The role of particle geometry and mechanics in the biological domain

Progress in the mechanical properties of nanoparticles for tumor-targeting delivery

Cancer nanomedicines have attracted significant attention in the past several decades, and the physicochemical properties, such as the size, shape, composition, surface charge, hydrophobicity, and mechanical properties, of nanoparticles have been optimized for potent cancer therapy. Since publishing our 2020 tutorial review "Influence of nanomedicine mechanical properties on tumor targeting delivery" in Chemical Society Reviews, substantial advancements have been made in understanding the role of mechanical properties in cancer nanomedicine. Notably, in vivo transport processes that are dependent on the mechanical properties of nanomedicine, including long circulation, tumor accumulation, and deep penetration, have been extensively studied using various nano-drug delivery systems. These studies have demonstrated that leveraging these mechanical properties can significantly enhance the antitumor efficacy of nanomedicine. In this review, we categorize the advancements in the mechanical properties of cancer nanomedicine into three distinct themes: the interactions between nanoparticles with varied mechanical properties and cells (2002 - present), the impact of these properties on in vivo delivery processes (2007 - present), and the strategic use of mechanical properties to boost cancer therapy (2023 - present). We analyze how different mechanical properties of organic, inorganic, hybrid, and biological nanoparticles affect their delivery processes at the macroscopic level, i.e., in tissues, organs and cells. At the microscopic level, their biological and physical interactions with biological barriers, physiological structures, cell membranes, organelles, and other structures reveal the potential mechanism of nanoparticles' mechanical properties in determining their antitumor efficacy. Furthermore, we address the current challenges and future prospects in the mechanical properties of cancer nanomedicine, as well as the clinical translation potential of nanoparticles with diverse mechanical characteristics.

Regulation of Cell-Nanoparticle Interactions through Mechanobiology

Bio-nano interactions have been extensively explored in nanomedicine to develop selective delivery strategies and reduce systemic toxicity. To enhance the delivery of nanocarriers to cancer cells and improve the therapeutic efficiency, different nanomaterials have been developed. However, the limited clinical translation of nanoparticle-based therapies, largely due to issues associated with poor targeting, requires a deeper understanding of the biological phenomena underlying cell-nanoparticle interactions. In this context, we investigate the molecular and cellular mechanobiology parameters that control such interactions. We demonstrate that the pharmacological inhibition or the genetic ablation of the key mechanosensitive component of the Hippo pathway, i.e., yes-associated protein, enhances nanoparticle internalization by 1.5-fold. Importantly, this phenomenon occurs independently of nanoparticle properties, such as size, or cell properties such as surface area and stiffness. Our study reveals that the internalization of nanoparticles in target cells can be controlled by modulating cell mechanosensing pathways, potentially enhancing nanotherapy specificity.

A Review on Investigating the Interactions between Nanoparticles and the Pulmonary Surfactant Monolayer with Coarse-Grained Molecular Dynamics Method

Pulmonary drug delivery has garnered significant attention due to its targeted local lung action, minimal toxic side effects, and high drug utilization. However, the physicochemical properties of inhaled nanoparticles (NPs) used as drug carriers can influence their interactions with the pulmonary surfactant (PS) monolayer, potentially altering the fate of the NPs and impairing the biophysical function of the PS monolayer. Thus, the objective of this review is to summarize how the physicochemical properties of NPs affect their interactions with the PS monolayer. Initially, the definition and properties of NPs, as well as the composition and characteristics of the PS monolayer, are introduced. Subsequently, the coarse-grained molecular dynamics (CGMD) simulation method for studying the interactions between NPs and the PS monolayer is presented. Finally, the implications of the hydrophobicity, size, shape, surface charge, surface modification, and aggregation of NPs on their interactions with the PS monolayer and on the composition of biomolecular corona are discussed. In conclusion, gaining a deeper understanding of the effects of the physicochemical properties of NPs on their interactions with the PS monolayer will contribute to the development of safer and more effective nanomedicines for pulmonary drug delivery.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

YAP Signaling Regulates the Cellular Uptake and Therapeutic Effect of Nanoparticles

