Iron oxide nanoparticles: a platform for biomolecule conjugation

Among the nanomaterials, of great interest are iron oxide nanoparticles (IONPs), which possess unique magnetic properties, low toxicity and high biocompatibility. For these reason, IONPs are widely used in industrial and biomedical field. Here, IONPs were synthetized via co-precipitation method, obtaining NPs reproducible in shape and size distribution. First, IONPs were used as a platform for the conjugation of two thermophilic enzymes, L-aspartate oxidase and amylase to obtain an effective biocatalyst. Different binding strategies were studied leading to different enzymatic activity due to the different orientations and stretching of the proteins. Next, the NP-enzyme systems were nanoactuated by an alternate magnetic field (AMF) without increasing the overall temperature of the solution. Remarkably, the nano-systems were successfully reused for at three consecutive cycles of AMF with the loss of the 40% of the initial activity. IONPs were also used developed a nano-antibiotic system, using teicoplanin. The antimicrobial efficacy of NP-TEICO was assessed through classical microbiological methods and morphological studies. Results indicate that teicoplanin conjugation confers high and prolonged antimicrobial activity to IONPs toward Gram-positive bacteria, inhibiting also S. aureus biofilm formation, while no antimicrobial activity was detectable towards Gramnegative. Additionally, conjugation of teicoplanin improved the cytocompatibility of IONPs towards two human cell lines. To conclude, IONPs were successfully synthetized, functionalized and employed as a platform for biomolecules conjugation. Indeed two effective different nano-biocatalysts and a nano-antibiotic were obtained

Iron oxide nanoparticles: a platform for biomolecule conjugation

Among the nanomaterials, of great interest are iron oxide nanoparticles (IONPs), which possess unique magnetic properties, low toxicity and high biocompatibility. For these reason, IONPs are widely used in industrial and biomedical field. Here, IONPs were synthetized via co-precipitation method, obtaining NPs reproducible in shape and size distribution. First, IONPs were used as a platform for the conjugation of two thermophilic enzymes, L-aspartate oxidase and amylase to obtain an effective biocatalyst. Different binding strategies were studied leading to different enzymatic activity due to the different orientations and stretching of the proteins. Next, the NP-enzyme systems were nanoactuated by an alternate magnetic field (AMF) without increasing the overall temperature of the solution. Remarkably, the nano-systems were successfully reused for at three consecutive cycles of AMF with the loss of the 40% of the initial activity. IONPs were also used developed a nano-antibiotic system, using teicoplanin. The antimicrobial efficacy of NP-TEICO was assessed through classical microbiological methods and morphological studies. Results indicate that teicoplanin conjugation confers high and prolonged antimicrobial activity to IONPs toward Gram-positive bacteria, inhibiting also S. aureus biofilm formation, while no antimicrobial activity was detectable towards Gramnegative. Additionally, conjugation of teicoplanin improved the cytocompatibility of IONPs towards two human cell lines. To conclude, IONPs were successfully synthetized, functionalized and employed as a platform for biomolecules conjugation. Indeed two effective different nano-biocatalysts and a nano-antibiotic were obtained

Energy Transfer from Magnetic Iron Oxide Nanoparticles: Implications for Magnetic Hyperthermia

Magnetic iron oxide nanoparticles (IONPs) have gained momentum in the field of biomedical applications. They can be remotely heated via alternating magnetic fields, and such heat can be transferred from the IONPs to the local environment. However, the microscopic mechanism of heat transfer is still debated. By X-ray total scattering experiments and first-principles simulations, we show how such heat transfer can occur. After establishing structural and microstructural properties of the maghemite phase of the IONPs, we built a maghemite model functionalized with aminoalkoxysilane, a molecule used to anchor (bio)molecules to oxide surfaces. By a linear response theory approach, we reveal that a resonance mechanism is responsible for the heat transfer from the IONPs to the surroundings. Heat transfer occurs not only via covalent linkages with the IONP but also through the solvent hydrogen-bond network. This result may pave the way to exploit the directional control of the heat flow from the IONPs to the anchored molecules─i.e., antibiotics, therapeutics, and enzymes─for their activation or release in a broader range of medical and industrial applications

Antimicrobial activity of nanoconjugated glycopeptide antibiotics and their effect on Staphylococcus aureus biofilm

