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Hierarchical functionalisation of the UiO-66(Zr)-NH2 metal–organic framework with cysteine, poly(ethylene glycol) (PEG), and the SARS-CoV-2 spike receptor-binding domain (RBD) was developed to enable receptor-specific interaction with the angiotensin-converting enzyme 2 receptor (ACE2) in model cells. Post-synthetic modification using cysteine and heterobifunctional PEG linkers allowed controlled bioconjugation of SpyTag-labelled RBD via SpyTag/SpyCatcher chemistry, while preserving the crystallinity, microporosity, and intrinsic optical properties of the UiO-66(Zr)-NH2 framework. Comprehensive physicochemical characterisation confirmed successful surface functionalisation, tunable aggregation behaviour, and retention of multimodal optical characteristics. Cellular studies in HEK293T and HeLa cells overexpressing EGFP-tagged ACE2 demonstrated enhanced and selective association and uptake of RBD-functionalised nanoparticles compared with non-targeted analogues. Multimodal fluorescence imaging, fluorescence lifetime imaging microscopy, flow-cytometry, and electron microscopy indicated ACE2-dependent endocytic internalisation, with predominant localisation in endosomal and autophagosomal compartments, while both amine- and cysteine-modified formulations exhibited good biocompatibility. Overall, this study establishes a virus-mimetic, ACE2-targeted UiO-66(Zr)-based nanosystem as a proof-of-concept biointerface platform for receptor-specific cellular delivery and imaging, providing a foundation for future MOF-based nanocarriers exploiting ligand–receptor interactions.

Brugada syndrome (BrS) is a genetically determined cardiac arrhythmogenic syndrome with increased risk of sudden cardiac death. BrS is mostly caused by mutations in SCN5A gene encoding the primary ɑ-subunit of the cardiac sodium channel Na V 1.5. We aimed at characterizing the functional alterations caused by the R893C mutation, identified in a proband diagnosed with BrS, and establishing whether the mutation is associated with BrS. Although several mutations have been reported in the close vicinity of R893 , the functional role of this region remains unknown and, in addition, exploring SCN5A mutations in patients with inherited arrhythmogenic syndromes is critical for understanding the pathogenesis of arrhythmias. The mutations were introduced by site-directed mutagenesis. The variants were transiently expressed in CHO cells and potassium currents were measured using the whole-cell patch clamp technique. Patch clamp recordings have demonstrated that R893C almost completely abolished the sodium current, I Na , though the mutation did not exert dominant-negative effect on wild-type Na V 1.5 channels. We also observed significant decrease in channel activation and a depolarized shift of steady–state inactivation curve, however, the kinetics of inactivation and recovery from fast inactivation were not changed by the mutation. Moreover, the reducing agent Dithiotreitol partially restored the normal function of Na V 1.5 in the R893C mutant highlighting a likely mechanism for loss of conduction via formation of disulphide bridges. We showed that R893H channels also failed to produce any detectable I Na that confirms the importance of the highly conserved R893 in gating. Our study reveals R893C is a loss-of-function mutation with altered electrophysiological characteristics of Na V 1.5. Thus, R893C may contribute to the BrS phenotype of the proband. Our findings may facilitate the understanding of the mechanisms of arrhythmogenesis in BrS, as it helps to identify mutational hotspots in BrS. Moreover, our work may improve novel gene therapy and new therapeutic drug design targeting Na V 1.5 channelopathies.

Hierarchical functionalisation of the UiO-66(Zr)-NH[sub.2] metal–organic framework with cysteine, poly(ethylene glycol) (PEG), and the SARS-CoV-2 spike receptor-binding domain (RBD) was developed to enable receptor-specific interaction with the angiotensin-converting enzyme 2 receptor (ACE2) in model cells. Post-synthetic modification using cysteine and heterobifunctional PEG linkers allowed controlled bioconjugation of SpyTag-labelled RBD via SpyTag/SpyCatcher chemistry, while preserving the crystallinity, microporosity, and intrinsic optical properties of the UiO-66(Zr)-NH[sub.2] framework. Comprehensive physicochemical characterisation confirmed successful surface functionalisation, tunable aggregation behaviour, and retention of multimodal optical characteristics. Cellular studies in HEK293T and HeLa cells overexpressing EGFP-tagged ACE2 demonstrated enhanced and selective association and uptake of RBD-functionalised nanoparticles compared with non-targeted analogues. Multimodal fluorescence imaging, fluorescence lifetime imaging microscopy, flow-cytometry, and electron microscopy indicated ACE2-dependent endocytic internalisation, with predominant localisation in endosomal and autophagosomal compartments, while both amine- and cysteine-modified formulations exhibited good biocompatibility. Overall, this study establishes a virus-mimetic, ACE2-targeted UiO-66(Zr)-based nanosystem as a proof-of-concept biointerface platform for receptor-specific cellular delivery and imaging, providing a foundation for future MOF-based nanocarriers exploiting ligand–receptor interactions.

