Advances in surface design and biomedical applications of magnetic nanoparticles

Despite significant efforts by scientists in the development of advanced nanotechnology materials for smart diagnosis devices and drug delivery systems, the success of clinical trials remains largely elusive. In order to address this biomedical challenge, magnetic nanoparticles (MNPs) have gained attention as a promising candidate due to their theranostic properties, which allow the simultaneous treatment and diagnosis of a disease. Moreover, MNPs have advantageous characteristics such as a larger surface area, high surface-to-volume ratio, enhanced mobility, mass transference and, more notably, easy manipulation under external magnetic fields. Besides, certain magnetic particle types based on the magnetite (Fe3O4) phase have already been FDA-approved, demonstrating biocompatible and low toxicity. Typically, surface modification and/or functional group conjugation are required to prevent oxidation and particle aggregation. A wide range of inorganic and organic molecules have been utilized to coat the surface of MNPs, including surfactants, antibodies, synthetic and natural polymers, silica, metals, and various other substances. Furthermore, various strategies have been developed for the synthesis and surface functionalization of MNPs to enhance their colloidal stability, biocompatibility, good response to an external magnetic field, etc. Both uncoated MNPs and those coated with inorganic and organic compounds exhibit versatility, making them suitable for a range of applications such as drug delivery systems (DDS), magnetic hyperthermia, fluorescent biological labels, biodetection and magnetic resonance imaging (MRI). Thus, this review provides an update of recently published MNPs works, providing a current discussion regarding their strategies of synthesis and surface modifications, biomedical applications, and perspectives.

A comprehensive review on enzyme-based biosensors: Advanced analysis and emerging applications in nanomaterial-enzyme linkage

Biosensors with nanomaterials and enzymes detect and quantify specific targets in samples, converting recognition into measurable signals. The study explores the intrinsic synergy between these elements for detecting and quantifying particular targets in biological and environmental samples, with results demonstrated through bibliometric analysis and a comprehensive review of enzyme-based biosensors. Using WoS, 57,331 articles were analyzed and refined to 880. Key journals, countries, institutions, and relevant authors were identified. The main areas highlighted the multidisciplinary nature of the field, and critical keywords identified five thematic clusters, revealing the primary nanoparticles used (CNTs, graphene, AuNPs), major application fields, basic application themes, and niche topics such as sensitive detection, peroxidase activity, and quantum dot utilization. The biosensor overview covered nanomaterials and their primary applications, addressing recent advances and inherent challenges. Patent analysis emphasized the U.S. leadership in the industrial sector, contrasting with China's academic prominence. Future studies should focus on enhancing biosensor portability and analysis speed, with challenges encompassing efficient integration with recent technologies and improving stability and reproducibility in the nanomaterial-enzyme interaction.

Enhancing biocatalyst performance through immobilization of lipase (Eversa® Transform 2.0) on hybrid amine-epoxy core-shell magnetic nanoparticles

Magnetic nanoparticles were functionalized with polyethylenimine (PEI) and activated with epoxy. This support was used to immobilize Lipase (Eversa® Transform 2.0) (EVS), optimization using the Taguchi method. XRF, SEM, TEM, XRD, FTIR, TGA, and VSM performed the characterizations. The optimal conditions were immobilization yield (I.Y.) of 95.04 ± 0.79 %, time of 15 h, ionic load of 95 mM, protein load of 5 mg/g, and temperature of 25 °C. The maximum loading capacity was 25 mg/g, and its stability in 60 days of storage showed a negligible loss of only 9.53 % of its activity. The biocatalyst demonstrated better stability at varying temperatures than free EVS, maintaining 28 % of its activity at 70 °C. It was feasible to esterify free fatty acids (FFA) from babassu oil with the best reaction of 97.91 % and ten cycles having an efficiency above 50 %. The esterification of produced biolubricant was confirmed by NMR, and it displayed kinematic viscosity and density of 6.052 mm2/s and 0.832 g/cm3, respectively, at 40 °C. The in-silico study showed a binding affinity of -5.8 kcal/mol between EVS and oleic acid, suggesting a stable substrate-lipase combination suitable for esterification.

