Biology subjects

Macia, J.

Publications and source records attributed to Macia, J..

4 recordsLinked to original sources

bioRxiv2026

Intracellular bio-synthesizing Gold Nanoparticles using bacterial systems and their applications in photothermal therapy (A green approach)

Background: Conventional cancer therapies are heavily constrained by systemic toxicity, off-target side effects, and poor deep-tissue penetration due to the highly heterogeneous tumor microenvironment (TME). Although gold nanoparticles (AuNPs) possess exceptional localized surface plasmon resonance (LSPR) properties ideal for photothermal therapy (PTT), their clinical translation is bottlenecked by inconsistent passive accumulation and chemical toxicity arising from conventional synthetic surfactants. Objective: This study developed a sustainable, biocompatible bio-hybrid platform utilizing the probiotic Escherichia coli Nissle 1917 (EcN) as an autonomous, tumor-homing living carrier integrated with AuNPs synthesized via an eco-friendly intracellular green chemistry approach. Methods: EcN cultures were prepared in Luria-Bertani (LB) medium and subsequently exposed to a 1 mM chloroauric acid (HAuCl4) metallic precursor. A facile, room-temperature green synthesis protocol was established by utilizing ascorbic acid (Vitamin C) as a non-toxic co-reductant to drive a seed-mediated crystallization onto intra-bacterial metallic seeds. The bio-hybrid system (EcN::AuNPs) was characterized via visual inspection, UV-Vis spectroscopy, and in vitro PTT assays under continuous-wave near-infrared (NIR) laser irradiation. Results: Visual confirmation showed an irreversible color shift from pale yellow to a deep dark-brownish hue, serving as a direct diagnostic indicator of successful Au3+ to Au0 reduction. UV-Vis spectroscopic analysis revealed a distinct, broadened surface plasmon resonance (SPR) band centered at 560nm, indicating the formation of stabilized, isotropic gold nanostructures (30-60nm) subjected to near-field electromagnetic coupling within the complex intracellular compartments (periplasm and cytoplasm). Biocompatibility assays demonstrated a significant collapse in cell viability from 10^8CFU/mL down to 10^3CFU/mL, driven by a combination of trivalent gold heavy-metal toxicity, mechanical disruption of the peptidoglycan wall from spatial confinement, and severe metabolic/oxidative stress. Nevertheless, the remaining surviving population maintained required active chemotactic capabilities, while the lysed bacterial matrix provided a natural protein capping layer that prevented nanoparticle aggregation. Under 5 minutes of continuous NIR laser irradiation, the EcN::AuNPs platform exhibited exceptional concentration-dependent hyperthermia kinetics, triggering a drastic thermal escalation from 20 C to an absolute peak of 75.4 C, vastly outperforming all baseline control groups (pure EcN, bare HAuCl4, and standalone ascorbic acid). Conclusion: The engineered EcN::AuNPs bio-hybrid platform represents a highly efficient and biosafe "bacteriobot" paradigm. By shifting the SPR footprint and leveraging the native bacterial cell envelope for colloidal stability, this system achieves an optimal equilibrium between active biological tumor targeting and rapid, localized photothermal ablation, offering a promising alternative for targeted oncological interventions.

synthetic biology↗

bioRxiv2024

CHARACTERIZATION OF RECOMBINASE ACTIVITY ACROSS CELLULAR GROWTH PHASES

Recombinases, which are enzymes that catalyze targeted DNA modifications, hold significant potential in synthetic biology. Their capacity to precisely manipulate genetic material enables the construction of complex genetic circuits that can be dynamically reconfigured in response to environmental stimuli. Such capabilities are essential for developing synthetic organisms tailored for specific functions, including biosensing, bioremediation, and pharmaceutical production. Therefore, characterizing the dynamics of recombinases is crucial for the innovative design of cellular devices. A deeper understanding of how recombinases interact with DNA in various conditions can improve the efficiency and control of genetic modifications, thereby enhancing both the functionality and reliability of synthetic biological systems. This study presents a detailed examination of the dynamics and efficiency of the serine recombinase Bxb1, focusing on its behavior under controlled expression in Escherichia coli. It highlights the significant influence of cellular growth phases (exponential and stationary) on the efficiency of recombinase-mediated gene expression. Our findings show that recombinase activity is maintained during stationary phase, which is critical to ensure ongoing recombination without the need for the continuous presence of an inducer. In experiments, we quantified the recombination efficiency of Bxb1 by monitoring expression of green fluorescent protein (GFP) as a reporter. Optimal expression of Bxb1, which maximized the recombination efficiency, occurred during exponential phase. However, once the culture reached stationary phase, accumulated Bxb1 continued to facilitate recombination, although GFP expression levels plateaued due to reduced cellular activity. These insights are relevant for synthetic biology applications where precise control of genetic functions is necessary.

synthetic biology↗

bioRxiv2024

Irregular light schedules induce alterations on daily rhythms and gene expression in mice

Synchronization of internal biological rhythms with external light-dark cycles is crucial for proper function and survival of the organisms, however modern life often imposes irregular light exposure, disrupting these internal clocks. This study investigated the effects of short-term shifted light-dark cycles on mice rhythmicity, and whether these alterations trigger molecular or behavioral changes. We evaluated locomotor activity, different behavioral domains and gene expression in the hypothalamus and medial prefrontal cortex. Despite non prominent behavioral impairments, such as anxiety or cognitive deficits, we observed a notable simplification in the locomotor activity patterns of the mice subjected to disrupted light-dark cycles. Molecular alterations included dysregulations in oscillations of core clock genes (Cry2, Per2) and disruptions in expression of genes involved in neuroplasticity, motivation, and stress responses, including GluA1, Crhr2, and Vip in both studied brain areas. Our study reveals that even brief light cycle shifts can disrupt circadian regulation at the molecular level, despite minimal behavioral changes. This molecular-behavioral discrepancy may suggest a complex adaptive response to drastic short-term light perturbations. Understanding the complex interplay between external light cues and internal biological rhythms regulation is crucial for mitigating the negative consequences of irregular light exposure on physiological processes and overall well-being.

neuroscience↗

bioRxiv2024

Lack of rhythmicity in Bmal1 deficient mice impairs motivation towards natural stimuli.

Maintaining appropriate circadian rhythmicity is essential for coordinating the activity of biological functions in mammalian organisms. A variety of physiological and behavioral changes have been associated with disturbances of this complex clock mechanism. In the present study, we delve into the consequences of circadian arrhythmia using the Bmal1-knockout (KO) mouse line aiming to explore potential behavioral and motivational implications. We were able to identify the intricate activity patterns that define circadian disturbance in Bmal1-KO mice by utilizing a new analysis model based on entropy divergence. Alterations in locomotor activity were accompanied by disruptions of circadian expression patterns in various clock genes as revealed by gene expression analysis. Additionally, we found a dysregulated gene expression profile in Bmal1-KO mice regarding genes related to circadian control in various brain nuclei. Specifically, the ventral striatum exhibited a dysregulation in the expression levels of genes modulating reward and motivation. Further investigation revealed that BMAL1 deficient mice showed a sustained rise in motivation and seeking behavior for food and water reinforcers in the self-administration paradigm, independently of the caloric content of the reward. Together, our data reveal that disruptions in circadian rhythmicity, induced by alterations in the molecular clock, also impact the gene expression regulating the reward system. This, in turn, can lead to altered seeking behavior and motivation for natural rewards. In summary, the present study contributes to our understanding of how reward processing is under the regulation of circadian clock machinery.

neuroscience↗