Interaction of Nanoparticles with Cells

Dynamics and Physics of Integrin Activation in Tumor Cells by Nano-Sized Extracellular Ligands and Electromagnetic Fields

Integrins are stress-sensing proteins expressed on the surface of cells. They regulate bidirectional signal transduction during cell-cell or cell-extracellular matrix (ECM) contacts. Integrins link the ECM with the cytoplasm through interaction with their ligands. Biophysically, such interactions can be understood as changes in stress fields at specific integrin stress-sensing domains, such as the MIDAS and ADMIDAS domains. Stress changes between ligands and cytoskeletal structures are involved in cancer cell growth by altering signal transduction pathways dependent on integrin activation. In this chapter, previous results regarding integrin activation and tumor cell growth using nanoparticles (NPs) of different materials, sizes and shapes are placed within a framework of polarized NPs in the ECM by external electromagnetic fields, in which the synergic action between polarized NPs and electromagnetic fields activates the integrins. Small size NPs activate integrins via the polar component of the dipole force between NPs and integrin sensing stress sites, while large size NPs exercise a similar action via the radial component. A quantum electrodynamic model also accounts for ECM overstressing by electromagnetic mode trapping between coherent symmetric and antisymmetric quantum states.

Stimuli-Responsive Aliphatic Polycarbonate Nanocarriers for Tumor-Targeted Drug Delivery

Nanoparticles based on amphiphilic copolymers with tunable physicochemical properties can be used to encapsulate delicate pharmaceutics while at the same time improving their solubility, stability, pharmacokinetic properties, reducing immune surveillance, or achieving tumor-targeting ability. Those nanocarriers based on biodegradable aliphatic polycarbonates are a particularly promising platform for drug delivery due to flexibility in the design and synthesis of appropriate monomers and copolymers. Current studies in this field focus on the design and the synthesis of new effective carriers of hydrophobic drugs and their release in a controlled manner by exogenous or endogenous factors in tumor-specific regions. Reactive groups present in aliphatic carbonate copolymers, undergo a reaction under the action of a stimulus: e.g., acidic hydrolysis, oxidation, reduction, etc. leading to changes in the morphology of nanoparticles. This allows the release of the drug in a highly controlled manner and induces a desired therapeutic outcome without damaging healthy tissues. The presented review summarizes the current advances in chemistry and methods for designing stimuli-responsive nanocarriers based on aliphatic polycarbonates for controlled drug delivery.

Exploring Diffusion and Cellular Uptake: Charged Gold Nanoparticles in an in Vitro Breast Cancer Model

Gold nanoparticles have emerged as a prominent tool in nanomedicine, particularly for applications in cancer diagnostic and treatment. One of the challenges for the successful implementation of gold nanoparticles in cancer therapy is their delivery to the specific cancer area within the tumor microenvironment. The presence of cancer enables a poorly organized vascularization system, increasing the pressure with the microenvironment, limiting the uptake of particles. The physicochemical properties of the gold nanoparticles (size, shape, and surface charge) also have a significant effect on diffusion to the tumor site and cellular uptake. In this work, we analyzed the transport of 10 nm gold nanoparticles with different surface charges (neutral, negative, and positive) through a hydrogel composite. Three-dimensional in vitro models composed of breast cancer cells loaded in the hydrogel composite were used for the qualitative and quantitative evaluation of cellular uptake of the gold nanoparticles. Surprisingly, an inverse correlation between the diffusion coefficients of the nanoparticles and cellular uptake was demonstrated. Positively charged gold nanoparticles displayed high cellular uptake, although their diffusion coefficient indicated slow transport through the hydrogel matrix. Neutral particles, on the other hand, displayed fast diffusion but the lowest cellular uptake. The results obtained indicate that nanoparticle diffusion and cellular uptake should be studied together in realistic in vitro models for a true evaluation of transport in tumor microenvironments.

Formation of aggregates, icosahedral structures and percolation clusters of fullerenes in lipids bilayers: The key role of lipid saturation

Carbon nanoparticles (CNPs) are attractive materials for a great number of applications but there are serious concerns regarding their influence on health and environment. Here, our focus is on the behavior of fullerenes in lipid bilayers with varying lipid saturations, chain lengths and fullerene concentrations using coarse-grained molecular dynamics (CG-MD) simulations. Our findings show that the lipid saturation level is a key factor in determining how fullerenes behave and where the fullerenes are located inside a lipid bilayer. In saturated and monounsaturated bilayers fullerenes aggregated and formed clusters with some of them showing icosahedral structures. In polyunsaturated lipid bilayers, no such structures were observed: In polyunsaturated lipid bilayers at high fullerene concentrations, connected percolation-like networks of fullerenes spanning the whole lateral area emerged at the bilayer center. In other systems only separate isolated aggregates were observed. The effects of fullerenes on lipid bilayers depend strongly on fullerene aggregation. When fullerenes aggregate, their interactions with the lipid tails change.