Recent applications and future prospects of magnetic biocatalysts

Magnetic biocatalysts combine magnetic properties with the catalytic activity of enzymes, achieving easy recovery and reuse in biotechnological processes. Lipases immobilized by magnetic nanoparticles dominate. This review covers an advanced bibliometric analysis and an overview of the area, elucidating research advances. Using WoS, 34,949 publications were analyzed and refined to 450. The prominent journals, countries, institutions, and authors that published the most were identified. The most cited articles showed research hotspots. The analysis of the themes and keywords identified five clusters and showed that the main field of research is associated with obtaining biofuels derived from different types of sustainable vegetable oils. The overview of magnetic biocatalysts showed that these materials are also employed in biosensors, photothermal therapy, environmental remediation, and medical applications. The industry shows a significant interest, with the number of patents increasing. Future studies should focus on immobilizing new lipases in unique materials with magnetic profiles, aiming to improve the efficiency for various biotechnological applications.

Development and evaluation of an anti-candida cream based on silver nanoparticles

The ineffectiveness of azole drugs in treating Vulvovaginal Candidiasis (VVC) and Recurrent Vulvovaginal Candidiasis (RVVC) due to antifungal resistance of non-albicans Candida has led to the investigation of inorganic nanoparticles with biological activity. Silver nanoparticles (AgNPs) are important in nanomedicine and have been used in various products and technologies. This study aimed to develop a vaginal cream and assess its in vitro antimicrobial activity against Candida parapsilosis strains, specifically focusing on the synergy between AgNPs and miconazole. AgNPs were synthesized using glucose as a reducing agent and sodium dodecyl sulfate (SDS) as a stabilizer in varying amounts (0.50, 0.25, and 0.10 g). The AgNPs were characterized using UV-Visible (UV-Vis) and Fourier-Transform Infrared (FT-IR) spectroscopies, X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDX). Fifty strains of Candida parapsilosis were used to evaluate the synergistic activity. AgNPs synthesized with 0.5 g SDS had an average size of 77.58 nm and a zeta potential of -49.2 mV, while AgNPs with 0.25 g showed 91.22 nm and -47.2 mV, respectively. AgNPs stabilized with 0.1 g of SDS were not effective. When combined with miconazole, AgNPs exhibited significant antifungal activity, resulting in an average increase of 80% in inhibition zones. The cream developed in this study, containing half the miconazole concentration of commercially available medication, demonstrated larger inhibition zones compared to the commercial samples.

De novo design of bioactive phenol and chromone derivatives for inhibitors of Spike glycoprotein of SARS-CoV-2 in silico

This work presents the synthesis of 12 phenol and chromone derivatives, prepared by the analogs, and the possibility of conducting an in silico study of its derivatives as a therapeutic alternative to combat the SARS-CoV-2, pathogen responsible for COVID-19 pandemic, using its S-glycoprotein as a macromolecular target. After the initial screening for the ranking of the products, it was chosen which structure presented the best energy bond with the target. As a result, derivative 4 was submitted to a molecular growth study using artificial intelligence, where 8436 initial structures were obtained that passed through the interaction filters and similarity to the active glycoprotein pocket through the MolAICal computational package. Thus, 557 Hits with active configuration were generated, which is very promising compared to the BLA reference link for inhibiting the biological target. Molecular dynamics also simulated these compounds to verify their stability within the active protein site to seek new therapeutic propositions to fight against the pandemic. The Hit 48 and 250 are the most active compounds against SARS-CoV-2. In summary, the results show that the Hit 250 would be more active than the natural compound, which could be further developed for further testing against SARS-CoV-2. The study employs the de novo approach to design new drugs, combining artificial intelligence and molecular dynamics simulations to create efficient molecular structures. This research aims to contribute to the development of effective therapeutic strategies against the pandemic.

Antifungal Activity of Nanobiocomposite Films Based on Silver Nanoparticles Obtained Through Green Synthesis

The high incidence of Candida albicans infections has raised concerns regarding side effects and drug resistance, compounded by a limited number of alternative drugs. Silver nanoparticles (AgNPs) have prominent antimicrobial activity, but effective administration remains a challenge. In this study, AgNPs were synthesized via a green chemistry approach, using glucose as a reducing agent, and incorporated into an agar matrix to form a film (AgFilm). The AgNPs and AgFilm were characterized by Ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and atomic force microscopic (AFM). The UV-Vis spectra of the AgNPs and AgFilm showed bands at 415 and 413 nm, respectively. The PXRD and UV-Vis data suggest that the growth of AgNPs was effectively inhibited in the AgFilm. The diameter of AgNPs dispersed in AgFilm was 76 ± 42 nm, and the thickness of the film and 35 ± 3 µm. The antifungal activity of AgFilm was evaluated against 20 strains of C. albicans, demonstrating high antifungal activity with an inhibition zone of 19 ± 2 mm. Therefore, AgFilm could be a promising option for the treatment of superficial C. albicans infections.

