Encapsulation of Nanoparticles with Statistical Copolymers with Different Surface Charges and Analysis of Their Interactions with Proteins and Cells.

Encapsulation with polymers is a well-known strategy to stabilize and functionalize nanomaterials and tune their physicochemical properties. Amphiphilic copolymers are promising in this context, but their structural diversity and complexity also make understanding and predicting their behavior challenging. This is particularly the case in complex media which are relevant for intended applications in medicine and nanobiotechnology. Here, we studied the encapsulation of gold nanoparticles and quantum dots with amphiphilic copolymers differing in their charge and molecular structure. Protein adsorption to the nanoconjugates was studied with fluorescence correlation spectroscopy, and their surface activity was studied with dynamic interfacial tensiometry. Encapsulation of the nanoparticles without affecting their characteristic properties was possible with all tested polymers and provided good stabilization. However, the interaction with proteins and cells significantly depended on structural details. We identified statistical copolymers providing strongly reduced protein adsorption and low unspecific cellular uptake. Interestingly, different zwitterionic amphiphilic copolymers showed substantial differences in their resulting bio-repulsive properties. Among the polymers tested herein, statistical copolymers with sulfobetaine and phosphatidylcholine sidechains performed better than copolymers with carboxylic acid- and dimethylamino-terminated sidechains.

Developing future nanomedicines.

Quantitative analysis of biodistribution and clearance may improve nanoparticle development.

Uptake and Intracellular Fate of Fluorophore Labeled Metal-Organic-Framework (MOF) Nanoparticles.

The uptake and the fate of Zr-based metal-organic-framework nanoparticles labeled with organic fluorophores in HeLa cells has been monitored with fluorescence detection and elemental analysis. The nanoparticles have been selected as a model system of carrier nanoparticles (here Zr-based metal-organic-framework nanoparticles) with integrated cargo molecules (here organic fluorophores), with aze that does not allow for efficient exocytosis, a material which only partly degrades under acidic conditions as present in endosomes/lysosomes, and with limited colloidal stability. Data show that, for Zr-based metal-organic-framework nanoparticles of 40 nm size as investigated here, the number of nanoparticles per cells decreases faster due to particle redistribution upon proliferation than due to nanoparticle exocytosis and that, thus, also for this system, exocytosis is not an efficient pathway for clearance of the nanoparticles from the cells.

Preparation of Selenium-Based Drug-Modified Polymeric Ligand-Functionalised Fe3O4 Nanoparticles as Multimodal Drug Carrier and Magnetic Hyperthermia Inductor.

In recent years, much effort has been invested into developing multifunctional drug delivery systems to overcome the drawbacks of conventional carriers. Magnetic nanoparticles are not generally used as carriers but can be functionalised with several different biomolecules and their size can be tailored to present a hyperthermia response, allowing for the design of multifunctional systems which can be active in therapies. In this work, we have designed a drug carrier nanosystem based on Fe3O4 nanoparticles with large heating power and 4-amino-2-pentylselenoquinazoline as an attached drug that exhibits oxidative properties and high selectivity against a variety of cancer malignant cells. For this propose, two samples composed of homogeneous Fe3O4 nanoparticles (NPs) with different sizes, shapes, and magnetic properties have been synthesised and characterised. The surface modification of the prepared Fe3O4 nanoparticles has been developed using copolymers composed of poly(ethylene-alt-maleic anhydride), dodecylamine, polyethylene glycol and the drug 4-amino-2-pentylselenoquinazoline. The obtained nanosystems were properly characterised. Their in vitro efficacy in colon cancer cells and as magnetic hyperthermia inductors was analysed, thereby leaving the door open for their potential application as multimodal agents.

Enabling X-ray fluorescence imaging for in vivo immune cell tracking.

The infiltration of immune cells into sites of inflammation is one key feature of immune mediated inflammatory diseases. A detailed assessment of the in vivo dynamics of relevant cell subtypes could booster the understanding of this disease and the development of novel therapies. We show in detail how advanced X-ray fluorescence imaging enables such quantitative in vivo cell tracking, offering solutions that could pave the way beyond what other imaging modalities provide today. The key for this achievement is a detailed study of the spectral background contribution from multiple Compton scattering in a mouse-scaled object when this is scanned with a monochromatic pencil X-ray beam from a synchrotron. Under optimal conditions, the detection sensitivity is sufficient for detecting local accumulations of the labelled immune cells, hence providing experimental demonstration of in vivo immune cell tracking in mice.

Overcoming Non-Specific Interactions for Efficient Encapsulation of Doxorubicin in Ferritin Nanocages for Targeted Drug Delivery.