Cellular fate of deformable needle-shaped PLGA-PEG fibers

Deformability of micro/nanometer sized particles plays an important role in particle-cell interactions and thus becomes a key parameter in carrier design in biomedicine application such as drug delivery and vaccinology. Yet the influence of material's deformability on the cellular fate of the particles as well as physiology response of live cells are to be understood. Here we show the cellular fate of needle shaped (high aspect ratio ~25) PLGA-PEG copolymer fibers depending on their deformability. We found that all the fibers entered murine macrophage cells (RAW 264.7) via phagocytosis. While the fibers of high apparent Young's modulus (average value = 872 kPa) maintained their original shape upon phagocytosis, their counterparts of low apparent Young's modulus (average value = 56 kPa) curled in cells. The observed deformation of fibers of low apparent Young's modulus in cells coincided with abnormal intracellular actin translocation and absence of lysosome/phagosome fusion in macrophages, suggesting the important role of material mechanical properties and mechano-related cellular pathway in affecting cell physiology. STATEMENT OF SIGNIFICANCE: Particles are increasingly important in the field of biomedicine, especially when they are serving as drug carriers. Physical cues, such as mechanical properties, were shown to provide insight into their stability and influence on physiology inside the cell. In the current study, we managed to fabricate 5 types of needle shaped PLGA-PEG fibers with controlled Young's modulus. We found that hard fibers maintained their original shape upon phagocytosis, while soft fibers were curled by actin compressive force inside the cell, causing abnormal actin translocation and impediment of lysosome/phagosome fusion, suggesting the important role of material mechanical properties and mechano-related cellular pathway in affecting cell physiology.

Endothelial Cell Targeting by cRGD-Functionalized Polymeric Nanoparticles under Static and Flow Conditions

Since α_vβ₃ integrin is a key component of angiogenesis in health and disease, Arg-Gly-Asp (RGD) peptide-functionalized nanocarriers have been investigated as vehicles for targeted delivery of drugs to the α_vβ₃ integrin-overexpressing neovasculature of tumors. In this work, PEGylated nanoparticles (NPs) based on poly(lactic-co-glycolic acid) (PLGA) functionalized with cyclic-RGD (cRGD), were evaluated as nanocarriers for the targeting of angiogenic endothelium. For this purpose, NPs (~300 nm) functionalized with cRGD with different surface densities were prepared by maleimide-thiol chemistry and their interactions with human umbilical vein endothelial cells (HUVECs) were evaluated under different conditions using flow cytometry and microscopy. The cell association of cRGD-NPs under static conditions was time-, concentration- and cRGD density-dependent. The interactions between HUVECs and cRGD-NPs dispersed in cell culture medium under flow conditions were also time- and cRGD density-dependent. When washed red blood cells (RBCs) were added to the medium, a 3 to 8-fold increase in NPs association to HUVECs was observed. Moreover, experiments conducted under flow in the presence of RBC at physiologic hematocrit and shear rate, are a step forward in the prediction of in vivo cell–particle association. This approach has the potential to assist development and high-throughput screening of new endothelium-targeted nanocarriers.

Leveraging Electrostatic Interactions for Drug Delivery to the Joint

Arthritis is a debilitating joint disease with a high economic burden and prevalence. There are many challenges delivering therapeutics to the joint, including low bioavailability when administered systemically and low joint retention after intra-articular injection. Therefore, drug delivery systems such as nanoparticles, liposomes, dendrimers, and carrier proteins have been utilized to overcome some of these limitations. To enhance joint tissue localization and retention, there are opportunities to leverage electrostatic interactions between drug carriers and various tissues and cells. These opportunities, as they pertain to specific joint tissues, are explored in this review. Further, the impact that electrostatic interactions has on various drug delivery parameters, such as the formation of a protein corona, the uptake and cytotoxicity, and the biodistribution of the drug delivery systems, is discussed. Lastly, this review summarizes key findings from studies that have investigated the use of electrostatic interactions to increase targeting of specific joint tissues and limitations in preclinical investigations are identified. As more novel targets are discovered in treating arthritis, there will be a continued need to localize therapeutics to specific tissues for greater therapeutic outcomes and hence attention must be paid in designing the drug delivery systems.

Size-Controlled Preparation and Behavior Study of Phospholipid-Calcium Carbonate Hybrid Nanoparticles

Background

Calcium carbonate (CC) nanoparticles have broad biomedical utilizations, owing to their multiple intrinsic merits. However, bare CC nanoparticles do not allow for the development of multifunctional devices suitable for advanced drug delivery in cancer therapy.

Methods

Phospholipid-modified phospholipid–CC hybrid nanoparticles were prepared in our study using a combination of vapor-diffusion and solvent-diffusion methods to offer optimized pharmaceutical capabilities.

Results

Considering that particle size is a critical parameter that plays an important role in both in vitro and in vivo behaviors of nanoparticles, we here for the first time a present detailed protocol for the size-controlled preparation of hybrid nanoparticles, as well as analysis of the in vitro/in vivo behaviors of differently sized hybrid nanoparticles.

Conclusion

Our results might significantly advance the application of this promising material in more varied fields.

GLUT-1: An Effective Target To Deliver Brain-Derived Neurotrophic Factor Gene Across the Blood Brain Barrier

Alzheimer's disease (AD), the most common cause of dementia, inflicts enormous suffering to patients and their family members. It is the third deadliest disease, affecting 46.8 million people worldwide. Brain-derived neurotrophic factor (BDNF) is involved in the development, maintenance, and plasticity of the central nervous system. This crucial protein is significantly reduced in AD patients leading to reduced plasticity and neuronal death. In this study, we demonstrate the targeted delivery of the BDNF gene to the brain using liposome nanoparticles. These liposomes were surface modified with glucose transporter-1 targeting ligand (mannose) and cell penetrating peptides (penetratin or rabies virus glycoprotein) to promote selective and enhanced delivery to the brain. Surface modified liposomes showed significantly higher transfection of BDNF in primary astrocytes and neurons, compared to unmodified (plain) liposomes. BDNF transfection via dual modified liposomes resulted in an increase in presynaptic marker synaptophysin protein in primary neuronal cells, which is usually found to be reduced in AD patients. Liposomes surface modified with mannose and cell penetrating peptides demonstrated ∼50% higher transport across the in vitro blood brain barrier (BBB) model and showed significantly higher transfection efficiency in primary neuronal cells compared to plain liposomes. These results were correlated with significantly higher transport of surface modified liposomes (∼7% of injected dose/gram of tissue) and BDNF transfection (∼1.7 times higher than baseline level) across BBB following single intravenous administration in C57BL/6 mice without any signs of inflammation or toxicity. Overall, this study suggests a safe and targeted strategy to increase BDNF protein in the brain, which has the potential to reverse AD pathophysiology.