Effect of TiO2 Microparticles in Lettuce (Lactuca sativa L.) Seeds and Seedlings

The particle size reduction technology is used in several segments, including sunscreens and new techniques and product improvement. One of the main particles used in the sunscreens formulation is titanium dioxide (TiO2). This formulation allows for better characteristics of these products. Perspectives like incorporation of the particles by other biological systems beyond humans and their effects should be observed. This work aimed to evaluate the titanium dioxide microparticles phytotoxicity on Lactuca sativa L. plants through tests of germination, growth, and weight analysis using microscopy techniques: optical microscopy (OM) and scanning electron microscopy (SEM). Some of the results showed cellular and morphological damage, mainly in the roots and 50 mg L-1 TiO2 concentration, confirmed by SEM. Additionally, anatomical damages like vascular bundle disruption and irregularity in the cortex cells were confirmed by SEM. Additionally, anatomical damages were observed on the three main organs (root, hypocotyl, and leaves) evidenced by the OM. Perspectives to confirm new hypotheses of the interaction of nanomaterials with biological systems are necessary.

Acute toxicity of titanium dioxide microparticles in Artemia sp. nauplii instar I and II

In this study, the toxicity effects of titanium dioxide (MTiO₂ ) microparticles on Artemia sp. nauplii instar I and II between 24 and 48 h was evaluated. The MTiO₂ were characterized using different microscopy techniques. MTiO₂ rutile was used in toxicity tests at concentration of 12.5, 25, 50, and 100 ppm. No toxicity was observed in Artemia sp. nauplii instar I at the time of 24 and 48 h. However, Artemia sp. nauplii instar II toxicity was observed within 48 h of exposure. MTiO₂ at concentrations of 25, 50 and 100 ppm was lethal for Artemia sp. with a significant difference (p ≤ .05) in relation to the control artificial sea water with LC₅₀ value at 50 ppm. Analysis of optical and scanning electron microscopy revealed tissue damage and morphological changes in Artemia sp. nauplii instar II. By using confocal laser scanning microscopy, cell damage was observed due to the toxicity of MTiO₂ at a concentration of 20, 50, and 100 ppm. The high mortality rate is related to the filtration of MTiO₂ by Artemia sp. nauplii instar II due to the complete development of the digestive tract.

Doped Carbon Quantum Dots/PVA Nanocomposite as a Platform to Sense Nitrite Ions in Meat

A sensor device based on doped-carbon quantum dots is proposed herein for detection of nitrite in meat products by fluorescence quenching. For the sensing platform, carbon quantum dots doped with boron and functionalized with nitrogen (B,N-Cdot) were synthesized with an excellent 44.3% quantum yield via a one-step hydrothermal route using citric acid, boric acid, and branched polyethylenimine as carbon, boron, and nitrogen sources, respectively. After investigation of their chemical structure and fluorescent properties, the B,N-Cdot at aqueous suspensions showed high selectivity for NO₂^- in a linear range from 20 to 50 mmol L^-1 under optimum conditions at pH 7.4 and a 340 nm excitation. Furthermore, the prepared B,N-Cdots successfully detected NO₂^- in a real meat sample with recovery of 91.4-104% within the analyzed range. In this manner, a B,N-Cdot/PVA nanocomposite film with blue emission under excitation at 360 nm was prepared, and a first assay detection of NO₂^- in meat products was tested using a smartphone application. The potential application of the newly developed sensing device containing a highly fluorescent probe should aid in the development of a rapid and inexpensive strategy for NO₂^- detection.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Ultrafast sonochemistry-based approach to coat TiO2 commercial particles for sunscreen formulation

