Micro, Volume 4, Issue 4 (December 2024) – 19 articles

The non-specific and minimally selective nature of traditional drug administration methods, along with various other limitations, makes the use of drug delivery systems more favorable. Light-responsive, or light-triggered, drug delivery systems provide more controlled and less invasive treatment approaches, addressing the shortcomings of traditional methods. In this paper, we reviewed studies utilizing light-triggered nanoparticles (NPs) for treating cancer and various other diseases, focusing on photodynamic therapy (PDT) and photothermal therapy (PTT) in both in vivo and in vitro applications. Most of the reviewed studies employed synergistic approaches that combined PDT or PTT with other therapeutic methods to leverage the strengths of both techniques and enhance treatment efficiency or to overcome the individual limitations of each method, which is discussed extensively in this paper. Full article

Various electrospinning techniques can be used to produce nanofiber mats with randomly oriented or aligned nanofibers made of different materials and material mixtures. Such nanofibers have a high specific surface area, making them sensitive as sensors for health monitoring. The entire nanofiber mats are very thin and lightweight and, therefore, can be easily integrated into wearables such as textile fabrics or even patches. Nanofibrous sensors can be used not only to analyze sweat but also to detect physical parameters such as ECG or heartbeat, movements, or environmental parameters such as temperature, humidity, etc., making them an interesting alternative to other wearables for continuous health monitoring. This paper provides an overview of various nanofibrous sensors made of different materials that are used in health monitoring. Both the advantages of electrospun nanofiber mats and their potential problems, such as inhomogeneities between different nanofiber mats or even within one electrospun specimen, are discussed. Full article

The colonization of historical buildings and monuments by fungi, algae, and bacteria is a common phenomenon. This often leads to deterioration processes that cause either visual or structural harm. The Batalha Monastery in Portugal, a UNESCO World Heritage Site, currently shows significant surface changes to the stone architectural elements within both the Founder’s Chapel and the church, including a widespread pink discoloration on the walls and columns. The main goal of this study was to analyze the biological colonization and assess the influence of bacterial communities on the biodeterioration of Ançã limestone, providing valuable insights to help conservators and restorers select the best preservation strategies for the monastery. The prokaryote population was characterized using both high-throughput DNA sequencing and culture-dependent methods and several orange-pink pigment-producing bacteria were identified, for example, Bacillus, Gordonia, Serratia and Methylobacterium, as well as Halalkalicoccus, an abundant archaeal genus. The pink discoloration observed could be due to biofilms created by bacteria that produce pigments, namely carotenoids. Biocolonization tests were performed using stone mock-ups, which were prepared and inoculated with the bacteria isolated in this study. These tests were designed to replicate the natural conditions of the monastery and monitor the colonization process to understand the discoloration phenomenon. Full article

In this work, we propose a strategy to optimize electrochemical hydrogen loading in magnesium–palladium thin films, using 5 M KOH as an electrolyte. Mg thin films of thickness 26 nm were deposited on sapphire (0001) substrates and capped by a 32 nm Pd layer. By performing cyclic voltammetry with in situ optical microscopy, it appears that a loading potential of at least −1.2 V vs. Hg/HgO has to be achieved at the sample’s surface to trigger magnesium hydride formation. Loading potential effects are then further explored by hydrogenography, where different hydride formation mechanisms appear based on the actual potential. With a larger loading potential of −1.6 V vs. Hg/HgO, a magnesium hydride blocking layer is formed; in this case, Pd hydride temporarily forms in the capping layer as hydrogen diffuses towards the magnesium layer. Loading is optimized for a lower potential of −1.2 V vs. Hg/HgO, which leads to larger hydride precipitates and delays the blocking layer formation; in this case, Pd hydride only appears after the magnesium layer is completely hydrided. Full article

The reinforcement of cast Cantor’s-type high-entropy alloys by MC carbides and their effect on the hot oxidation behavior were investigated. Three equimolar CoNiFeMnCr alloys without or with carbon and with either hafnium or tantalum were elaborated. Their as-cast microstructures were specified. Oxidation tests were carried out in air at 1100 °C. Flexural creep tests were performed at 1100 °C at 10 MPa. The carbide-free CoNiFeMnCr alloy was single-phased. The version with Hf and C added and the one with Ta and C added contained interdendritic eutectic script HfC and TaC carbides, respectively. After oxidation for 50 h at 1100 °C, all alloys were covered by a (Cr,Mn)₂O₃ scale with various proportions of Cr and Mn. HfO₂ or CrTaO₄ also formed. Oxidation resulted in a deep depletion in Cr and in Mn in the subsurface. Oxidation is much faster for the three alloys by comparison with chromia-forming alloys. Their bad oxidation behavior is obviously due to Mn and protection by coating is to be considered. The creep deformation of the carbide-free CoNiFeMnCr alloy was very fast. The creep resistance of the two versions reinforced by either HfC or TaC deformed much slower. The addition of these MC carbides led to a deformation rate divided by five to ten times. Now, creep behavior comparisons with commercial alloys are to be conducted. They will be performed soon. Full article