Iron Oxide Nanoparticles as Carriers for DOX and Magnetic Hyperthermia after Intratumoral Application into Breast Cancer in Mice: Impact and Future Perspectives

There is still a need for improving the treatment of breast cancer with doxorubicin (DOX). In this paper, we functionalized magnetic nanoparticles (MNPs) with DOX and studied the DOX-induced antitumor effects in breast cancer cells (BT474) in the presence of magnetic hyperthermia (43 °C, 1 h). We show that i) intratumoral application of DOX-functionalized MNPs (at least at a concentration of 9.6 nmol DOX/100 mm³ tumor volume) combined with magnetic hyperthermia favors tumor regression in vivo, and there is evidence for an increased effect compared to magnetic hyperthermia alone or to the intratumoral application of free DOX and ii) the presence of the pseudopeptide NucAnt (N6L) on the MNP surface might well be beneficial in its function as carrier for MNP internalization into breast cancer cells in vitro, which could further augment the possibility of the induction of intracellular heating spots and cell death in the future.

Schwann Cell Migration through Magnetic Actuation Mediated by Fluorescent-Magnetic Bifunctional Fe3O4·Rhodamine 6G@Polydopamine Superparticles

Peripheral nerve injuries always cause dysfunction but without ideal strategies to assist the treatment and recovery successfully. The primary way to repair the peripheral nerve injuries is to bridge the lesions by promoting axon regeneration. Schwann cells acting as neuroglial cells play a pivotal role during axonal regeneration. The orderly and organized migration of Schwann cells is beneficial for the extracellular matrix connection and Büngner bands formation, which greatly promote the regeneration of axons by offering mechanical support and growth factors. Thus, the use of Schwann cells as therapeutic cells offers us an attractive method for neurorepair therapies, and the ability to direct and manipulate Schwann cell migration and distribution is of great significance in the field of cell therapy in regards to the repair and regeneration of the peripheral nerve. Herein, we design and characterize a type of novel fluorescent-magnetic bifunctional Fe₃O₄·Rhodamine 6G (R6G)@polydopamine (PDA) superparticles (SPs) and systematically study the biological behaviors of Fe₃O₄·R6G@PDA SP uptake by Schwann cells. The results demonstrate that our tailor-made Fe₃O₄·R6G@PDA SPs can be endocytosed by Schwann cells and then highly magnetize Schwann cells by virtue of their excellent biocompatibility. Furthermore, remote-controlling and noninvasive magnetic targeting migration of Schwann cells can be achieved on the basis of the high magnetic responsiveness of Fe₃O₄·R6G@PDA SPs. At the end, gene expression profile analysis is performed to explore the mechanism of Schwann cells' magnetic targeting migration. The results indicate that cells can sense external magnetic mechanical forces and transduce into intracellular biochemical signaling, which stimulate gene expression associated with Schwann cell migration.

Growth and elongation of axons through mechanical tension mediated by fluorescent-magnetic bifunctional Fe3O4·Rhodamine 6G@PDA superparticles

Background

The primary strategy to repair peripheral nerve injuries is to bridge the lesions by promoting axon regeneration. Thus, the ability to direct and manipulate neuronal cell axon regeneration has been one of the top priorities in the field of neuroscience. A recent innovative approach for remotely guiding neuronal regeneration is to incorporate magnetic nanoparticles (MNPs) into cells and transfer the resulting MNP-loaded cells into a magnetically sensitive environment to respond to an external magnetic field. To realize this intention, the synthesis and preparation of ideal MNPs is an important challenge to overcome.

Results

In this study, we designed and prepared novel fluorescent-magnetic bifunctional Fe₃O₄·Rhodamine 6G@polydopamine superparticles (FMSPs) as neural regeneration therapeutics. With the help of their excellent biocompatibility and ability to interact with neural cells, our in-house fabricated FMSPs can be endocytosed into cells, transported along the axons, and then aggregated in the growth cones. As a result, the mechanical forces generated by FMSPs can promote the growth and elongation of axons and stimulate gene expression associated with neuron growth under external magnetic fields.

Conclusions

Our work demonstrates that FMSPs can be used as a novel stimulator to promote noninvasive neural regeneration through cell magnetic actuation.

Influence of Core Cross-Linking and Shell Composition of Polymeric Micelles on Immune Response and Their Interaction with Human Monocytes

Block copolymer micelles have received increasing attention in the last decades, in particular for their appealing properties in nanomedicine. However, systematic investigations of the interaction between polymeric micelles and immune cells are still rare. Therefore, broader studies comparing the structural effects remain inevitable for a comprehensive understanding of the immune response and for the design of efficient, nonimmunogenic delivery systems. Here, we present novel block copolymer micelles with the same hydrophobic core, based on a copolymer of BA and VDM, and various hydrophilic shells ranging from common PEG derivatives to morpholine-based materials. The influence of these shells on innate immune responses was studied in detail. In addition, we investigated the impact of micelle stability by varying the cross-linking density in the micellar core. Surprisingly, whereas different shells had only a minor impact on immune response, micelles with reduced cross-linking density considerably enhanced the release of cytokines from isolated human monocytes. Moreover, the uptake of non-cross-linked micelles by monocytes was significantly higher as compared to cross-linked materials. Our study emphasizes the importance of the micellar stability on the interaction with the immune system, which is the key for any stealth properties in vivo. Polymers based on morpholines result in a similar low response as the PEG derivative and may represent an interesting alternative to the common PEGylation.

