detecting various contaminants. In this study, we synthesized for the first time Au nanostructures, viz. nanourchins, using L-Dopa (levodopa) extract from Mucuna pruriens, and assessed their capability to detect food contaminants. We investigated the effect of several reaction parameters, namely concentrations of polyethylene glycol, gold seeds, gold salt, and L-Dopa extract, to control AuNPs morphology and size. It was found that polyethylene glycol and gold salt did not affect the morphology and size, while seed concentration significantly impacted the size of the AuNPs and the resulting morphology. Therefore, a response surface methodology (RSM) was applied using the parameters that had the most significant impact on the size and shape of the AuNPs. Our study revealed that the concentration of the gold seed emerged as a pivotal factor in determining the size of the AuNPs. In contrast, although the L-Dopa extract concentration played a relatively smaller role in size control, it demonstrated a more pronounced influence on the ultimate morphology of the AuNPs. More specifically, a low concentration of gold seeds and a high concentration of L-Dopa resulted in larger AuNUs ( ͌ 100 nm).In comparison, a high concentration of gold seeds and a low concentration of L-Dopa extract led to small-sized spherical shapes ( ͌ 32 nm). Finally, we evaluated three colloidal suspensions of AuNPs, each varying in size and the presence of protrusions (one small with a few protrusions, another small with protrusions, and a large one with protrusions), for their capability to detect specific food contaminants. All samples successfully detected methylene blue, a toxic food additive, with a detection limit of 10ˉ⁵ M. Generally, larger nanoparticles with more protrusions exhibited stronger SERS signals. These results underscore the significant potential of these AuNPs in creating efficient and selective biobased nanosensors for monitoring food safety.

A crescente necessidade de produção agrícola e a tentativa de atenuar os impactos negativos do uso intensivo de pesticidas, são desafios atuais para a segurança alimentar e dos alimentos, levando à procura de soluções tecnológicas mais sustentáveis. Os compostos convencionais apresentarem um papel fundamental na proteção das culturas e no aumento da produtividade, mas a sua utilização excessiva associa-se a contaminação ambiental, à presença de resíduos nos alimentos e ao desenvolvimento de resistências por parte de pragas e agentes patogénicos. A nanotecnologia surgiu como área com elevado potencial, com novas abordagens para melhorar a produção agrícola, diminuir a contaminação ambiental e aumentar a segurança dos alimentos. Neste contexto, pretende-se compreender de que forma esta tecnologia pode contribuir para a promoção da salubridade e da segurança alimentar, explorando-se as suas principais aplicações na agricultura e na sinalização de resíduos de pesticidas, bem como uma análise dos benefícios e dos limites associados à sua utilização. Serão descritos os desafios científicos, regulamentares e industriais que restringem a implementação desta nova tecnologia. O presente trabalho consiste numa revisão narrativa sobre o papel da nanotecnologia na melhoria da segurança alimentar e dos alimentos, com particular ênfase na sua aplicação no controlo e na monitorização de pesticidas e uso em fertilizantes. Identificando-se o potencial desta tecnologia na promoção de sistemas agroalimentares mais eficientes, seguros e sustentáveis, provando-se, simultaneamente, a importância de uma investigação contínua e do desenvolvimento de estratégias regulamentares adequadas que assegurem uma integração segura, responsável e eficaz da nanotecnologia no setor agroalimentar.

Currently, the common absorbent materials available in the market are derived from non-renewable petrochemicals sources which exhibit poor environmental biocompatibility. This lack of sustainability has driven research towards developing more biocompatible and eco-friendly alternatives natural bio-based materials for wastewater treatment, environmental remediation, food processing, medicine, nanosensors among others with low cost, and with no harmful by-products generation. As shown in this book, nanomaterials, as absorbents, offer several advantages over the conventional; due to the low-cost, high absorption capacities, less sludge regeneration and the availability of these compounds in the world. Among these, lignocellulosic biomass have attracted the attention of several industries due to the promising applications as absorbent. The main component of lignocellulosic material, namely: cellulose (natural polymer), has been applied directly as bio-sorbent in its natural form obtained from agri-food wastes (cassava bagasse, rice straw banana peel, corncob, among others).

Incidents of viral outbreaks have increased at an alarming rate over the past decades. The most recent human coronavirus known as COVID-19 (SARS-CoV-2) has already spread around the world and shown R0 values from 2.2 to 2.68. However, the ratio between mortality and number of infections seems to be lower in this case in comparison to other human coronaviruses (such as severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV)). These outbreaks have tested the limits of healthcare systems and have posed serious questions about management using conventional therapies and diagnostic tools. In this regard, the use of nanotechnology offers new opportunities for the development of novel strategies in terms of prevention, diagnosis and treatment of COVID-19 and other viral infections. In this review, we discuss the use of nanotechnology for COVID-19 virus management by the development of nano-based materials, such as disinfectants, personal protective equipment, diagnostic systems and nanocarrier systems, for treatments and vaccine development, as well as the challenges and drawbacks that need addressing.[Figure not available: see fulltext.]

Agradecimentos: The authors acknowledge N.M. Barbosa Neto for technical support and A.C.T. van Duin for discussions. This work was supported in part by the Brazilian Agencies CAPES and CNPq (Rede Brasileira de Pesquisa e Instrumentação em NanoEspectroscopia Óptica, MCTI-CNPq). The authors thank the Center of Microscopy at the Universidade Federal de Minas Gerais (www.microscopia.ufmg.br) for providing the means for the microscopy work and the Center for Computational Engineering and Sciences at Unicamp for financial support through the FAPESP/CEPID Grant #2013/08293-7. RP acknowledges FAPESP for Grants #2011/17253-3 and #2013/09536-0

Glucose sensing is an issue with great interest in medical and biological applications. One possible approach to glucose detection takes advantage of measuring changes in fluorescence resonance energy transfer (FRET) between a fluorescent donor and an acceptor within a protein which undergoes glucose-induced changes in conformation. This demands the detection of fluorescent signals in the visible spectrum. In this paper we analyzed the emission spectrum obtained from fluorescent labels attached to a protein which changes its conformation in the presence of glucose using a commercial spectrofluorometer. Different glucose nanosensors were used to measure the output spectra with fluorescent signals located at the cyan and yellow bands of the spectrum. A new device is presented based on multilayered a-SiC:H heterostructures to detect identical transient visible signals. The transducer consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n heterostructure optimized for the detection of the fluorescence resonance energy transfer between fluorophores with excitation in the violet (400 nm) and emissions in the cyan (470 nm) and yellow (588 nm) range of the spectrum. Results show that the device photocurrent signal measured under reverse bias and using appropriate steady state optical bias, allows the separate detection of the cyan and yellow fluorescence signals presented.