Interactions between living cells and nanoparticles are extensively studied to enhance the delivery of therapeutics. Nanoparticles size, shape, stiffness, and surface charge are regarded as the main features able to control the fate of cell-nanoparticle interactions. However, the clinical translation of nanotherapies has so far been limited, and there is a need to better understand the biology of cell-nanoparticle interactions. This study investigates the role of cellular mechanosensitive components in cell-nanoparticle interactions. It is demonstrated that the genetic and pharmacologic inhibition of yes-associated protein (YAP), a key component of cancer cell mechanosensing apparatus and Hippo pathway effector, improves nanoparticle internalization in triple-negative breast cancer cells regardless of nanoparticle properties or substrate characteristics. This process occurs through YAP-dependent regulation of endocytic pathways, cell mechanics, and membrane organization. Hence, the study proposes targeting YAP may sensitize triple-negative breast cancer cells to chemotherapy and increase the selectivity of nanotherapy.

Recent Advances in Targeted Drug Delivery Strategy for Enhancing Oncotherapy

Targeted drug delivery is a precise and effective strategy in oncotherapy that can accurately deliver drugs to tumor cells or tissues to enhance their therapeutic effect and, meanwhile, weaken their undesirable side effects on normal cells or tissues. In this research field, a large number of researchers have achieved significant breakthroughs and advances in oncotherapy. Typically, nanocarriers as a promising drug delivery strategy can effectively deliver drugs to the tumor site through enhanced permeability and retention (EPR) effect-mediated passive targeting and various types of receptor-mediated active targeting, respectively. Herein, we review recent targeted drug delivery strategies and technologies for enhancing oncotherapy. In addition, we also review two mainstream drug delivery strategies, passive and active targeting, based on various nanocarriers for enhancing tumor therapy. Meanwhile, a comparison and combination of passive and active targeting are also carried out. Furthermore, we discuss the associated challenges of passive and active targeted drug delivery strategies and the prospects for further study.

Co-Polymer Carrier with Dual Advantages of Cartilage-Penetrating and Targeting Improves Delivery and Efficacy of MicroRNA Treatment of Osteoarthritis

Osteoarthritis (OA) is a debilitating joint disease affecting nearly 400 million people with no efficient etiological therapies. OA is primarily identified by cartilage destruction, and gradual degeneration of the whole joint would happen when the OA progresses. Hence, cartilage has been identified as the primary therapeutic target of OA. Unfortunately, numerous barriers block the delivery of therapeutic agents into cartilage, including avascular traits and high hardness of the extracellular matrix. Herein, a cartilage-targeting peptide (CAP) modified polyvinylamine (PVAm)- poly (lactic-co-glycolic acid) (PLGA) copolymer (CAP-PVAm-PLGA) is designed, which can form spherical nanoparticles with the r-miR-140 (CPP-NPs). CPP-NPs possessed enhanced mechanical properties due to the introduction of PLGA to vehicles. Meanwhile, CAP endowed the cartilage targeting which facilitated CPP-NPs localization in cartilage. With such dual advantages, CPP-NPs exhibited outstanding penetrability and accumulation in cartilage even subchondral bone, and can penetrate to a depth of 1000 µm into human cartilage. The degeneration area of cartilage is reduced by 65% and synovial inflammation score by 80% in OA mice, and the microarchitecture of subchondral bone is also ameliorated. These studies established a promising platform for therapeutic RNA delivery in OA therapy that overcame the cartilage barriers.

Polymeric Nanoparticles for Inhaled Vaccines

Many recent studies focus on the pulmonary delivery of vaccines as it is needle-free, safe, and effective. Inhaled vaccines enhance systemic and mucosal immunization but still faces many limitations that can be resolved using polymeric nanoparticles (PNPs). This review focuses on the use of properties of PNPs, specifically chitosan and PLGA to be used in the delivery of vaccines by inhalation. It also aims to highlight that PNPs have adjuvant properties by themselves that induce cellular and humeral immunogenicity. Further, different factors influence the behavior of PNP in vivo such as size, morphology, and charge are discussed. Finally, some of the primary challenges facing PNPs are reviewed including formulation instability, reproducibility, device-related factors, patient-related factors, and industrial-level scale-up. Herein, the most important variables of PNPs that shall be defined in any PNPs to be used for pulmonary delivery are defined. Further, this study focuses on the most popular polymers used for this purpose.