A pH and reduction dual-sensitive polymeric nanomicelle for tumor microenvironment triggered cellular uptake and controlled intracellular drug release

Minimal drug leakage during blood circulation and intracellular drug delivery in tumor sites are of great significance in chemotherapeutics. Herein we propose an interlayer crosslinked polymeric micelle with tumor acidity and reduction dual sensitivity for highly efficient drug delivery to cancer cells. A novel copolymer mPEG-C[double bond, length as m-dash]N-PAsp(MEA)-CA was synthesized and self-assembled into a dual-sensitive interlayer-crosslinked micelle (ICM). The micelle was composed of a tumor acidity sheddable PEG outer layer, a reduction-sensitive disulfide-crosslinked interlayer (PAsp(MEA)) and a hydrophobic core of cholic acid (CA) for doxorubicin (DOX) delivery. The nano-sized ICM was stable and showed little drug leakage in a neutral physiological environment. In tumor microenvironments (TMEs) with mild acidity, the PEG outer layer was readily detached due to the hydrolysis of the Schiff base linker, and the surface of the ICM was switched to positively charged to enhance the cellular uptake. Furthermore, inside tumor cells DOX was rapidly released due to the reduction of disulfide bonds by glutathione (GSH). The DOX-loaded ICM exhibited an effective anticancer effect against C6 glioma and reduced side effects both in vitro and in vivo. The study reveals that this pH and reduction dual-sensitive micelle may have great potential to mediate effective anticancer therapy.

Au nanozyme-driven antioxidation for preventing frailty

From senescence and frailty that may result from various biological, mechanical, nutritional, and metabolic processes, the human body has its own antioxidant defense enzymes to remove by-products of oxygen metabolism, and if unregulated, can cause several types of cell damage. Herein, an antioxidant, artificial nanoscale enzyme, called nanozyme (NZs), is introduced that is composed of Au nanoparticles (NPs) synthesized with a mixture of two representative phytochemicals, namely, gallic acid (GA) and isoflavone (IF), referred to as GI-Au NZs. Their unique antioxidant and anti-aging effects are monitored using Cell Counting Kit-8 and senescence-associated β-galactosidase assays on neonatal human dermal fibroblasts (nHDFs). Furthermore, alterations in epidermal thickness and SOD activity are measured under ultraviolet light to investigate the effects of the topical application of NZs on the histological structure and antioxidant activity in hairless mice skin. Then, hepatotoxicity and nephrotoxicity in the hairless mice are monitored. It is concluded that the NZs can effectively prevent serial passage-induced senescence in nHDFs, as well as oxidative stress in mice skin, suggesting a range of strategies to further develop novel therapeutics for acute frailty.

Probing Nanoparticle/Membrane Interactions by Combining Amphiphilic Diblock Copolymer Assembly and Plasmonics

Understanding the interactions between nanoparticles (NPs) and boundaries of cells is crucial both for their toxicity and therapeutic applications. Besides specific receptor-mediated endocytosis of surface-functionalized NPs, passive internalization is prompted by relatively unspecific parameters, such as particle size and charge. Based on theoretical treatments, adhesion to and bending of the cell membrane can induce NP wrapping. Experimentally, powerful tools are needed to selectively probe possible membrane-NP motifs at very dilute conditions and avoid dye labeling. In this work, we employ surface resonance-enhanced dynamic light scattering, surface plasmon resonance, electron microscopy, and simulations for sensing interactions between plasmonic AuNPs and polymersomes. We distinguish three different interaction scenarios at nanomolar concentrations by tuning the surface charge of AuNPs and rationalize these events by balancing vesicle bending and electrostatic/van der Waals AuNP and vesicle adhesion. The clarification of the physical conditions under which nanoparticles passively translocate across membranes can aid in the rational design of drugs that cannot exploit specific modes of cellular uptake and also elucidates physical properties that render nanoparticles in the environment particularly toxic.

Ultrasound monitoring of magnet-guided delivery of mesenchymal stem cells labeled with magnetic lipid–polymer hybrid nanobubbles

Mesenchymal stem cells labeled with positively charged magnetic lipid–polymer hybrid nanobubbles could be tracked for magnet-guided delivery onto the site of an injured artery using ultrasound.

ESR as a monitoring method of the interactions between TEMPO-functionalized magnetic nanoparticles and yeast cells

Potential application of magnetic nanoparticles as drug carriers in medical treatment requires prior determination of their effects on cells. In this work different spin labels and magnetic nanoparticles functionalized with spin labels as well as their interaction with yeast cells were investigated using electron spin resonance (ESR) method. ESR was demonstrated to be a suitable method for monitoring of magnetic core and attached spin labels. Particular emphasis was placed on characterization of endocytosis and redox processes running inside the cell, resulting in recombination of spin labels. Such data could only be obtained at reduced temperature of ESR measurements.

Synthesis of silver nanoparticles using a Mentha spicata extract and evaluation of its anticancer and cytotoxic activity

In this study, silver nanoparticles (NP) were synthesized by two methods: using an aqueous extract of Mentha spicata leaves and using citrate ions as stabilizing agent, and the cytotoxicity and anticancer activity of both NP were evaluated in vitro. The particles synthesized with the aqueous extract were spherical with a size ranging from 15 to 45 nm. These NP decreased cell viability in all of the cells studied; however, the IC₅₀ could only be estimated in the Chang liver cells (IC₅₀ = 21.37 µg/mL). These particles also decreased the generation of reactive oxygen species in Chang and SiHa cells. Additionally, the dispersions decreased the activity of caspase-3. There was no significant difference between the biological activities of the NP obtained with the aqueous extract and the NP synthesized using citrate ions. This study showed that an aqueous extract of M. spicata is an excellent alternative for the synthesis of silver NP. These NP showed cytotoxicity and anticancer activity in vitro. Although more experiments are required, the cell death occurs probably through a mechanism different from apoptosis.