Hierarchical functionalisation of the UiO-66(Zr)-NH metal-organic framework with cysteine, poly(ethylene glycol) (PEG), and the SARS-CoV-2 spike receptor-binding domain (RBD) was developed to enable receptor-specific interaction with the angiotensin-converting enzyme 2 receptor (ACE2) in model cells. Post-synthetic modification using cysteine and heterobifunctional PEG linkers allowed controlled bioconjugation of SpyTag-labelled RBD via SpyTag/SpyCatcher chemistry, while preserving the crystallinity, microporosity, and intrinsic optical properties of the UiO-66(Zr)-NH framework. Comprehensive physicochemical characterisation confirmed successful surface functionalisation, tunable aggregation behaviour, and retention of multimodal optical characteristics. Cellular studies in HEK293T and HeLa cells overexpressing EGFP-tagged ACE2 demonstrated enhanced and selective association and uptake of RBD-functionalised nanoparticles compared with non-targeted analogues. Multimodal fluorescence imaging, fluorescence lifetime imaging microscopy, flow-cytometry, and electron microscopy indicated ACE2-dependent endocytic internalisation, with predominant localisation in endosomal and autophagosomal compartments, while both amine- and cysteine-modified formulations exhibited good biocompatibility. Overall, this study establishes a virus-mimetic, ACE2-targeted UiO-66(Zr)-based nanosystem as a proof-of-concept biointerface platform for receptor-specific cellular delivery and imaging, providing a foundation for future MOF-based nanocarriers exploiting ligand-receptor interactions.

Brugada syndrome (BrS) is a genetically determined cardiac arrhythmogenic syndrome with increased risk of sudden cardiac death. BrS is mostly caused by mutations in gene encoding the primary ɑ-subunit of the cardiac sodium channel Na 1.5. We aimed at characterizing the functional alterations caused by the mutation, identified in a proband diagnosed with BrS, and establishing whether the mutation is associated with BrS. Although several mutations have been reported in the close vicinity of , the functional role of this region remains unknown and, in addition, exploring mutations in patients with inherited arrhythmogenic syndromes is critical for understanding the pathogenesis of arrhythmias. The mutations were introduced by site-directed mutagenesis. The variants were transiently expressed in CHO cells and potassium currents were measured using the whole-cell patch clamp technique. Patch clamp recordings have demonstrated that almost completely abolished the sodium current, I , though the mutation did not exert dominant-negative effect on wild-type Na 1.5 channels. We also observed significant decrease in channel activation and a depolarized shift of steady-state inactivation curve, however, the kinetics of inactivation and recovery from fast inactivation were not changed by the mutation. Moreover, the reducing agent Dithiotreitol partially restored the normal function of Na 1.5 in the mutant highlighting a likely mechanism for loss of conduction via formation of disulphide bridges. We showed that channels also failed to produce any detectable I that confirms the importance of the highly conserved in gating. Our study reveals is a loss-of-function mutation with altered electrophysiological characteristics of Na 1.5. Thus, may contribute to the BrS phenotype of the proband. Our findings may facilitate the understanding of the mechanisms of arrhythmogenesis in BrS, as it helps to identify mutational hotspots in BrS. Moreover, our work may improve novel gene therapy and new therapeutic drug design targeting Na 1.5 channelopathies.

EGFR is a transmembrane receptor tyrosine kinase regulating growth and survival in epithelial tissues. Its ligand, the epidermal growth factor (EGF), is produced as a membrane-anchored precursor (preEGF) that is proteolytically cleaved to release soluble EGF (sEGF). EGFR overexpression can convert it from a physiological regulator into an oncogenic driver. Therapeutic strategies targeting EGFR include monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs). Although mAbs such as cetuximab initially block EGFR activity, tumors often develop resistance. Recent findings indicate that sEGF can activate EGFR within intracellular vesicles, promoting intracrine signaling that sustains proliferation despite extracellular inhibition. Here, we investigated the mechanism of intracrine EGFR signaling in the Golgi apparatus using confocal microscopy, FRET and fluorescence correlation spectroscopy. sEGF, but not preEGF, bound and induced EGFR dimerization and phosphorylation. Erlotinib, a membrane permeable TKI, effectively blocked phosphorylation, whereas extracellular cetuximab did not. These findings imply sEGF-induced intracrine EGFR signaling in the Golgi. Our results may shed light on a potential resistance mechanism to antibody treatment.