TiO₂ is a common inorganic filter used in sunscreens due to its photoprotective effect on the skin against UV radiation. However, the use of this kind of material in cosmetics is limited by its inherent photocatalytic activity. It is known that coating on TiO₂ surface can improve some features. Although, many of the methodologies used for this purpose are still laborious and time-consuming. Thus, this work reports a novel, easy, cheap and fast strategy to coat TiO₂ particles by using a sonochemistry approach, aiming to decrease photocatalytic activity and to enhance colloidal stability. For this proposal, SiO₂, Al₂O₃, ZrO₂ and sodium polyacrylate (PAANa) were used to tune the surface of commercial TiO₂ particles and they were applied in a sunscreen formulation. The samples were characterized by XRPD, FT-IR, DLS, EDS, SEM and TEM. The photocatalytic activity and UV-shielding ability were also evaluated. The sunscreen formulations were prepared and characterized by zeta potential, DLS, and Sun Protection Factor (SPF). FT-IR, EDS, and charge surface of the particles confirmed the success of the sonochemistry coating. Additionally, TiO₂@Al₂O₃, TiO₂@SiO₂ and TiO₂@PAANa show a lower photocatalytic activity than original TiO₂ with similar UV-shielding ability. The sunscreens produced with the coated TiO₂ have similar SPF to the one with commercial TiO₂. Specifically, the sunscreen with TiO₂@PAANa shows an increase in colloidal stability. Herein, the incorporation of the sonochemical-coated TiO₂ particles in sunscreen formulations may produce sunscreens with better aesthetic appearance and a greater health security due to its lower free radicals production.

Remineralização de Lesões Iniciais de Cárie em Esmalte com Géis Contendo Nano- Hidroxiapatita

O objetivo do presente trabalho foi avaliar, in vitro, o potencial remineralizador de géis experimentais através de um modelo de indução de lesão de cárie inicial em esmalte. Foram utilizados incisivos bovinos cortados e aleatorizados em cinco grupos: GC  (gel sem flúor e sem nano-hidroxiapatita) GF (gel de flúor experimental) GN (gel de nano- hidroxiapatita) GNF (gel de nano- hidroxiapatita e flúor) GFC (gel de flúor comercial 1.23%). Os espécimes foram submetidos a um desafio cariogênico para indução química de lesão de cárie. Logo após, os géis foram aplicados e os espécimes foram submetidos a um modelo de ciclagem de     pH. A análise de microdureza Knoop foi realizada em três momentos: antes e após a indução de cárie e após a ciclagem de pH. A microdureza em corte longitudinal foi executada após o último dia de ciclagem de pH. Logo após, as amostras foram analisadas por microscopia eletrônica de varredura (MEV) e por espectroscopia de infravermelho com transformada de Fourier (FTIR). Não houve diferença estatisticamente significante entre os grupos experimentais (GF, GN, GNF, GFC) entretanto, foram encontradas diferenças entre estes e o grupo GC. Quanto à microdureza de corte longitudinal, os dados não mostraram diferenças entre os grupos. Pela análise de composição química por FTIR, não houve diferenças nas composições químicas das amostras avaliadas. A MEV revelou características superficiais distintas entre os grupos. Os géis foram eficazes na remineralização das lesões de cárie na superfície de esmalte, mas não em profundidade.Palavras-chave: Cárie Dentária. Nanopartículas. Flúor.

Avaliação Físico-Química e Microbiológica de uma Resina Ortodônica Associada com Nanoparticulos de Prata/Fosfato de Cálcio

O objetivo foi avaliar propriedades físico-químicas, resistência ao cisalhamento em esmalte bovino e efeito antibacteriano de uma resina ortodôntica (RO) (Orthocem, FGM) incorporada com nanopartículas de prata (AgNPs) com ou sem fosfato de cálcio (CaP). As RO foram preparadas com 1 ou 5% em peso de AgNPm ou de AgNP-CaP. Foram avaliados grau de conversão (GC), sorção (WS) e solubilidade (SO) em água, flexão de três pontos (resistência à flexão, FS e módulo, E), rugosidade superficial (Ra) e microdureza Knoop (KHN). A adesão ao esmalte bovino foi avaliada por ensaio de resistência ao cisalhamento (SBS) de bráquetes metálicos.  A atividade antimicrobiana da resina contra Streptococcus mutans foi medida por contagem de unidades formadoras de colônias (UFC). Os dados foram analisados estatisticamente por ANOVA e teste de Tukey (p<0,05). Os resultados mostraram que GC, FS, KHN, SBS e UFC não mostraram diferença estatística entre os grupos. O valor de WS diminuiu em RO com 1% de AgNP e o valor de SO também diminuiu em RO com 5% em peso de AgNP. RO com 5% de AgNP obteve maior FS que as outras resinas. RO com 1% e 5% de AgNP e 5% de AgNP-CaP atingiram uma rugosidade estatisticamente inferior a RO controle. A incorporação de AgNP em RO altera algumas propriedades físico-químicas, mas não interfere na sua adesão ao esmalte e polimerização. O uso de CaP associado ao AgNP pode induzir alterações menores nas propriedades físico-químicas do material.Palavras-chave: Resina Ortodôntica. Nanopartícula de Prata. Atividade Antimicrobiana.