A bio-responsive 6-mercaptopurine/doxorubicin based "Click Chemistry" polymeric prodrug for cancer therapy

A novel bio-responsive co-delivery system based on Poly(DEA)-b-Poly(ABMA-co-OEGMA) (PDPAO, prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization) copolymers was constructed for enhanced cellular internalization and effective combination therapy. Reduction-sensitive 6-mercaptopurine (6MP) based prodrug and pH-sensitive doxorubicin (DOX) based prodrug were grafted onto PDPAO by an azide-alkyne "Click Chemistry" reaction to acquire a pH/reduction-sensitive polymeric prodrug (PDPAO@imine-DOX/cis-6MP), which was able to self-aggregate to form polymeric micelles (M(DOX/6MP)) with an average particle size of 116 ± 2 nm in the water. The resultant micelles could maintain a stable sphere structure and show stability with a small particles' dispersion index in the blood. Importantly, it has been observed that the pH-sensitive surface charge-conversion accompanied pH-triggered DOX release in the biomimetic extracellular acidic environment of tumor tissue and a rapid dual-drug release triggered by pH and GSH in the intracellular environment. The in vitro evaluation of micelles on human cervical cancer (HeLa) and human promyelocytic leukemia (HL-60) cells showed an enhanced cellular uptake because of charge-conversion and exhibited a higher cell-killing performance. Moreover, the graft ratio of DOX and 6MP showed the ability to adjust the cytotoxicity; the micelles with a graft ratio of 2: 1 (M(DOX₂/6MP)) displayed the higher cellular inhibition on either HeLa (combination index (CI) = 0.62) or HL-60 (CI = 0.35) cells. Overall, this novel dual-drug-conjugated delivery system might have important potential applications for combination therapy of cancer.

A Safe-by-Design Strategy towards Safer Nanomaterials in Nanomedicines

The marriage of nanotechnology and medicine offers new opportunities to fight against human diseases. Benefiting from their unique optical, thermal, magnetic, or redox properties, a wide range of nanomaterials have shown potential in applications such as diagnosis, drug delivery, or tissue repair and regeneration. Despite the considerable success achieved over the past decades, the newly emerging nanomedicines still suffer from an incomplete understanding of their safety risks, and of the relationships between their physicochemical characteristics and safety profiles. Herein, the most important categories of nanomaterials with clinical potential and their toxicological mechanisms are summarized, and then, based on this available information, an overview of the principles in developing safe-by-design nanomaterials for medical applications and of the recent progress in this field is provided. These principles may serve as a starting point to guide the development of more effective safe-by-design strategies and to help identify the major knowledge and skill gaps.

Enhanced Chemical Stability, Intestinal Absorption, and Intracellular Antioxidant Activity of Cyanidin-3-O-glucoside by Composite Nanogel Encapsulation

A composite nanogel was developed for cyanidin-3-O-glucoside (C3G) delivery by combining Maillard reaction and heat gelation. The starting materials utilized were ovalbumin, dextran, and pectin. C3G-loaded nanogel was spherical with a diameter of ∼185 nm, which was maintained over a wide range of pH and NaCl concentrations. The composite nanogel enhanced the chemical stability of C3G under accelerated degradation models and a simulated gastrointestinal tract. Clathrin-mediated, caveolae-mediated, and macropinocytosis-related endocytosis contributed to the higher cellular uptake of nano-C3G than that of free-C3G. The apparent permeability coefficients of C3G increased 2.16 times after nanoencapsulation. The transcytosis of the C3G-bearing nanogel occurred primarily through the clathrin-related pathway and macropinocytosis and followed the "common recycling endosomes-endoplasmic reticulum-Golgi complex-basolateral plasma membrane" route. Moreover, nano-C3G was more efficient in restoring the viability of cells and activities of endogenous antioxidant enzymes than free-C3G in oxidative models, which may be attributed to the former's high cellular absorption.

Effect of interfacial serum proteins on the cell membrane disruption induced by amorphous silica nanoparticles in erythrocytes, lymphocytes, malignant melanocytes, and macrophages

It is very important to examine carefully the potential adverse effects of engineered nanoparticles (NPs) on human health and environments. In the present study, we have investigated the impact of interfacial serum proteins on the cell membrane disruption induced by silica NPs of primary diameter of 55-68 nm in four types of cells (erythrocytes, Jurkat, B16F10, and J774.1). The silica-induced membranolysis was repressed by addition of 1-2% serum into culture media, where the adhesion amount of the FBS-coated silica NPs onto a cell surface seemed comparable with that of the bare silica NPs. The nonspecific attraction between the bare silica and J774.1 cell membrane surfaces was masked by pretreatment of the silica surface with serum albumin, whereas the serum proteins-coated silica surface exhibited the attractive interactions with the cell membrane due to specific binding between some of adsorbed proteins thereon and the membrane receptors. The difference in silica-cell interaction between the nonspecific and specific attractions would explain the reason why interfacial serum proteins reduced the membranolysis without prevention of silica NPs adhering to cell surfaces.