Due to its beneficial pharmacological properties, ferritin (Ftn) is considered as an interesting drug delivery vehicle to alleviate the cardiotoxicity of doxorubicin (DOX) in chemotherapy. However, the encapsulation of DOX in Ftn suffers from heavy precipitation and low protein recovery yield which limits its full potential. Here, a new DOX encapsulation strategy by cysteine-maleimide conjugation is proposed. In order to demonstrate that this strategy is more efficient compared to the other approaches, DOX is encapsulated in Ftn variants carrying different surface charges. Furthermore, in contrast to the common belief, this data show that DOX molecules are also found to bind non-specifically to the surface of Ftn. This can be circumvented by the use of Tris(2-carboxyethyl)phosphine (TCEP) during encapsulation or by washing with acidic buffer. The biocompatibility studies of the resulting DOX Ftn variants in MCF-7 and MHS cancer cells shows a complex relationship between the cytotoxicity, the DOX loading and the different surface charges of Ftn. Further investigation on the cell uptake mechanism provides reasonable explanations for the cytotoxicity results and reveals that surface charging of Ftn hinders its transferrin receptor 1 (TfR-1) mediated cellular uptake in MCF-7 cells.

Quantitative Comparison of Gold Nanoparticle Delivery via the Enhanced Permeation and Retention (EPR) Effect and Mesenchymal Stem Cell (MSC)-Based Targeting.

There are still some gaps in existing knowledge in the field of cancer nanotheranostics, e.g., the efficiency of nanoparticle-loaded cells for targeted delivery. In the current study, gold nanoparticles (Au NPs) were delivered to tumors in both subcutaneous tumor and lung metastasis tumor models by intravenous injection of either free Au NPs or of human bone marrow mesenchymal stem cells (MSCs), which were loaded with endocytosed Au NPs. By making injections with the same dose of administrated Au NPs, it was possible to directly compare tumor targeting of both delivery modes. Hereby, the passive targeting of tumor by the plain Au NPs was facilitated by the enhanced permeation and retention (EPR) effect. Au NP retention by tumors, as well as tumor penetration, were found to be improved up to 2.4-to-9.3-fold when comparing the MSC-mediated delivery of Au NPs to the delivery of the plain Au NPs via EPR effect on day 7 post administration. While the absolute retention of Au NPs in the tumor remained low, our data show that, upon injection of the same amount of Au NPs, in fact MSC-mediated delivery is quantitatively higher than EPR-mediated delivery of NPs by half an order of magnitude.

Probing the Cellular Fate of the Protein Corona around Nanoparticles with Nanofocused X-ray Fluorescence Imaging.

X-ray fluorescence imaging (XRF-imaging) with subcellular resolution is used to study the intracellular integrity of a protein corona that was pre-formed around gold nanoparticles (AuNP). Artificial proteins engineered to obtain Gd coordination for detection by XRF-imaging were used to form the corona. Indications about the degradation of this protein corona at a cellular and subcellular level can be observed by following the Au and Gd quantities in a time and spatial-dependent manner. The extended acquisition times necessary for capturing individual XRF-imaging cell images result in relatively small sample populations, stressing the need for faster image acquisition strategies in future XRF-imaging-based studies to deal with the inherent variability between cells. Still, results obtained reveal degradation of the protein corona during cellular trafficking, followed by differential cellular processing for AuNP and Gd-labelled proteins. Overall, this demonstrates that the dynamic degradation of the protein corona can be tracked by XRF-imaging to a certain degree.

Size- and Ligand-Dependent Transport of Nanoparticles in Matricaria chamomilla as Demonstrated by Mass Spectroscopy and X-ray Fluorescence Imaging.

Matricaria chamomilla flowers were incubated with gold nanoparticles of different sizes ranging from 1.4 to 94 nm. After different incubation times of 6, 12, 24, and 48 h, the gold distribution in the flowers was destructively measured by inductively coupled plasma mass spectrometry (ICP-MS) and non-destructively measured by X-ray fluorescence imaging (XFI) with high lateral resolution. As a control, the biodistribution of iodine ions or iodine-containing organic molecules (iohexol) was determined, in order to demonstrate the feasibility of mapping the distribution of several elements in parallel. The results show a clear size-dependent transport of the nanoparticles. In addition, the surface chemistry also plays a decisive role in disposition. Only the 1.6 nm nanoparticles coated with acetylcysteine could be efficiently transported through the stem of the flowers into the petals. In this case, almost 80% of the nanoparticles which were found within each flower were located in the petals. The study also highlights the potential of XFI for in situ recording of in vivo analyte biodistribution.

