Juan Antonio Zapien

Polystyrene nanoplastics (PS-NPs) are increasingly recognized as environmental contaminants with potential implications for human health. However, the changes that polystyrene undergoes under environmental conditions, as well as the cellular stress responses and adaptive processes induced by these particles in human neuronal cell models, have not yet been fully characterized. In this study, we investigated the effects of 100 nm polystyrene nanoplastics functionalized with carboxyl groups (PS-NPs-COOH) on SH-SY5Y cells after 24 h of exposure, focusing on cell viability, intracellular particle accumulation, oxidative stress, antioxidant responses, and endoplasmic reticulum (ER) stress-associated signaling. Cell viability decreased significantly (p < 0.0001) to 68% at a concentration of 500 µg/mL, compared to 96.14% in the control group. Holotomographic microscopy showed concentration-dependent intracellular accumulation and aggregation of PS-NPs-COOH. Exposure was also associated with increased dihydroethidium-derived fluorescence, consistent with an alteration in cellular oxidative status. The increased expression of NRF2 and antioxidant response-related genes suggested a compensatory transcriptional response to the oxidative stress generated. In parallel, changes in ER stress-associated markers, including components of the unfolded protein response (UPR), together with alterations in apoptosis-related transcripts, indicated the involvement of interconnected cellular stress response pathways. These responses varied according to the exposure concentration of PS-NPs-COOH, possibly suggesting an adaptive process in response to cellular stress. Further studies are needed to clarify this proposed adaptive response and determine the balance between cellular dysfunction and survival mechanisms.

As global plastic production and inadequate waste management continue to increase, fragmentation and weathering accelerate the widespread occurrence of micro- and nanoplastics (MNPs) across environmental compartments. In this context, advanced oxidation processes (AOPs), particularly electrochemical advanced oxidation processes (EAOPs), have emerged as promising strategies for addressing MNPs contamination due to the generation of reactive species capable of inducing polymer transformation. Their performance depends on numerous factors including polymer properties, treatment configuration, electrode material, current density, supporting electrolyte, additives, and hybrid enhancement strategies. To date, most studies have been conducted under simplified laboratory conditions using heterogeneous protocols. However, in actual environmental and wastewater matrices, radical scavengers and coexisting constituents can suppress oxidation and alter degradation pathways. Moreover, particle-size reduction and changes in surface chemistry are often interpreted as degradation without confirming mineralization, carbon balance, transformation-product fate, or reduced toxicity. While electrochemical, spectroscopic, and microscopic techniques provide complementary information for monitoring these transformations, harmonized analytical workflows remain insufficiently adopted. Based on this critical assessment, this review integrates advanced oxidation and electrochemical strategies for MNPs treatment and monitoring, focusing on degradation mechanisms, electrochemical detection, complementary characterization, transformation products, toxicity, real-matrix effects, and scale-up challenges.

We investigated the influence of gold deposition on the magnetic behavior, biocompatibility, and bioactivity of CoFe₂O₄ (MCF) nanomaterials (NMs) functionalized with sodium citrate (Cit) or glycine (Gly). The resulting multifunctional plasmonic nanostructured materials (MCF-Au-L, where L is Cit, Gly) exhibit superparamagnetic behavior with magnetic saturation of 59 emu/g, 55 emu/g, and 60 emu/g, and blocking temperatures of 259 K, 311 K, and 322 K for pristine MCF, MCF-Au-Gly, and MCF-Au-Cit, respectively. The MCF NMs exhibit a small uniform size (with a mean size of 7.1 nm) and an atomic ratio of Fe:Co (2:1). The gold nanoparticles (AuNPs) show high heterogeneity as determined by high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX). The UV-Vis spectroscopy of the composites reveals two localized surface plasmons (LSPs) at 530 nm and 705 nm, while Fourier Transformed-Infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirm the presence of Cit and Gly on their surface. Subsequent biocompatibility tests confirm that MCF-Au-L NMs do not exert hemolytic activity (hemolysis < 5%). In addition, the CCK-8 viability assay tests indicate the higher sensitivity of cancerous cells (A549) to the photoactivity of MCF-Au compared to healthy Detroit 548 (D548) cell lines. We use advanced microscopy techniques, namely atomic force, fluorescence, and holotomography microscopies (AFM, FM, and HTM, respectively) to provide further insights into the nature of the observed photoactivity of MCF-Au-L NMs. In addition, in situ radiation, using a modified HTM microscope with an IR laser accessory, demonstrates the photoactivity of the MCF-Au NMs and their suitability for destroying cancerous cells through photodynamic therapy. The combined imaging capabilities demonstrate clear morphological changes, NMs internalization, and oxidative damage. Our results confirm that the fabricated multifunctional NMs exhibit high stability in aqueous solution, chemical solidity, superparamagnetic behavior, and effective IR responses, making them promising precursors for hybrid cancer therapy.