Mycoplasma infections pose significant challenges in the poultry industry, necessitating effective therapeutic interventions. Tiamulin, a veterinary antibiotic, has demonstrated efficacy against Mycoplasma species. However, the emergence of resistant Mycoplasma species could dramatically reduce the therapeutic potential, contributing to economic losses. Optimizing the tiamulin’s pharmacokinetic profile via nanocarrier incorporation could enhance its therapeutic potential and reduce the administration frequency, ultimately reducing the resistant strain emergence. Niosomes, a type of self-assembled non-ionic surfactant-based nanocarrier, have emerged as a promising drug delivery system, offering improved drug stability, sustained release, and enhanced bioavailability. In this study, niosomal nanocarriers encapsulating tiamulin were prepared, characterized and assessed in Mycoplasma-inoculated broilers following oral administration. Differential scanning colorimetry (DSC) confirmed the alterations in the crystalline state following components integration into the self-assembled structures formed during the formulation procedure. Transmission electron microscopy (TEM) showed the spherical nanostructure of the formed niosomes. The formulated nanocarriers exhibited a zeta potential and average hydrodynamic diameter of −10.65 ± 1.37 mV and 339.67 ± 30.88 nm, respectively. Assessment of the pharmacokinetic parameters following oral administration to Mycoplasma gallisepticum-infected broilers revealed the ability of the niosomal nanocarriers to increase the tiamulin’s bioavailability and systemic exposure, marked by significantly higher area under the curve (AUC) (p < 0.01) and prolonged elimination half-life (T_1/2) (p < 0.05). Enhanced bioavailability and prolonged residence time are crucial factors in maintaining therapeutic concentrations at reduced doses and administration frequencies. This approach provides a viable strategy to decrease the risk of subtherapeutic levels, thereby mitigating the development of antibiotic resistance. The findings presented herein offer a sustainable approach for the efficient use of antibiotics in veterinary medicine. Full article

Developing new nanomaterials and performing functionalization to increase their photocatalytic capacity are essential in developing low-cost, eco-friendly, and multipurpose-capacity catalysts. In this research, SnO₂/Se-doped quantum dots (QDs) covered with glycerol (SnO₂/Se-GLY) were synthesized using microwave irradiation. Then, their cover was replaced with glutaraldehyde through a ligand exchange procedure (SnO₂/Se-GLUT). The XRD analyses confirmed a tetragonal rutile structure of SnO₂. The HR-TEM analysis confirmed the generation of QDs with a size around 8 nm, and the optical analysis evidenced low bandgap energies of 3.25 and 3.26 eV for the SnO₂/Se-GLY and SnO₂/Se-GLUT QDs, respectively. Zeta-sizer analysis showed that the hydrodynamic sizes for both nanoparticles were around 230 nm (50 mg/L), and the zeta potential confirmed that SnO₂/Se-GLUT QDs were more stable than SnO₂/Se-GLY QDs. The cover-modified QDs (SnO₂/Se-GLUT) showed a higher and faster adsorption capacity, followed by a slower photocatalytic process than the original QDs (SnO₂/Se-GLY). The QTOF-LC-MS analysis confirmed MB degradation through the identification of intermediates such as azure A, azure B, azure C, and phenothiazine. Adsorption isotherm analysis indicated Langmuir model compliance, supporting the high monolayer adsorption capacity and efficiency of these QDs as adsorbent/photocatalytic agents for organic pollutant removal. This dual capability for adsorption and photodegradation, along with the demonstrated reusability, highlights the potential of SnO₂/Se QDs in wastewater treatment and environmental remediation. Full article