X-Ray Photon Correlation Spectroscopy Towards Measuring Nanoparticle Diameters in Biological Environments Allowing for the In Situ Analysis of their Bio-Nano Interface.

X-ray photon correlation spectroscopy (XPCS), a synchrotron source-based technique to measure sample dynamics, is used to determine hydrodynamic diameters of gold nanoparticles (Au NPs) of different sizes in biological environments. In situ determined hydrodynamic diameters are benchmarked with values obtained by dynamic light scattering. The technique is then applied to analyze the behavior of the Au NPs in a biological environment. First, a concentration-dependent agglomeration in the presence of NaCl is determined. Second, concentration-dependent increase in hydrodynamic diameter of the Au NPs upon the presence of proteins is determined. As X-rays in the used energy range are barely scattered by biological matter, dynamics of the Au NPs can be also detected in situ in complex biological environments, such as blood. These measurements demonstrate the possibility of XPCS for in situ analytics of nanoparticles (NPs) in biological environments where similar detection techniques based on visible light would severely suffer from scattering, absorption, and reflection effects.

In-situ x-ray fluorescence imaging of the endogenous iodine distribution in murine thyroids.

X-ray fluorescence imaging (XFI) is a non-invasive detection method of small quantities of elements, which can be excited to emit fluorescence x-ray photons upon irradiation with an incident x-ray beam. In particular, it can be used to measure nanoparticle uptake in cells and tissue, thus making it a versatile medical imaging modality. However, due to substantially increased multiple Compton scattering background in the measured x-ray spectra, its sensitivity severely decreases for thicker objects, so far limiting its applicability for tracking very small quantities under in-vivo conditions. Reducing the detection limit would enable the ability to track labeled cells, promising new insights into immune response and pharmacokinetics. We present a synchrotron-based approach for reducing the minimal detectable marker concentration by demonstrating the feasibility of XFI for measuring the yet inaccessible distribution of the endogenous iodine in murine thyroids under in-vivo conform conditions. This result can be used as a reference case for the design of future preclinical XFI applications as mentioned above.

Quantitative considerations about the size dependence of cellular entry and excretion of colloidal nanoparticles for different cell types.

Most studies about the interaction of nanoparticles (NPs) with cells have focused on how the physicochemical properties of NPs will influence their uptake by cells. However, much less is known about their potential excretion from cells. However, to control and manipulate the number of NPs in a cell, both cellular uptake and excretion must be studied quantitatively. Monitoring the intracellular and extracellular amount of NPs over time (after residual noninternalized NPs have been removed) enables one to disentangle the influences of cell proliferation and exocytosis, the major pathways for the reduction of NPs per cell. Proliferation depends on the type of cells, while exocytosis depends in addition on properties of the NPs, such as their size. Examples are given herein on the role of these two different processes for different cells and NPs.

Influence of the chirality of carbon nanodots on their interaction with proteins and cells.

Carbon nanodots with opposite chirality possess the same major physicochemical properties such as optical features, hydrodynamic diameter, and colloidal stability. Here, a detailed analysis about the comparison of the concentration of both carbon nanodots is carried out, putting a threshold to when differences in biological behavior may be related to chirality and may exclude effects based merely on differences in exposure concentrations due to uncertainties in concentration determination. The present study approaches this comparative analysis evaluating two basic biological phenomena, the protein adsorption and cell internalization. We find how a meticulous concentration error estimation enables the evaluation of the differences in biological effects related to chirality.

Influence of the Modulation of the Protein Corona on Gene Expression Using Polyethylenimine (PEI) Polyplexes as Delivery Vehicle.

The protein corona can significantly modulate the physicochemical properties and gene delivery of polyethylenimine (PEI)/DNA complexes (polyplexes). The effects of the protein corona on the transfection have been well studied in terms of averaged gene expression in a whole cell population. Such evaluation methods give excellent and reliable statistics, but they in general provide the final transfection efficiency without reflecting the dynamic process of gene expression. In this regard the influence of bovine serum albumin (BSA) on the gene expression of PEI polyplexes also on a single cell level via live imaging is analyzed. The results reveal that although the BSA corona causes difference in the overall gene expression and mRNA transcription, the gene expression behavior on the level of individual cell is similar, including the mitosis-dependent expression, distributions of onset time, expression pattern in two daughter cells, and expression kinetics in successfully transfected cells. Comparison of single cell and ensemble data on whole cell cultures indicate that the protein corona does not alter the transfection process after nuclear entry, including cell division, polyplex dissociation, and protein expression. Its influence on other steps of in vitro gene delivery before nuclear entry shall render the difference in the overall transfection.