Effect of the stiffness of one-layer protein-based microcapsules on dendritic cell uptake and endocytic mechanism

Microcapsules are one of the most promising microscale drug carriers due to their facile fabrication, excellent deformability, and high efficacy in drug storage and delivery. Understanding the effects of their physicochemical properties (size, shape, rigidity, charge, surface chemistry, etc.) on both in vitro and in vivo performance is not only highly significant and interesting but also very challenging. Stiffness, an important design parameter, has been extensively explored in recent years, but how the rigidity of particles influences cellular internalization and uptake mechanisms remains controversial. Here, one-layered lysozyme-based microcapsules with well-controlled stiffness (modulus ranging from 3.49 ± 0.18 MPa to 26.14 ± 1.09 MPa) were prepared and used to investigate the effect of stiffness on the uptake process in dendritic cells and the underlying mechanism. The cellular uptake process and endocytic mechanism were investigated with laser scanning confocal microscopy, mechanism inhibitors, and pathway-specific antibody staining. Our data demonstrated that the stiffness of protein-based microcapsules could be a strong regulator of intracellular uptake and endocytic kinetics but had no obvious effect on the endocytic mechanism. We believe our results will provide a basic understanding of the intracellular uptake process of microcapsules and the endocytic mechanism and inspire strategies for the further design of potential drug delivery microcarriers.

Physiologically Relevant Mechanics of Biodegradable Polyester Nanoparticles

Despite the extensive use of biodegradable polyester nanoparticles for drug delivery, and reports of the strong influence of nanoparticle mechanics on nano-bio interactions, there is a lack of systematic studies on the mechanics of these nanoparticles under physiologically relevant conditions. Here, we report indentation experiments on poly(lactic acid) and poly(lactide-co-glycolide) nanoparticles using atomic force microscopy. While dried nanoparticles were found to be rigid at room temperature, their elastic modulus was found to decrease by as much as 30 fold under simulated physiological conditions (i.e., in water at 37 °C). Differential scanning calorimetry confirms that this softening can be attributed to the glass transition of the nanoparticles. Using a combination of mechanical and thermoanalytical characterization, the plasticizing effects of miniaturization, molecular weight, and immersion in water were investigated. Collectively, these experiments provide insight for experimentalists exploring the relationship between polymer nanoparticle mechanics and in vivo behavior.

Effect of elasticity on the phagocytosis of micro/nanoparticles

A broad range of investigation methods and frameworks are used to better study the elasticity of various micro/nanoparticles (MNPs) with different properties and to explore the effect of such properties on their interactions with biological species.

Thermodynamic analysis of multivalent binding of functionalized nanoparticles to membrane surface reveals the importance of membrane entropy and nanoparticle entropy in adhesion of flexible nanoparticles

We present a quantitative model for multivalent binding of ligand-coated flexible polymeric nanoparticles (NPs) to a flexible membrane expressing receptors. The model is developed using a multiscale computational framework by coupling a continuum field model for the cell membrane with a coarse-grained model for the polymeric NPs. The NP is modeled as a self-avoiding bead-spring polymer chain, and the cell membrane is modeled as a triangulated surface using the dynamically triangulated Monte Carlo method. The nanoparticle binding affinity to a cell surface is mainly determined by the delicate balance between the enthalpic gain due to the multivalent ligand-receptor binding and the entropic penalties of various components including receptor translation, membrane undulation, and NP conformation. We have developed new methods to compute the free energy of binding, which includes these enthalpy and entropy terms. We show that the multivalent interactions between the flexible NP and the cell surface are subject to entropy-enthalpy compensation. Three different entropy contributions, namely, those due to receptor-ligand translation, NP flexibility, and membrane undulations, are all significant, although the first of these terms is the most dominant. However, both NP flexibility and membrane undulations dictate the receptor-ligand translational entropy making the entropy compensation context-specific, i.e., dependent on whether the NP is rigid or flexible, and on the state of the membrane given by the value of membrane tension or its excess area.

