A pH-sensitive fluorescent protein sensor to follow the pathway of calcium phosphate nanoparticles into cells

Iron-Confined CRISPR/Cas9-Ribonucleoprotein Delivery System for Redox-Responsive Gene Editing

Clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (Cas9) is a promising gene editing tool to treat diseases at the genetic level. Nonetheless, the challenge of the safe and efficient delivery of CRISPR/Cas9 to host cells constrains its clinical applicability. In the current study, a facile, redox-responsive CRISPR/Cas9-Ribonucleoprotein (RNP) delivery system by combining iron-coordinated aggregation with liposomes (Fe-RNP@L) is reported. The Fe-RNP is formed by the coordination of Fe3+ with amino and carboxyl groups of Cas9, which modifies the lipophilicity and surface charge of RNP and alters cellular uptake from primary endocytosis to endocytosis and cholesterol-dependent membrane fusion. RNP can be rapidly and reversibly released from Fe-RNP in response to glutathione without loss of structural integrity and enzymatic activity. In addition, iron coordination also improves the stability of RNP and substantially mitigates cytotoxicity. This construct enabled highly efficient cytoplasmic/nuclear delivery (≈90%) and gene-editing efficiency (≈70%) even at low concentrations. The high payload content, high editing efficiency, good stability, low immunogenicity, and ease of production and storage, highlight its potential for diverse genome editing and clinical applications.

Progress in pH-Sensitive sensors: essential tools for organelle pH detection, spotlighting mitochondrion and diverse applications

pH-sensitive fluorescent proteins have revolutionized the field of cellular imaging and physiology, offering insight into the dynamic pH changes that underlie fundamental cellular processes. This comprehensive review explores the diverse applications and recent advances in the use of pH-sensitive fluorescent proteins. These remarkable tools enable researchers to visualize and monitor pH variations within subcellular compartments, especially mitochondria, shedding light on organelle-specific pH regulation. They play pivotal roles in visualizing exocytosis and endocytosis events in synaptic transmission, monitoring cell death and apoptosis, and understanding drug effects and disease progression. Recent advancements have led to improved photostability, pH specificity, and subcellular targeting, enhancing their utility. Techniques for multiplexed imaging, three-dimensional visualization, and super-resolution microscopy are expanding the horizon of pH-sensitive protein applications. The future holds promise for their integration into optogenetics and drug discovery. With their ever-evolving capabilities, pH-sensitive fluorescent proteins remain indispensable tools for unravelling cellular dynamics and driving breakthroughs in biological research. This review serves as a comprehensive resource for researchers seeking to harness the potential of pH-sensitive fluorescent proteins.

Tuning Nanobodies' Bioactivity: Coupling to Ultrasmall Gold Nanoparticles Allows the Intracellular Interference with Survivin

Nanobodies are highly affine binders, often used to track disease-relevant proteins inside cells. However, they often fail to interfere with pathobiological functions, required for their clinical exploitation. Here, a nanobody targeting the disease-relevant apoptosis inhibitor and mitosis regulator Survivin (SuN) is utilized. Survivin's multifaceted functions are regulated by an interplay of dynamic cellular localization, dimerization, and protein-protein interactions. However, as Survivin harbors no classical "druggable" binding pocket, one must aim at blocking extended protein surface areas. Comprehensive experimental evidence demonstrates that intracellular expression of SuN allows to track Survivin at low nanomolar concentrations but failed to inhibit its biological functions. Small angle X-ray scattering of the Survivin-SuN complex locates the proposed interaction interface between the C-terminus and the globular domain, as such not blocking any pivotal interaction. By clicking multiple SuN to ultrasmall (2 nm) gold nanoparticles (SuN-N), not only intracellular uptake is enabled, but additionally, Survivin crosslinking and interference with mitotic progression in living cells are also enabled. In sum, it is demonstrated that coupling of nanobodies to nanosized scaffolds can be universally applicable to improve their function and therapeutic applicability.