Modern imaging strategies are paramount to studying living systems such as cells, bacteria, and fungi and their response to pathogens, toxicants, and nanomaterials (NMs) as modulated by exposure and environmental factors. The need to understand the processes and mechanisms of damage, healing, and cell survivability of living systems continues to motivate the development of alternative imaging strategies. Of particular interest is the use of label-free techniques (microscopy procedures that do not require sample staining) that minimize interference of biological processes by foreign marking substances and reduce intense light exposure and potential photo-toxicity effects. This review focuses on the synergic capabilities of atomic force microscopy (AFM) as a well-developed and robust imaging strategy with demonstrated applications to unravel intimate details in biomedical applications, with the label-free, fast, and enduring Holotomographic Microscopy (HTM) strategy. HTM is a technique that combines holography and tomography using a low intensity continuous illumination laser to investigate (quantitatively and non-invasively) cells, microorganisms, and thin tissue by generating three-dimensional (3D) images and monitoring in real-time inner morphological changes. We first review the operating principles that form the basis for the complementary details provided by these techniques regarding the surface and internal information provided by HTM and AFM, which are essential and complimentary for the development of several biomedical areas studying the interaction mechanisms of NMs with living organisms. First, AFM can provide superb resolution on surface morphology and biomechanical characterization. Second, the quantitative phase capabilities of HTM enable superb modeling and quantification of the volume, surface area, protein content, and mass density of the main components of cells and microorganisms, including the morphology of cells in microbiological systems. These capabilities result from directly quantifying refractive index changes without requiring fluorescent markers or chemicals. As such, HTM is ideal for long-term monitoring of living organisms in conditions close to their natural settings. We present a case-based review of the principal uses of both techniques and their essential contributions to nanomedicine and nanotoxicology (study of the harmful effects of NMs in living organisms), emphasizing cancer and infectious disease control. The synergic impact of the sequential use of these complementary strategies provides a clear drive for adopting these techniques as interdependent fundamental tools. Graphical abstract

Bare and doped zinc oxide nanomaterials (ZnO NMs) are of great interest as multifunctional platforms for biomedical applications. In this study, we systematically investigate the physicochemical properties of Aluminum doped ZnO (AZO) and its bio-interactions with neuroblastoma (SH-SY5Y) and red blood (RBCs) cells. We provide a comprehensive chemical and structural characterization of the NMs. We also evaluated the biocompatibility of AZO NMs using traditional toxicity assays and advanced microscopy techniques. The toxicity of AZO NMs towards SH-SY5Y cells, decreases as a function of Al doping but is higher than the toxicity of ZnO NMs. Our results show that N-acetyl cysteine protects SH-SY5Y cells against reactive oxygen species toxicity induced by AZO NMs. ZnO and AZO NMs do not exert hemolysis in human RBCs at the doses that cause toxicity (IC50) in neuroblastoma cells. The Atomic force microscopy qualitative analysis of the interaction of SH-SY5Y cells with AZO NMs shows evidence that the affinity of the materials with the cells results in morphology changes and diminished interactions between neighboring cells. The holotomographic microscopy analysis demonstrates NMs' internalization in SH-SY5Y cells, changes in their chemical composition, and the role of lipid droplets in the clearance of toxicants. Graphical Abstract

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn²⁺ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H₂O)₆]²⁺ to create Zn(H₂O)₃(ace)(BF₄)₂. The viscosity of 1ace‐1H₂O is 0.032 Pa s, significantly lower than that of 1ace‐0H₂O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm⁻¹) and shows lower freezing point of −45 °C, as opposed to 1ace‐0H₂O of 4.04 mS cm⁻¹ and 12 °C, respectively. The acidity of 1ace‐1H₂O is ≈2.8, higher than 0ace‐1H₂O at ≈0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO₃/ZnF₂‐rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm⁻², and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of ≈99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g⁻¹ at 5 A g⁻¹ at room temperature, and operated at −40 °C with a capacity of 66.8 mAh g⁻¹.

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn²⁺ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H₂O)₆]²⁺ to create Zn(H₂O)₃(ace)(BF₄)₂. The viscosity of 1ace‐1H₂O is 0.032 Pa s, significantly lower than that of 1ace‐0H₂O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm⁻¹) and shows lower freezing point of −45 °C, as opposed to 1ace‐0H₂O of 4.04 mS cm⁻¹ and 12 °C, respectively. The acidity of 1ace‐1H₂O is ≈2.8, higher than 0ace‐1H₂O at ≈0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO₃/ZnF₂‐rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm⁻², and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of ≈99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g⁻¹ at 5 A g⁻¹ at room temperature, and operated at −40 °C with a capacity of 66.8 mAh g⁻¹.

Optical sensors using zero‐reflection points (ZRPs) enable excellent sensitivity due to the accompanying phase singularities and the steepest slope of the reflectivity curve. Here, the collaborative manipulation of three ZRPs in a simple platform formed by a lithography‐free, metal‐dielectric‐metal structure with unsurpassed, experimentally demonstrated, limit of detection ≈2 × 10⁻⁸ refractive index unit is reported. The sensor relies on: i) strong coupling between p‐polarized surface plasmon polariton and photonic waveguide, leading to reflection suppression, Rabi splitting and phase singularities; ii) simultaneous implementation of two orthogonally polarized ZRPs, enabling spectral overlap of s‐polarized photonic modes (R_s) with the coupled p‐polarized resonances (R_p); and iii) ellipsometry‐based sensing where the s‐polarized ZRPs provide a stable reference to boost the sensor performance in terms of the amplitude ratio and phase difference of R_p and R_s thereby naturally forming a refinement measuring scale akin to a Vernier scale. Remarkably, the precise manipulation of ZRPs enables resetting the sensor to its optimal sensing point. The capability has been demonstrated for a biosensor of SARS‐CoV‐2 spike (S2) protein that can track the full functionalization process then reset to perform dose‐dependent detection of the S2 protein. This work provides a new strategy for the development of optical sensors and perfect light absorbers.