Functionalized liposomal nanoparticles for efficient gene delivery system to neuronal cell transfection

Liposome based delivery systems provide a promising strategy for treatment of neurodegenerative diseases. A rational design of brain-targeted liposomes can support the development of more efficient treatments with drugs and gene materials. Here, we characterized surface modified liposomes with transferrin (Tf) protein and penetratin (Pen), a cell-penetrating peptide, for efficient and targeted gene delivery to brain cells. PenTf-liposomes efficiently encapsulated plasmid DNA, protected them against enzymatic degradation and exhibited a sustained in vitro release kinetics. The formulation demonstrated low cytotoxicity and was non-hemolytic. Liposomes were internalized into cells mainly through energy-dependent pathways especially clathrin-mediated endocytosis. Reporter gene transfection and consequent protein expression in different cell lines were significantly higher using PenTf-liposomes compared to unmodified liposomes. The ability of these liposomes to escape from endosomes can be an important factor which may have likely contributed to the high transfection efficiency observed. Rationally designed bifunctional targeted-liposomes provide an efficient tool for improving the targetability and efficacy of synthesized delivery systems. This investigation of liposomal properties attempted to address cell differences, as well as, vector differences, in gene transfectability. The findings indicate that PenTf-liposomes can be a safe and non-invasive approach to transfect neuronal cells through multiple endocytosis pathways.

Magnetic nanoparticles decorated with PEGylated curcumin as dual targeted drug delivery: Synthesis, toxicity and biocompatibility study

The problems associated with hydrophobic anticancer drugs are among the most important challenges to achieve efficient therapeutics for cancer treatment. In this study, PEGylated curcumin was used as the surface modification of magnetic nanoparticles (MNP@PEG-Cur) in order to simultaneously take advantage of magnetic targeting characteristic of nanoparticles and PEG conjugated drug. Curcumin was conjugated through EDC/NHS chemistry to the PEG hydroxyl functional groups, and then physically decorated on the surface of magnetic nanoparticles (MNP). The analysis of the conjugate and nanoparticles by FT-IR, ¹HNMR, FE-SEM, TEM, EDX, TGA and VSM confirmed the successful synthesis and proper physicochemical properties of MNP@PEG-Cur nanoparticles. The carrier showed pH dependent drug release profile with higher drug release at acidic media (pH = 5.4) compared to neural condition (pH = 7.4). In addition, LD₅₀ and hemolysis assay confirmed the biocompatibility of MNP@PEG-Cur. The cell viability assay also revealed that neither carrier, nor curcumin-loaded nanoparticles are cytotoxic at physiologic pH (7.4).

Spontaneous Formation of Nanoparticles from Peptide-Vinyl Polymer Diblock Hybrids Prepared by RAFT Polymerization and Their Interactions with Cells

Novel polymeric nanoparticles (NPs) with uniform sizes were prepared from peptide-vinyl polymer diblock hybrids by the self-organized precipitation method. Hybrid polymers of polystyrene (PSt) and tetrapeptide (cell-binding epitope RGDS, reverse SDGR, cationic KKKK, and anionic DDDD) were successfully synthesized by combining solid-phase peptide synthesis and reversible addition fragmentation chain transfer polymerization methods. Narrowly dispersed hybrid polymers (polydispersity index < 1.25, M _n 14 000-17 000) were obtained. Altering the preparation conditions easily tuned the size and size distribution of the NPs. When the ζ-potentials for the NP suspensions were measured at pH 6.0, the obtained values corresponded to the net charge of each peptide segment. More importantly, the NPs could encapsulate fluorescent Nile red (NR) and magnetic iron oxide NP (MNP), which might be suitable for fluorescent imaging and magnet-induced patterning of cells, respectively. The interactions of NPs with cells (NIH/3T3 fibroblast) and the magnetic effects were examined for NR/MNP-loaded PSt-RGDS and -SDGR NPs. Both NPs were readily incorporated into cells, but only NR/MNP-loaded PSt-RGDS NP showed magnetic responsiveness in cell adhesion and cultures.

High-Contrast Imaging of Nanodiamonds in Cells by Energy Filtered and Correlative Light-Electron Microscopy: Toward a Quantitative Nanoparticle-Cell Analysis

Fluorescent nanodiamonds (fNDs) represent an emerging class of nanomaterials offering great opportunities for ultrahigh resolution imaging, sensing and drug delivery applications. Their biocompatibility, exceptional chemical and consistent photostability renders them particularly attractive for correlative light-electron microscopy studies providing unique insights into nanoparticle-cell interactions. Herein, we demonstrate a stringent procedure to image and quantify fNDs with a high contrast down to the single particle level in cells. Individual fNDs were directly visualized by energy-filtered transmission electron microscopy, that is, inside newly forming, early endosomal vesicles during their cellular uptake processes as well as inside cellular organelles such as a mitochondrion. Furthermore, we demonstrate the unequivocal identification, localization, and quantification of individual fNDs in larger fND clusters inside intracellular vesicles. Our studies are of great relevance to obtain quantitative information on nanoparticle trafficking and their various interactions with cells, membranes, and organelles, which will be crucial to design-improved sensors, imaging probes, and nanotherapeutics based on quantitative data.

High-throughput 3D visualization of nanoparticles attached to the surface of red blood cells

Blood circulation is the main distribution route for systemic delivery and the possibility to manipulate red blood cells (RBCs) by attaching nanoparticles to their surface provides a great opportunity for cargo delivery into tissues. Nanocarriers attached to RBCs can be delivered to specific organs orders of magnitude faster than if injected directly into the bloodstream. Another advantage is a shielding from recognition by the immune system, thereby increasing the efficiency of delivery. We present a high-throughput microfluidic method that can monitor the shape of drifting cells due to interactions with nanoparticles and characterize the 3D dispersion of fluorescent silica nanoparticles at the surface of RBCs. The combination of fluorescence microscopy with image analysis demonstrates that the adsorption of silica nanoparticles onto the surface of RBCs is strongly influenced by electrostatic interactions. A reduced number of intact RBCs with increasing nanoparticle concentration beyond a certain threshold points to a toxicity mechanism associated with the nanoparticle adsorption at the surface of RBCs.