Polydopamine-Coated Cu-BTC Nanowires for Effective Magnetic Resonance Imaging and Photothermal Therapy

Herein, we present a one-pot hydrothermal approach for synthesizing metal–organic framework-derived copper (II) benzene-1,3,5-tricarboxylate (Cu-BTC) nanowires (NWs) using dopamine as the reducing agent and precursor for a polydopamine (PDA) surface coating formation. In addition, PDA can act as a PTT agent and enhance NIR absorption, producing photothermal effects on cancer cells. These NWs displayed a photothermal conversion efficiency of 13.32% after PDA coating and exhibited good photothermal stability. Moreover, NWs with a suitable T1 relaxivity coefficient (r1 = 3.01 mg−1 s−1) can be effectively used as magnetic resonance imaging (MRI) contrast agents. By increasing concentrations, cellular uptake studies showed a greater uptake of Cu-BTC@PDA NWs into cancer cells. Further, in vitro studies showed PDA-coated Cu-BTC NWs possess exceptional therapeutic performance by 808 nm laser irradiation, destroying 58% of cancer cells compared with the absence of laser irradiation. This promising performance is anticipated to advance the research and implementation of copper-based NWs as theranostic agents for cancer treatment.

Self-fluorescence property of octa-arginine functionalized hydroxyapatite nanoparticles aids in studying their intracellular fate in R1 ESCs

Deciphering the endocytosis mechanisms of nanoparticle entry in cells is crucial to understand the fate of nanoparticles and the biological activity of the transported cargo. Such studies require the use of reporter agents such as fluorescent markers. Previously, we have reported the synthesis of self-fluorescent HAp nanoparticles as efficient nucleic acid delivery agents in prokaryotic and eukaryotic cells. Here, we show the application of biocompatible self-fluorescent nano delivery vehicle based on HAp and CPP- octa-arginine as an efficient system to study the mechanisms of intracellular fate of a gene delivery agent. The pathway of octa-arginine functionalized HAp NP (R8HNP) and HAp NP uptake in R1 ESCs was elucidated using confocal microscopy with the help of endocytic inhibitors. The NPs mainly enter R1 ESCs by clathrin mediated and macropinocytosis pathways. It was established that the NPs escape endosomal degradation by proton sponge effect owing to their ability to buffer the pH and trigger osmotic rupture. The functionalization of CPP, effectively enhanced the internalization and endosomal escape in R1 ESCs. The detailed results of these studies are outlined in this manuscript.

Cyclodextrin-Derived ROS-Generating Nanomedicine with pH-Modulated Degradability to Enhance Tumor Ferroptosis Therapy and Chemotherapy

Nowadays, destruction of redox homeostasis to induce cancer cell death is an emerging anti-cancer strategy. Here, the authors utilized pH-sensitive acetalated β-cyclodextrin (Ac-β-CD) to efficiently deliver dihydroartemisinin (DHA) for tumor ferroptosis therapy and chemodynamic therapy in a synergistic manner. The Ac-β-CD-DHA based nanoparticles are coated by an iron-containing polyphenol network. In response to the tumor microenvironment, Fe²⁺ /Fe³⁺ can consume glutathione (GSH) and trigger the Fenton reaction in the presence of hydrogen peroxide (H₂ O₂ ), leading to the generation of lethal reactive oxygen species (ROS). Meanwhile, the OO bridge bonds of DHA are also disintegrated to enable ferroptosis of cancer cells. Their results demonstrate that these nanoparticles acted as a ROS generator to break the redox balance of cancer cells, showing an effective anticancer efficacy, which is different from traditional approaches.