Stimulation of Local Cytosolic Calcium Release by Photothermal Heating for Studying Intra- and Intercellular Calcium Waves.

A methodology is described that allows for localized Ca2+ release by photoexcitation. For this, cells are loaded with polymer capsules with integrated plasmonic nanoparticles, which reside in endo-lysosomes. The micrometer-sized capsules can be individually excited by near-infrared light from a light pointer, causing photothermal heating, upon which there is a rise in the free cytosolic Ca2+ concentration ([Ca2+ ]i ). The [Ca2+ ]i can be analyzed with a Ca2+ indicator fluorophore. In this way, it is possible to excite local lysosomal Ca2+ release in a desired target cell.

X-ray Fluorescence Uptake Measurement of Functionalized Gold Nanoparticles in Tumor Cell Microsamples.

Quantitative cellular in vitro nanoparticle uptake measurements are possible with a large number of different techniques, however, all have their respective restrictions. Here, we demonstrate the application of synchrotron-based X-ray fluorescence imaging (XFI) on prostate tumor cells, which have internalized differently functionalized gold nanoparticles. Total nanoparticle uptake on the order of a few hundred picograms could be conveniently observed with microsamples consisting of only a few hundreds of cells. A comparison with mass spectroscopy quantification is provided, experimental results are both supported and sensitivity limits of this XFI approach extrapolated by Monte-Carlo simulations, yielding a minimum detectable nanoparticle mass of just 5 pg. This study demonstrates the high sensitivity level of XFI, allowing non-destructive uptake measurements with very small microsamples within just seconds of irradiation time.

X-ray-Based Techniques to Study the Nano-Bio Interface.

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

Nanotoxicology and Nanomedicine: The Yin and Yang of Nano-Bio Interactions for the New Decade.

Nanotoxicology and nanomedicine are two sub-disciplines of nanotechnology focusing on the phenomena, mechanisms, and engineering at the nano-bio interface. For the better part of the past three decades, these two disciplines have been largely developing independently of each other. Yet recent breakthroughs in microbiome research and the current COVID-19 pandemic demonstrate that holistic approaches are crucial for solving grand challenges in global health. Here we show the Yin and Yang relationship between the two fields by highlighting their shared goals of making safer nanomaterials, improved cellular and organism models, as well as advanced methodologies. We focus on the transferable knowledge between the two fields as nanotoxicological research is moving from pristine to functional nanomaterials, while inorganic nanomaterials - the main subjects of nanotoxicology - have become an emerging source for the development of nanomedicines. We call for a close partnership between the two fields in the new decade, to harness the full potential of nanotechnology for benefiting human health and environmental safety.

Multimodal Imaging of Pancreatic Ductal Adenocarcinoma Using Multifunctional Nanoparticles as Contrast Agents.

Late diagnosis and refractory behavior toward current treatment protocols make pancreatic ductal adenocarcinoma (PDAC) one of the most difficult cancer forms to treat. The imaging-based approach plays an important role to identify potentially curable PDAC patients in high-risk groups at the early stage. In the present study, we developed a core-shell structured gold nanorod (AuNR) as a contrast agent for multimodal imaging and investigated its application for PDAC diagnosis. The composite nanoparticles composed of a AuNR core inside a layer of mesoporous silica that was then coated with a gadolinium oxide carbonate shell (AuNR-SiO2-Gd) are designed to be used in magnetic resonance imaging (MRI), X-ray computed tomography (CT), and photoacoustic imaging (PAI). A phantom study with the AuNR-SiO2-Gd NPs demonstrated higher MRI contrast compared to Gadovist and higher X-ray attenuation than Visipaque. A strong, stable, and broad wavelength range signal with a peak at 800 nm was observed in PAI. The AuNR-SiO2-Gd NPs showed significant contrast enhancement under PAI/MRI/CT in both the liver and spleen of control mice after intravenous administration. The utility in PDAC was studied in a genetically engineered mouse model carrying Kras and p53 mutations, which develops spontaneous tumors and keeps the desmoplasia and hypovascularity feature of PDAC in patients. The AuNR-SiO2-Gd NPs were highly accumulated in the surrounding soft tissues but were sparsely distributed throughout the tumor due to dense stroma infiltration and poor tumor vascularization. Hence, a negative contrast within the tumor area in CT/PAI and a positive contrast in MRI were observed. In conclusion, AuNR-SiO2-Gd NPs have good potential to be developed as a multimodal contrast agent for PDAC, which might improve early diagnosis and benefit the clinical outcome for PDAC patients.