RGD-HK Peptide-Functionalized Gold Nanorods Emerge as Targeted Biocompatible Nanocarriers for Biomedical Applications

Gold nanorods (GNRs) have been nominated as a promising candidate for a variety of biological applications; however, the cationic surfactant layer that surrounds a nanostructure places limits on its biological applicability. Herein, CTAB-GNRs were functionalized via a ligand exchange method using a (C(HK)4-mini PEG-RGD)-peptide to target the overexpressed αvβ3 integrin in cancerous cells, increase the biocompatibility, and gain the ability of gene/drug delivery, simultaneously. To confirm an acceptable functionalization, UV-Visible, FTIR, and Raman spectroscopy, zeta potential, and transmission electron microscopy of nanostructures were done. MTT assay was applied to study the cytotoxicity of nanostructures on two cell lines, HeLa and MDA-MB-231, as positive and negative αvβ3 integrin receptors, respectively. The cytotoxic effect of peptide-functionalized GNRs (peptide-f-GNRs) was less than that of CTAB-coated GNRs (CTAB-GNRs) for both cell lines. Uptake of peptide-f-GNRs and CTAB-GNRs was evaluated in two cell lines, using dark-field imaging and atomic absorption spectroscopy. Peptide-f-GNRs showed a proper cell uptake on the HeLa rather than MDA-MB-231 cell line according to the RGD (Arg-Gly-Asp) sequence in the peptide. The ability of peptide-f-GNRs to conjugate to antisense oligonucleotides (ASO) was also confirmed using zeta potential, which was due to the repeated HK (His-Lys) sequence inside the peptide. The result of these tests highlights the functionalization method as a convenient and cost-effective strategy for promising applications of targeted GNRs in the biological gene/drug delivery systems, and the repeated histidine-lysine pattern could be a useful carrier for negatively charged drug/gene delivery, too.

A two-photon fluorophore labeled multi-functional drug carrier for targeting cancer therapy, inflammation restraint and AIE active bioimaging

Functional drug carriers with simultaneous effective delivery of therapeutic agents to target sites and great imaging ability have attracted great attention in nanomedicine research.

Extracellular Surface Potential Mapping by Scanning Ion Conductance Microscopy Revealed Transient Transmembrane Pore Formation Induced by Conjugated Polymer Nanoparticles

In-depth understanding of the biophysicochemical interactions at the nano-bio interface is important for basic cell biology and applications in nanomedicine and nanobiosensors. Here, the extracellular surface potential and topography changes of live cell membranes interacting with polymeric nanomaterials using a scanning ion conductance microscopy-based potential imaging technique are investigated. Two structurally similar amphiphilic conjugated polymer nanoparticles (CPNs) containing different functional groups (i.e., primary amine versus guanidine) are used to study incubation time and functional group-dependent extracellular surface potential and topographic changes. Transmembrane pores, which induce significant changes in potential, only appear transiently in the live cell membranes during the initial interactions. The cells are able to self-repair the damaged membrane and become resilient to prolonged CPN exposure. This study provides an important observation on how the cells interact with and respond to extracellular polymeric nanomaterials at the early stage. This study also demonstrates that extracellular surface potential imaging can provide a new insight to help understand the complicated interactions at the nano-bio interface and the following cellular responses.

Polymer nanoparticles for the intravenous delivery of anticancer drugs: the checkpoints on the road from the synthesis to clinical translation

In this review article we discuss some of the key aspects concerning the development of a polymer-based nanoparticle formulation for intravenous drug delivery. Since numerous preparations fail before and during clinical trials, our aim is to emphasize the main issues that a nanocarrier has to face once injected into the body. These include biocompatibility and toxicity, drug loading and release, nanoparticle storage and stability, biodistribution, selectivity towards the target organs or tissues, internalization in cells and biodegradability. They represent the main checkpoints to define a polymer-based formulation as safe and effective. Indeed, this review is intended to provide guidelines to be followed in the early development of a new nanotherapeutic to hopefully increase the success rate of polymer-based formulations entering clinical trials. The corresponding requirements and characteristics are discussed in the context of some relevant case studies taken from the literature and mainly related to the delivery of lipophilic anticancer therapeutics.

Tiny Rare-Earth Fluoride Nanoparticles Activate Tumour Cell Growth via Electrical Polar Interactions

Localised extracellular interactions between nanoparticles and transmembrane signal receptors may well activate cancer cell growth. Herein, tiny LaF₃ and PrF₃ nanoparticles in DMEM+FBS suspensions stimulated tumour cell growth in three different human cell lines (A549, SW837 and MCF7). Size distribution of nanoparticles, activation of AKT and ERK signalling pathways and viability tests pointed to mechanical stimulation of ligand adhesion binding sites of integrins and EGFR via a synergistic action of an ensemble of tiny size nanoparticles (< 10 nm). While tiny size nanoparticles may be well associated with the activation of EGFR, integrin interplay with nanoparticles remains a multifaceted issue. A theoretical motif shows that, within the requisite pN force scale, each ligand adhesion binding site can be activated by a tiny size dielectric nanoparticle via electrical dipole interaction. The size of the active nanoparticle stayed specified by the amount of the surface charges on the ligand adhesion binding site and the nanoparticle, and also by the separating distance between them. The polar component of the electrical dipole force remained inversely proportional to the second power of nanoparticle's size, evincing that only tiny size dielectric nanoparticles might stimulate cancer cell growth via electrical dipole interactions. The work contributes towards recognising different cytoskeletal stressing modes of cancer cells.

