In cancer, the use of microbots based on anaerobic bacteria as specific transporters targeting tumor tissues has been explored since most solid tumors exhibit hypoxic regions. The aim of this study was to develop and characterize magnetic microbots based on Bifidobacteria and iron oxide fluorescent magnetic nanoparticles complexed with chitosan and a hypoxia inducible plasmid. In addition, the efficiency of the microbots for gene delivery to solid tumors was evaluated in an in vivo model by florescence and luminescence. To elaborate microbots, iron oxide fluorescent magnetic nanoparticles complexed with chitosan and a hypoxia-inducible plasmid called nanocomplex (NCs) with a size of 302 nm and a ζ potential of +16 mV were obtained and loaded onto Bifidobacteria membranes. Microbots with a diameter between 1–2 µm were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Microbots were injected intravenously through the tail vein to tumor-bearing mice, and then a magnet was placed to focus them to the tumor area. Forty-eight hours after injection, the biodistribution was determined by florescence and luminescence. The greatest luminescence and fluorescence emitted were found in tumor tissue compared with the normal organs. We created a vector that can be directed by a magnet and deliver genes whose expression is regulated by hypoxic microenvironment of tumor.

Acute respiratory diseases caused by viral pathogens such as Influenza A continue to represent a major global health challenge, emphasizing the need for rapid, sensitive, and accessible diagnostic tools. In this work, a carbon screen-printed electrode (SPCE)-based electrochemical immunosensor for the detection of an Influenza A (H1) antigen is reported, incorporating a comparative electrochemical evaluation of four electrode materials. Fe₃O₄ nanoparticles, Fe₃O₄@C nanoparticles, graphene quantum dots (GQDs), and gold nanoparticles (AuNPs) were systematically assessed by cyclic voltammetry to evaluate their electrocatalytic performance. The highest electrochemical response was selected for biosensor construction. The immunosensor was fabricated by immobilizing antibodies on a modified SPCE and characterized using differential pulse voltammetry (DPV). A concentration-dependent response was observed for H1 antigen concentrations ranging from 0 to 300 ng/mL, with a minimum detectable concentration (MDC) of 1 ng/mL and limit of detection (LOD) of 176 ng/mL and 45 ng/mL for serum and nasopharyngeal swabs, respectively. The biosensor performance was specifically evaluated in complex biological fluids, demonstrating reproducible performance and moderate selectivity against non-target influenza subtypes. Overall, this study highlights the critical role of electrode material selection in determining electrochemical immunosensor performance and supports the potential of SPCE-based platforms for the screening of an Influenza A (H1) antigen in point-of-care-oriented applications.