In the era of antimicrobial resistance, the use of nanoconjugated antibiotics is regarded as a promising approach for preventing and fighting infections caused by resistant bacteria, including those exacerbated by the formation of difficult-to-treat bacterial biofilms. Thanks to their biocompatibility and magnetic properties, iron oxide nanoparticles (IONPs) are particularly attractive as antibiotic carriers for the targeting therapy. IONPs can direct conjugated antibiotics to infection sites by the use of an external magnet, facilitating tissue penetration and disturbing biofilm formation. As a consequence of antibiotic localization, a decrease in its administration dosage might be possible, reducing the side effects to non-targeted organs and the risk of antibiotic resistance spread in the commensal microbiota. Here, we prepared nanoformulations of the ‘last-resort’ glycopeptides teicoplanin and vancomycin by conjugating them to IONPs via surface functionalization with (3-aminopropyl) triethoxysilane (APTES). These superparamagnetic NP-TEICO and NP-VANCO were chemically stable and NP-TEICO (better than NP-VANCO) conserved the typical spectrum of antimicrobial activity of glycopeptide antibiotics, being effective against a panel of staphylococci and enterococci, including clinical isolates and resistant strains. By a combination of different methodological approaches, we proved that NP-TEICO and, although to a lesser extent, NP-VANCO were effective in reducing biofilm formation by three methicillin-sensitive or resistant Staphylococcus aureus strains. Moreover, when attracted and concentrated by the action of an external magnet, NP-TEICO exerted a localized inhibitory effect on S. aureus biofilm formation at low antibiotic concentration. Finally, we proved that the conjugation of glycopeptide antibiotics to IONPs reduced their intrinsic cytotoxicity toward a human cell line

Human platelet lysate stimulates neurotrophic properties of human adipose-derived stem cells better than Schwann cell-like cells

Background: Trauma-associated peripheral nerve injury is a widespread clinical problem causing sensory and motor disabilities. Schwann cells (SCs) contribute to nerve regeneration, mainly by secreting nerve growth factor (NGF) and brain-derived neurotrophic factor. In the last years, adipose-derived stem cells (ASCs) differentiated into SCs (SC-ASCs) were considered as promising cell therapy. However, the cell trans-differentiation process has not been effectively showed and presents several drawbacks, thus an alternative approach for increasing ASCs neurotrophic properties is highly demanded. In the context of human cell-based therapies, Good Manufacturing Practice directions indicate that FBS should be substituted with a xenogeneic-free supplement, such as Human Platelet Lysate (HPL). Previously, we demonstrated that neurotrophic properties of HPL-cultured ASCs were superior compared to undifferentiated FBS-cultured ASCs. Therefore, as following step, here we compared the neurotrophic properties of differentiated SC-like ASCs and HPL-cultured ASCs.Methods: Both cell groups were investigated for gene expression level of neurotrophic factors, their receptors and neuronal markers. Moreover, the expression of nestin was quantitatively evaluated by flow cytometry. The commitment toward the SC phenotype was assessed with immunofluorescence pictures. Proteomics analysis was performed on both cells and their conditioned media to compare the differential protein profile. Finally, neurotrophic abilities of both groups were evaluated with a functional co-culture assay, assessing dorsal root ganglia survival and neurite outgrowth.Results: HPL-cultured ASCs demonstrated higher gene expression of NGF and lower expression of S100B. Moreover, nestin was present in almost all HPL-cultured ASCs and only in one quarter of SC-ASCs. Immunofluorescence confirmed that S100B was not present in HPL-cultured ASCs. Proteomics analysis validated the higher expression of nestin and the increase in cytoskeletal and ECM proteins involved in neural regeneration processes. The co-culture assay highlighted that neurite outgrowth was higher in the presence of HPL-ASCs or their conditioned medium compared to SC-ASCs.Conclusions: All together, our results show that HPL-ASCs were more neurotrophic than SC-ASCs. We highlighted that the HPL triggers an immature neuro-induction state of ASCs, while keeping their stem properties, paving the way for innovative therapies for nerve regeneration. Graphical Abstrac

High-dose exposure to polymer-coated iron oxide nanoparticles elicits autophagy-dependent ferroptosis in susceptible cancer cells

Ferroptosis, a form of iron-dependent, lipid peroxidation-driven cell death, has been extensively investigated in recent years, and several studies have suggested that the ferroptosis-inducing properties of iron-containing nanomaterials could be harnessed for cancer treatment. Here we evaluated the potential cytotoxicity of iron oxide nanoparticles, with and without cobalt functionalization (Fe2O3 and Fe2O3@Co-PEG), using an established, ferroptosis-sensitive fibrosarcoma cell line (HT1080) and a normal fibroblast cell line (BJ). In addition, we evaluated poly (ethylene glycol) (PEG)-poly(lactic-co-glycolic acid) (PLGA)-coated iron oxide nanoparticles (Fe3O4-PEG-PLGA). Our results showed that all the nanoparticles tested were essentially non-cytotoxic at concentrations up to 100 μg/mL. However, when the cells were exposed to higher concentrations (200–400 μg/mL), cell death with features of ferroptosis was observed, and this was more pronounced for the Co-functionalized nanoparticles. Furthermore, evidence was provided that the cell death triggered by the nanoparticles was autophagy-dependent. Taken together, the exposure to high concentrations of polymer-coated iron oxide nanoparticles triggers ferroptosis in susceptible human cancer cells