Cellular Signaling Pathways Activated by Functional Graphene Nanomaterials

The paper reviews the network of cellular signaling pathways activated by Functional Graphene Nanomaterials (FGN) designed as a platform for multi-targeted therapy or scaffold in tissue engineering. Cells communicate with each other through a molecular device called signalosome. It is a transient co-cluster of signal transducers and transmembrane receptors activated following the binding of transmembrane receptors to extracellular signals. Signalosomes are thus efficient and sensitive signal-responding devices that amplify incoming signals and convert them into robust responses that can be relayed from the plasma membrane to the nucleus or other target sites within the cell. The review describes the state-of-the-art biomedical applications of FGN focusing the attention on the cell/FGN interactions and signalosome activation.

Polyelectrolyte-coated ultra-small nanoparticles with Tb(III)-centered luminescence as cell labels with unusual charge effect on their cell internalization

The present work reports ultra-small polyelectrolyte-coated water insoluble Tb(III) complex species with bright Tb(III)-centered luminescence resulted from efficient ligand-to-metal energy transfer as efficient labels for Hep-2 cells. The flow cytometry data revealed the enhanced cellular uptake of negatively charged nanoparticles coated by the polystyrenesulfonate (PSS)-monolayer versus the positively charged nanoparticles. The latter are obtained by layer-by-layer deposition of polyethyleneimine (PEI) onto PSS-coated ones. Confocal and TEM images of Hep-2 cells exposed by the colloids confirm favorable cell internalization of the PSS- compared to PEI-PSS-coated colloids illustrating unusual charge-effect. Dynamic light scattering data indicate significant effect of the biological background exemplified by serum bovine albumin and phosphatidylcholine-based bilayers on the exterior charge and aggregation behavior of the colloids. The obtained results reveal the PSS-coated nanoparticles based on water insoluble Tb(III) complex as promising cell labels.

Sequentially self-assembled polysaccharide-based nanocomplexes for combined chemotherapy and photodynamic therapy of breast cancer

Combination of chemotherapy and photodynamic therapy has emerged as a promising anticancer strategy. Polysaccharide-based nanoparticles are being intensively explored as drug carriers for different forms of combination therapy. In this study, novel multifunctional polysaccharide-based nanocomplexes were prepared from aldehyde-functionalized hyaluronic acid and hydroxyethyl chitosan via sequential self-assembly method. Stable nanocomplexes were obtained through both Schiff's base bond and electrostatic interactions. Chemotherapeutics doxorubicin and pro-photosensitizer 5-aminolevulinic acid were chemically conjugated onto the nanocomplexes via Schiff base linkage. Anti-HER2 antibody as targeting moiety was decorated onto the surface of nanocomplexes. The obtained near-spherical shaped nanocomplexes had an average size of 140 nm and a zeta potential of -24.6 mV, and displayed pH-responsive surface charge reversal and drug release. Active targeting strategy significantly enhanced the cellular uptake of nanocomplexes and combined anticancer efficiency of chemo-photodynamic dual therapy in breast cancer MCF-7 cells. These results suggested that the nanocomplexes had great potential for targeted combination therapy of breast cancer.

Review of potential health risks associated with nanoscopic calcium phosphate

Calcium phosphate is applied in many products in biomedicine, but also in toothpastes and cosmetics. In some cases, it is present in nanoparticulate form, either on purpose or after degradation or mechanical abrasion. Possible concerns are related to the biological effect of such nanoparticles. A thorough literature review shows that calcium phosphate nanoparticles as such have no inherent toxicity but can lead to an increase of the intracellular calcium concentration after endosomal uptake and lysosomal degradation. However, cells are able to clear the calcium from the cytoplasm within a few hours, unless very high doses of calcium phosphate are applied. The observed cytotoxicity in some cell culture studies, mainly for unfunctionalized particles, is probably due to particle agglomeration and subsequent sedimentation onto the cell layer, leading to a very high local particle concentration, a high particle uptake, and subsequent cell death. There is no risk from an oral uptake of calcium phosphate nanoparticles due to their rapid dissolution in the stomach. The risk from dermal or mucosal uptake is very low. Calcium phosphate nanoparticles can enter the bloodstream by inhalation, but no adverse effects have been observed, except for a prolonged exposition to high particle doses. Calcium phosphate nanoparticles inside the body (e.g. after implantation or due to abrasion) do not pose a risk as they are typically resorbed and dissolved by osteoclasts and macrophages. There is no indication for a significant influence of the calcium phosphate phase or the particle shape (e.g. spherical or rod-like) on the biological response. In summary, the risk associated with an exposition to nanoparticulate calcium phosphate in doses that are usually applied in biomedicine, health care products, and cosmetics is very low and most likely not present at all.

STATEMENT OF SIGNIFICANCE

Calcium phosphate is a well-established biomaterial. However, there are occasions when it occurs in a nanoparticulate form (e.g. as nanoparticle or as nanoparticulate bone substitution material) or after abrasion from a calcium phosphate-coated metal implant. In the light of the current discussion on the safety of nanoparticles, there have been concerns about potential adverse effects of nano-calcium phosphate, e.g. in a statement of a EU study group from 2016 about possible dangers associated with non-spherical nano-hydroxyapatite in cosmetics. In the US, there was a discussion in 2016 about the dangers of nano-calcium phosphate in babyfood. In this review, the potential exposition routes for nano-calcium phosphate are reviewed, with special emphasis on its application as biomaterial.