Avaliação da Adesão, Sorção de Água e Solubilidade de Resinas Compostas Autoadesivas Experimentais para Capeamento Pulpar Direto

O objetivo foi analisar resinas compostas experimentais para capeamento pulpar direto em propriedades físico-químicas selecionadas, comparando com hidróxido de cálcio fotopolimerizável e MTA. Duas resinas compostas capeadoras foram preparadas, uma sem adição de partículas bioativas (controle) e a outra com 30% em peso (experimental) de nanopartículas de hidroxiapatita adsorvidas com sinvastatina (10%), com glutationa (10%) e de beta fosfato tricálcio (10%). Foram utilizados 36 terceiros molares hígidos extraídos, onde foi realizado preparo cavitário na região coronária até atingir a câmara pulpar para posterior restauração com um dos materiais. Os espécimes foram cortados em fatias (1mm) e essas foram submetidas ao teste de resistência de união ao push-out. Espécimes em forma de disco (n8) foram preparados e avaliados (ISO4049) quanto a sorção e solubilidade. A análise estatística  foi feita com ANOVA e teste de Tukey (a5%). Os resultados de resistência de união mostraram que o MTA e o hidróxido de cálcio apresentaram pior adesão do que as resinas, e os maiores valores foram obtidos com a resina experimental (p<0,05). Maior sorção de água foi observada com o hidróxido de cálcio e os demais materiais não apresentaram diferenças estatísticas. O hidróxido de cálcio obteve maior solubilidade que a resina controle e a experimental (p<0,05). Em conclusão, a resina experimental com partículas bioativas promove maior adesão à dentina e menor sorção e solubilidade que hidróxido de cálcio e MTA, esses materiais que são tradicionalmente usados para capeamento pulpar.Palavras-chave: Dental Pulp Capping. Simvastatin Calcium Hydroxide.

SILVER NANOPARTICLES-DISK DIFFUSION TEST AGAINST Escherichia coli ISOLATES

Nanotechnology can be a valuable ally in the treatment of infections. Silver nanoparticles (AgNPs) are structures that have antimicrobial activity. The aim of this study was to produce AgNPs by green methods, characterize these structures, and assess their antimicrobial activity against Escherichia coli associated with the antibiotic ciprofloxacin. AgNPs were characterized by spectroscopic and microscopic techniques. Antimicrobial activity was evaluated by the disk diffusion method against 10 strains of E. coli. The synthesized AgNPs showed a spherical shape and a size of 85.07 ± 12.86 nm (mean ± SD). AgNPs increased the activity of ciprofloxacin by 40% and may represent a new therapeutic option for the treatment of bacterial infections.

Antifungal activity of silver nanoparticles obtained by green synthesis

Silver nanoparticles (AgNPs) are metal structures at the nanoscale. AgNPs have exhibited antimicrobial activities against fungi and bacteria; however synthesis of AgNPs can generate toxic waste during the reaction process. Accordingly, new routes using non-toxic compounds have been researched. The proposal of the present study was to synthesize AgNPs using ribose as a reducing agent and sodium dodecyl sulfate (SDS) as a stabilizer. The antifungal activity of these particles against C. albicans and C. tropicalis was also evaluated. Stable nanoparticles 12.5 ± 4.9 nm (mean ± SD) in size were obtained, which showed high activity against Candida spp. and could represent an alternative for fungal infection treatment.

Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations

Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as "pau branco". Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The (13)C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d,p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.