From monomeric to multimeric His-tag proteins conjugation to magnetic nanoparticles through NTA-Me2+: shape and size effects

Resumen del póster presentado a la 4th Spanish Conference on Biomedical Applications of Nanomaterials, celebrda online del 2 al 4 de junio de 2021.Peer reviewe

Evaluation of virological response and resistance profile in HIV-1 infected patients starting a first-line integrase inhibitor-based regimen in clinical settings

Background: Virological response and resistance profile were evaluated in drug-naïve patients starting their first-line integrase inhibitors (INIs)-based regimen in a clinical setting. Study design: Virological success (VS) and virological rebound (VR) after therapy start were assessed by survival analyses. Drug-resistance was evaluated at baseline and at virological failure. Results: Among 798 patients analysed, 38.6 %, 27.1 % and 34.3 % received raltegravir, elvitegravir and dolutegravir, respectively. Baseline resistance to NRTIs, NNRTIs, PIs and INIs was: 3.9 %, 13.9 %, 1.6 % and 0.5 %, respectively. Overall, by 12 months of treatment, the probability of VS was 95 %, while the probability of VR by 36 months after VS was 13.1 %. No significant differences in the virological response were found according to the INI used. The higher pre-therapy viremia strata was (<100,000 vs. 100,000-500,000 vs. > 500,000 copies/mL), lower was the probability of VS (96.0 % vs. 95.2 % vs. 91.1 %, respectively, P < 0.001), and higher the probability of VR (10.2 % vs. 15.8 % vs. 16.6 %, respectively, P = 0.010). CD4 cell count <200 cell/mm3 was associated with the lowest probability of VS (91.5 %, P < 0.001) and the highest probability of VR (20.7 %, P = 0.008) compared to higher CD4 levels. Multivariable Cox-regression confirmed the negative role of high pre-therapy viremia and low CD4 cell count on VS, but not on VR. Forty-three (5.3 %) patients experienced VF (raltegravir: 30; elvitegravir: 9; dolutegravir: 4). Patients failing dolutegravir did not harbor any resistance mutation either in integrase or reverse transcriptase. Conclusions: Our findings confirm that patients receiving an INI-based first-line regimen achieve and maintain very high rates of VS in clinical practice

Conjugating his-tagged proteins to magnetic nanoparticles: tips and challenges

Resumen del póster presentado al 5th Multistep Enzyme Catalyzed Processes Congress (MECPC), celebrado online del 13 al 16 de septiembre de 2021.The histidine tag (His-tag) is one of the most used affinity-tag for protein purification due to its small size and versatility. Agarose and sepharose beads containing nitriloacetic acid (NTA) transition metal derivatives are widely used for the purification of His-tagged proteins, thanks to their high affinity to the His-tag genetically fused to the protein of interest [1]. The same chemistry can be used to conjugate enzymes to magnetic nanoparticles (MNPs) with the aim of tuning their activity by magnetic heating [2, 3]. Within the frame of the FET-OPEN project HOTZYMES (https://www.hotzymes.eu), different MNPs have been synthetized and coated with polyacrylic acid and dimercaptosuccinic acid, and then were further functionalized with NTA-Cu2+ as His-tag chelating agent. Different proteins were expressed as His-tag variants and immobilized on the MNPs, including monomeric (superfolded GFP), dimeric (C. violaceum transaminase, CvTA; C. uda cellobiose phosphorylase, CuCbP), and tetrameric (B. stearothermophilus alcohol dehydrogenase, ADH) variants. While for the monomeric protein selected as model no difficulties in the bioconjugation processes were observed, when using dimeric or tetrameric enzymes the aggregation of the MNPs occurs very easily due to crosslinking between the nanoparticles. This colloidal destabilization of the MNPs is favored due to its high surface area and the presence of several tags per enzyme molecule. To avoid this situation, different strategies have been developed: saturation of the binding site of the nanoparticles, presence of a small percentage of imidazole in reaction, changes in the incubation conditions (pH, ionic strength, …). First positive results confirm that by playing with different factors it is possible to conjugate different His-tagged enzymes to very different MNPs in terms of size, shape, surface area, and colloidal stability. Actually, it is possible to avoid protein and MNPs aggregation while obtaining good activity yields for the conjugated enzymes and maintaining the magnetic heating capacity of the MNPs.The research for this work has received funding from the European Union (EU) project HOTZYMES (grant agreement n° 829162) under EU’s Horizon 2020 Programme Research and Innovation actions H2020-FETOPEN-2018-2019-2020-01. Authors also thank Spanish MINECO project BIO2017-84246-C2-1-R, DGA and Fondos Feder (Bionanosurf E15_17R).Peer reviewe

HOTZYMES - The development of efficient enzymatic cascades in well-coordinated one-pot-systems

Trabajo presentado al Workshop “Emerging technologies on Biocatalysis: present and future perspectives”, celebrado en Viena el 19 de septiembre de 2022.Peer reviewe