Fluorescence-based sensing of the bioenergetic and physicochemical status of the cell

Fluorescence-based sensors play a fundamental role in biological research. These sensors can be based on fluorescent proteins, fluorescent probes or they can be hybrid systems. The availability of a very large dataset of fluorescent molecules, both genetically encoded and synthetically produced, together with the structural insights on many sensing domains, allowed to rationally design a high variety of sensors, capable of monitoring both molecular and global changes in living cells or in in vitro systems. The advancements in the fluorescence-imaging field helped researchers to obtain a deeper understanding of how and where specific changes occur in a cell or in vitro by combining the readout of the fluorescent sensors with the spatial information provided by fluorescent microscopy techniques. In this review we give an overview of the state of the art in the field of fluorescent biosensors and fluorescence imaging techniques, and eventually guide the reader through the choice of the best combination of fluorescent tools and techniques to answer specific biological questions. We particularly focus on sensors for probing the bioenergetics and physicochemical status of the cell.

The endocytic pathway of Pt nanoclusters and their induced apoptosis of A549 and A549/Cis cells through c-Myc/p53 and Bcl-2/caspase-3 signaling pathways

In recent years, multifunctional platinum nanoclusters (Pt-NCs) as new Pt-based anti-cancer drugs exhibit a promising therapeutic efficiency for several cancer diseases, especially for human pulmonary carcinoma. However, the endocytosis behaviors (like uptake pathway, etc.) and induced apoptosis mechanism of Pt-NCs for drug-resistant non-small cell lung cancer (NSCLC), are still inconclusive. In this research, we explored the endocytic pathway of Pt-NCs in both typical NSCLC A549 cells and cisplatin-resistant A549/Cis cells through qualitative confocal laser scanning microscope (CLSM) measurement and quantitative flow cytometry (FCM) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) analysis, by the means of introducing the specific inhibitors which impede the classical ways of endocytosis. It was found that Pt-NCs dominatingly entered A549 cells via caveolin-mediated endocytosis as well as A549/Cis cells through micropinocytosis approach. Pt-NCs possessed an excellent inhibitory effect on the cell proliferation, migration and invasion, which the cell activity of A549 cells reduced to 14% and that of A549/Cis cells went down about four fifths. Moreover, Pt-NCs treatment increased caspase-3 protein levels and downregulated the expression of c-Myc and Bcl-2, proving the Pt-NCs-induced apoptosis of NSCLC cells was related to c-Myc/p53 and Bcl-2/caspase-3 signal pathways. These results demonstrate the explicit uptake pathway and apoptotic signaling pathway of Pt-NCs for NSCLC, which provides an in-depth and reasonable theoretical basis for the development of new Pt-NCs-based chemotherapeutics in future clinical practice.

Coating of cochlear implant electrodes with bioactive DNA-loaded calcium phosphate nanoparticles for the local transfection of stimulatory proteins

Calcium phosphate nanoparticles were loaded with nucleic acids to enhance the on-growth of tissue to a cochlear implant electrode. The nanoparticle deposition on a metallic electrode surface is possible by electrophoretic deposition (EPD) or layer-by-layer deposition (LbL). Impedance spectroscopy showed that the coating layer did not interrupt the electrical conductance at physiological frequencies and beyond (1-40,000 Hz). The transfection was demonstrated with the model cell lines HeLa and 3T3 as well as with primary explanted spiral ganglion neurons (rat) with the model protein enhanced green fluorescent protein (EGFP). The expression of the functional protein brain-derived neurotrophic factor (BDNF) was also shown. Thus, a coating of inner-ear cochlear implant electrodes with nanoparticles that carry nucleic acids will enhance the ongrowth of spiral ganglion cell axons for an improved transmission of electrical pulses.

Silica-coated calcium phosphate nanoparticles for gene silencing of NF-κB p65 by siRNA and their impact on cellular players of inflammation