The search for new synthesis methodologies based on the principles of green chemistry has led to various studies for the production of silver nanoparticles (AgNPs) using extracts from different parts of plants. Based on this, the present study aims to carry out green synthesis (biosynthesis), characterization, and antibacterial evaluation of reduced and stabilized silver nanoparticles (AgNPs) with aqueous extracts of Minthostachys acris in a simple, ecological, and environmentally safe manner. The extraction process of the organic components is performed using two methods: immersion and the agitation of the leaves of Minthostachys acris Schmidt Lebuhn (Muña) at 0.1% for different times (0.5, 1, 3, 6, and 10 min). Compounds such as hydroxycinnamic acid derivatives, quinic, caffeic, rosmarinic acids, and flavonols present in the Muña extract facilitate the formation of AgNPs; this compounds act as a coating and stabilizing agent. The bioactive components from natural resources facilitate the formation of AgNPs, partially or completely replacing the contaminating and toxic elements present in chemical reagents. The biosynthesis is carried out at room temperature for pH 7 and 8. The synthesized AgNPs are characterized by UV-visible spectroscopy to identify the surface plasmon resonance (SPR) band, which shows an absorption peak around 419 nm and 423 nm for pH 7 and p.H 8, respectively, and Fourier-transform infrared spectroscopy (FTIR) to identify the possible biomolecules responsible for bioreduction and stabilization, with a peak at 1634 cm⁻¹. Dynamic light scattering (DLS) shows the hydrodynamic size of the colloidal nanoparticles between 11 and 200 nm, and scanning electron microscopy (SEM) reveals monodisperse AgNPs of different morphologies, mostly nanospheres, while Laser-Induced Breakdown Spectroscopy (LIBS) demonstrates the presence of Ag in the colloidal solution. The evaluation of the bactericidal activity of the AgNPs using the disk diffusion method against Escherichia coli (E. coli) and Staphylococus aureus (S.aureus) shows that the synthesized AgNPs have effective antibacterial activity against E. coli for the extracts obtained at 6 min for both the immersion and agitation methods, respectively. The significance of this work lies in the use of bioactive components from plants to obtain AgNPs in a simple, rapid, and economical way, with potential applications in biomedical fields. Full article

Micro/nanorobotics is becoming part of the future of medicine. One of the most efficient approaches to the construction of small medical robots is to base them on unicellular organisms. This approach inherently allows for obtaining complex capabilities, such as motility or environmental resistance. Single-celled organisms usually live in groups and are known to interact in many ways (matter, energy, and information), paving the way for potentially beneficial emergent effects. One such naturally expected effect is an increase in the sustainability of a population as a result of a more even redistribution of energy within the population. Our in silico experiments show that under harsh conditions, such as resource scarcity and a rapidly changing environment, altruistic energy exchange (supplying energy to weaker agents) can indeed markedly increase the sustainability of model bacteriabot groups, potentially increasing the efficiency of treatment. Although our work is limited exclusively to the development and use of a phenomenological computer model, we consider our results to be an important argument in favor of practical efforts aimed at implementing altruistic energy exchange strategies in real swarms of single-cell medical robots. Full article

Compacted graphite iron (CGI) attracts significant attention in the automotive industry thanks to its suitable thermomechanical properties and cost-effectiveness. A primary fracture mechanism at the microscale for CGI involves interfacial damage and debonding between graphite inclusions and its metallic matrix, which can occur under high-temperature service conditions due to a mismatch in the coefficients of thermal expansion between these two phases. Such microscopic interfacial damage can initiate macroscopic fractures in cast-iron components subjected to thermal loading. While this phenomenon was studied in various composites, there remains a lack of detailed information for CGI, especially related to the complex morphology of its graphite inclusions. This study investigates the influence of graphite morphology and type of matrix on the thermomechanical performance of CGI at high temperatures. A set of three-dimensional finite-element models were developed in the form of unit cells with a single graphite inclusion embedded within a cubic domain of the metallic matrix. Elastoplastic behaviour was assumed for both phases in the numerical simulations. The study is focused on the response of the constituents in CGI to pure thermal loading in order to explore the relationship between graphite morphology and fracture mechanisms. The findings aim to enhance understanding of how graphite morphology affects the behaviours of CGI under high-temperature conditions. Full article

Carbon dots (C-Dots) have garnered significant attention in various fields, including biomedical applications, photocatalysis, sensing, and optoelectronics, due to their high luminescence, biocompatibility, and ease of functionalization. However, concerns regarding their potential toxicity persist. Conventional synthesis methods for C-Dots often require long reaction times, high pressures, expensive equipment, extreme temperatures, and toxic reagents. In contrast, microwave irradiation provides a rapid, cost-effective, and scalable alternative for the synthesis of high-quality C-Dots. In this study, we report the single-step, 3-min synthesis of water-stable carbon dots at 100 °C, 120 °C, and 140 °C using microwave irradiation. Particle stability was achieved through polyethyleneimine (PEI) functionalization. The toxicity of the synthesized carbon dots was evaluated in marine crustaceans, revealing that C-Dots with an estimated size below 10 nm did not exhibit toxicity after 24 and 48 h of exposure. These findings demonstrate the potential of microwave-synthesized carbon dots as non-toxic, water-stable nanomaterials for environmental and biomedical applications. Full article

Aluminium and its composites are widely used in production to enhance the strength of lightweight objects. In this study, an AA7075/SiC composite was fabricated using a stir casting route. Multi-objective optimization and finite element analysis were performed with various process parameters on a manufactured aluminium composite (AA7075 + SiC) undergoing a laser beam welding process. Four welding parameters, i.e., pulse frequency, power, welding speed (transverse), and wire size were taken for laser welding as per the L-9 orthogonal array for experimental study. Tensile strength, deflection, temperature distribution, Rockwell hardness (fusion zone), and Rockwell hardness (heat affected zone) were taken as output parameters after welding. The standard deviation objective weighting–grey relational optimization method optimized the process parameter. ANSYS APDL 23 software was utilized to simulate the entire laser welding method with a cylindrical heat source to predict the temperature distribution in the butt-welded plates. This software uses finite element analysis and gives a deviation of only 5.85% for temperature distribution with experimental results. This study helps to understand the effect of various parameters on the welding strength of the aluminium composite. Full article

Bio-pigments are the colored primary and secondary metabolites released by microbes under stress conditions and are crucial for adaptation. Bio-pigments are being widely accepted for industrial utilization due to their natural form, organic source, and biodegradability. Also, the ease of cultivation, scalability and cost-effectiveness in terms of pigment extraction is bringing bio-pigments into the limelight. Chemical dyes are carcinogenic and pose a serious threat to human lives, which is another issue that environmentalists must address. However, bacterial pigments are safe to employ; therefore, the food, pharmaceutical, textile, and cosmetics sectors may all benefit from their applications. The therapeutic nature of bacterial pigments is revealed because of their antimicrobial, anticancer, cytotoxic, and remarkable antioxidant properties. Bio-pigments also have multifaceted properties and thus can be an attractive source for the next generation to live a sustainable life. The present review discusses the importance of bacterial pigments over synthetic dyes and their therapeutic and industrial potential. Extensive literature has been reviewed on the biomedical application of bacterial pigments, and further opportunities and future challenges have been discussed. Full article

This study investigated the development of Pullulan/Collagen nanofiber scaffolds integrated with mesenchymal stem cells (MSCs) to enhance chronic wound healing. The combination of these biopolymers aims to optimize the scaffold properties for cell growth, viability, and tissue regeneration. Materials and Methods: Pullulan, Collagen, and Pullulan/Collagen composite nanofibers were fabricated using electrospinning. The fibers were characterized using scanning electron microscopy (SEM) to determine the fiber diameter, and Fourier-transform infrared spectroscopy (FTIR) was employed to assess the molecular interactions. Cell viability was evaluated using MSCs cultured on the scaffolds and apoptosis assays were conducted to assess cell health. Distilled water was used as the solvent to maximize biocompatibility. Results: SEM analysis revealed that Pullulan nanofibers exhibited a larger average diameter (274 ± 20 nm) compared to Collagen fibers (167.03 ± 40.04 nm), while the Pullulan/Collagen composite fibers averaged 280 ± 102 nm. FTIR confirmed the molecular interactions between Pullulan and Collagen. Regarding biocompatibility, the Pullulan/Collagen scaffold demonstrated superior cell viability at 99% compared to 91% for Pullulan alone. Apoptosis assays indicated significantly lower necrosis rates for the composite scaffold (1.29%) than for the Pullulan-only scaffolds (2.35%). Conclusion: The use of distilled water as a solvent played a critical role in increasing cell viability and facilitating healthy proliferation of MSCs without cellular damage. Additionally, the reduced platelet activation and macrophage activity (0.75-fold for both) further supported the biocompatibility of the Pullulan/Collagen scaffold, demonstrating its potential for tissue engineering and chronic wound healing applications. Full article