The transcription factor NF-κB and its signaling cascade both play key roles in all inflammatory processes. The most critical member of the NF-κB transcription factor family is p65. We investigated the role of cationic silica-coated calcium phosphate nanoparticles (spherical, diameter by SEM 50-60 nm; zeta potential about +26 mV; stabilized by polyethyleneimine) carrying encapsulated siRNA against NF-κB p65 and their influence on inflamed cells. The nanoparticles were taken up by cells of the blood compartment involved in the inflammatory response, particularly by monocytes, and to a lesser extent by endothelial cells and B-cells, but not by T-cells. The particles were found in endolysosomes where they were dissolved at low pH and released the siRNA into the cytoplasm. This was confirmed by dissolution experiments of model nanoparticles in simulated endolysosomal medium (pH 4.7) and by intracellular co-localization studies of double-labeled nanoparticles (using a negatively charged model peptide for siRNA). The encapsulated functional siRNA reverted the p65 gene and protein expression in inflamed monocytes, the main cells in immune response and surveillance, almost back to the non-inflammatory condition. Additionally, the nanoparticles suppressed the pro-inflammatory cytokine expression profiles (TNF-α, IL-6, IFN-β) in inflamed J774A.1 monocytes. Taken together, such nanoparticles can be applied for the treatment of inflammatory diseases.

The effect of short silica fibers (0.3 μm 3.2 μm) on macrophages

Silica fibers with a dimension of 0.3 μm ∙ 3.2 μm² nm were prepared by a modified Stöber synthesis as model particles. The particles were characterized by scanning electron microscopy, elemental analysis, thermogravimetry and X-ray powder diffraction. Their uptake by macrophages (THP-1 cells and NR8383 cells) was studied by confocal laser scanning microscopy and scanning electron microscopy. The uptake by cells was very high, but the silica fibers were not harmful to NR8383 cells in concentrations up to 100 μg mL^-1. Only above 100 μg mL^-1, significant cell toxic effects were observed, probably induced by a high dose of particles that had sedimented on the cells and led to the adverse effects. The chemotactic response as assessed by the particle-induced migration assay (PICMA) was weak in comparison to a control of agglomerated silica particles. The as-prepared fibers were fully X-ray amorphous but crystallized to β-cristobalite after heating to 1000 °C and converted to α-cristobalite upon cooling to ambient temperature. The fibers had sintered to larger aggregates but retained their elongated primary shape. The particle cytotoxicity towards THP-1 cells was not significantly enhanced by the crystallization.

Biological and Medical Applications of Calcium Phosphate Nanoparticles

Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.

Subtoxic cell responses to silica particles with different size and shape

Health risks from particles are a priority challenge to health protection at work. Despite the ubiquitous exposure to a wide range of particles and the many years of research in this field, there are fundamental unresolved questions regarding the prevention of particle-related respiratory diseases. Here, the highly relevant particulate material silicon dioxide was analyzed with emphasis on defined size and shape. Silica particles were prepared with different size and shape: Spheres (NS nanospheres 60 nm; SMS submicrospheres 230 nm; MS microspheres 430 nm) and rods (SMR submicrorods with d = 125 nm, L = 230 nm; aspect ratio 1:1.8; MR microrods with d = 100 nm, L = 600 nm; aspect ratio 1:6). After an in-depth physicochemical characterization, their effects on NR8383 alveolar macrophages were investigated. The particles were X-ray amorphous, well dispersed, and not agglomerated. Toxic effects were only observed at high concentrations, i.e. ≥ 200 µg mL-1, with the microparticles showing a stronger significant effect on toxicity (MS≈MR > SMR≈SMS≈NS) than the nanoparticles. Special attention was directed to effects in the subtoxic range (less than 50% cell death compared to untreated cells), i.e. below 100 µg mL-1 where chronic health effects may be expected. All particles were readily taken up by NR8383 cells within a few hours and mainly found associated with endolysosomes. At subtoxic levels, neither particle type induced strongly adverse effects, as probed by viability tests, detection of reactive oxygen species (ROS), protein microarrays, and cytokine release (IL-1β, GDF-15, TNF-α, CXCL1). In the particle-induced cell migration assay (PICMA) with leukocytes (dHL-60 cells) and in cytokine release assays, only small effects were seen. In conclusion, at subtoxic concentrations, where chronic health effects may be expected, neither size and nor shape of the synthesized chemically identical silica particles showed harmful cell-biological effects.