The small dimensions of microfluidic channels allow for fast diffusive or passive mixing, which is beneficial for time-sensitive applications such as chemical reactions, biological assays, and the transport of to-be-detected species to sensors. In microfluidics, the need for fast mixing within milliseconds arises primarily because these devices are often used in fields where rapid and efficient mixing significantly impacts the performance and outcome of the processes. Active mixing with acoustics in microfluidic devices involves using acoustic waves to enhance the mixing of fluids within microchannels. Using sharp corners and wall patterns in acoustofluidic devices significantly enhances the mixing by acoustic streaming around these features. The streaming patterns around the sharp edges are particularly effective for the mixing because they can produce strong lateral flows that rapidly homogenize liquids. This work presents extensive characterizations of the effect of sharp-edged structures on acoustic mixing in bulk acoustic wave (BAW) mode in a silicon microdevice. The effect of side wall patterns in different angles and shapes, their positions, the type of piezoelectric transducer, and its amplitude and frequency have been studied. Following the patterning of the channel walls, a mixing time of 25 times faster was reached, compared to channels with smooth side walls exhibiting conventional BAW behavior. The average locally determined acoustic streaming velocity inside the channel becomes 14 times faster if sharp corners of 10° are added to the wall. Full article

In this paper, the impact of Lorentz forces and temperature on the natural frequencies of a piezoresistive sensor composed of two microcantilevers with integrated U-shaped thin-film aluminum heaters are investigated. Two types of experiments were performed. In the first, the sensor was placed in a magnetic field so that the current flowing in the heater, in addition to raising the temperature, produced Lorentz forces, inducing normal stresses in the plane of one of the microcantilevers. In the second, which were conducted without magnetic fields, only the temperature variation of the natural frequency was left. In processing of the results, the thermal variations were subtracted from the variations due to both Lorentz forces and temperature in the natural frequency, resulting in the influence of the Lorentz forces only. Theoretical relations for the Lorentz frequency offsets were derived. An indirect method of estimating the natural frequency of one of the cantilevers, through a particular cusp point in the amplitude–frequency response of the sensor, was used in the investigations. The findings show that for thin microcantilevers with silicon masses on the order of 4 × 10⁻⁷ g and currents of 25 µA, thermal eigenfrequency variations are dominant. The results may have applications in the design of similar microsensors with vibrational action. Full article

The unique structural properties of porous ceramics, such as low thermal conductivity, high surface area, controlled permeability, and low density, make this material valuable for a wide range of applications. Its uses include insulation, catalyst carriers, filters, bio-scaffolds for tissue engineering, and composite manufacturing. However, existing processing methods for porous ceramics, namely replica techniques and sacrificial templates, are complex, release harmful gases, have limited microstructure control, and are expensive. In contrast, the direct foaming method offers a simple and cost-effective approach. By modifying the surface chemistry of ceramic particles in a colloidal suspension, the hydrophilic particles are transformed into hydrophobic ones using surfactants. This method produces porous ceramics with interconnected pores, creating a hierarchical structure that is suitable for applications like nano-filters. This review emphasizes the importance of interconnected porosity in developing advanced ceramic materials with tailored properties for various applications. Interconnected pores play a vital role in facilitating mass transport, improving mechanical properties, and enabling fluid or gas infiltration. This level of porosity control allows for the customization of ceramic materials for specific purposes, including filtration, catalysis, energy storage, and biomaterials. Full article

The global rise in diabetes has highlighted the urgent need for continuous, non-invasive health monitoring solutions. Traditional glucose monitoring methods, which are invasive and often inconvenient, have created a demand for alternative technologies that can offer comfort, accuracy, and real-time data. In this study, the development of a textile-based organic electrochemical transistor (OECT) is presented, designed for non-invasive glucose sensing, aiming to integrate this technology seamlessly into everyday clothing. The document details the design, optimization, and testing of a one-component textile-based OECT, featuring a porous PEDOT:PSS structure and a glucose oxidase-modified electrolyte for effective glucose detection in sweat. The research demonstrates the feasibility of using this textile-based OECT for non-invasive glucose monitoring, with enhanced sensitivity and specificity achieved through the integration of glucose oxidase within the electrolyte and the innovative porous PEDOT:PSS design. These findings suggest a significant advancement in wearable health monitoring technologies, providing a promising pathway for the development of smart textiles capable of non-invasively tracking glucose levels. Future work should focus on refining this technology for clinical use, including individual calibration for accurate blood glucose correlation and its integration into commercially available smart textiles. Full article