The Hemocompatibility of Nanoparticles: A Review of Cell-Nanoparticle Interactions and Hemostasis

Understanding cell-nanoparticle interactions is critical to developing effective nanosized drug delivery systems. Nanoparticles have already advanced the treatment of several challenging conditions including cancer and human immunodeficiency virus (HIV), yet still hold the potential to improve drug delivery to elusive target sites. Even though most nanoparticles will encounter blood at a certain stage of their transport through the body, the interactions between nanoparticles and blood cells is still poorly understood and the importance of evaluating nanoparticle hemocompatibility is vastly understated. In contrast to most review articles that look at the interference of nanoparticles with the intricate coagulation cascade, this review will explore nanoparticle hemocompatibility from a cellular angle. The most important functions of the three cellular components of blood, namely erythrocytes, platelets and leukocytes, in hemostasis are highlighted. The potential deleterious effects that nanoparticles can have on these cells are discussed and insight is provided into some of the complex mechanisms involved in nanoparticle-blood cell interactions. Throughout the review, emphasis is placed on the importance of undertaking thorough, all-inclusive hemocompatibility studies on newly engineered nanoparticles to facilitate their translation into clinical application.

Nanoparticle Optimization for Enhanced Targeted Anticancer Drug Delivery

Nanoparticle (NP)-based drug delivery is a promising method to increase the therapeutic index of anticancer agents with low median toxic dose. The delivery efficiency, corresponding to the fraction of the injected NPs that adhere to the tumor site, depends on NP size a and aspect ratio AR. Values for these variables are currently chosen empirically, which may not result in optimal targeted drug delivery. This study applies rigorous optimization to the design of NPs. A preliminary investigation revealed that delivery efficiency increases monotonically with a and AR. However, maximizing a and AR results in nonuniform drug distribution, which impairs tumor regression. Therefore, a multiobjective optimization (MO) problem is formulated to quantify the trade-off between NPs accumulation and distribution. The MO is solved using the derivative-free mesh adaptive direct search algorithm. Theoretically, the Pareto-optimal set consists of an infinite number of mathematically equivalent solutions to the MO problem. However, interesting design solutions can be identified subjectively, e.g., the ellipsoid with a major axis of 720 nm and an aspect ratio of 7.45, as the solution closest to the utopia point. The MO problem formulation is then extended to optimize NP biochemical properties: ligand-receptor binding affinity and ligand density. Optimizing physical and chemical properties simultaneously results in optimal designs with reduced NP sizes and thus enhanced cellular uptake. The presented study provides an insight into NP structures that have potential for producing desirable drug delivery.

Chain-Length- and Saturation-Tuned Mechanics of Fluid Nanovesicles Direct Tumor Delivery

Small unilamellar vesicles (SUVs), ubiquitous in organisms, play key and active roles in various biological processes. Although the physical properties of the constituent lipid molecules (i.e., the acyl chain length and saturation) are known to affect the mechanical properties of SUVs and consequently regulate their biological behaviors and functions, the underlying mechanism remains elusive. Here, we combined theoretical modeling and experimental investigation to probe the mechanical behaviors of SUVs with different lipid compositions. The membrane bending rigidity of SUVs increased with increasing chain length and saturation, resulting in differences in the vesicle rigidity and deformable capacity. Furthermore, we tested the tumor delivery capacity of liposomes with low, intermediate, and high rigidity as typical models for SUVs. Interestingly, liposomes with intermediate rigidity exhibited better tumor extracellular matrix diffusion and multicellular spheroid (MCS) penetration and retention than that of their stiffer or softer counterparts, contributing to improved tumor suppression. Stiff SUVs had superior cellular internalization capacity but intermediate tumor delivery efficacy. Stimulated emission depletion microscopy directly showed that the optimal formulation was able to transform to a rod-like shape in MCSs, which stimulated fast transport in tumor tissues. In contrast, stiff liposomes hardly deformed, whereas soft liposomes changed their shape irregularly, which slowed their MCS penetration. Our findings introduce special perspectives from which to map the detailed mechanical properties of SUVs with different compositions, provide clues for understanding the biological functions of SUVs, and suggest that liposome mechanics may be a design parameter for enhancing drug delivery.

Cellular internalization of polypeptide-based nanoparticles: effects of size, shape and surface morphology

Nanoparticles (NPs) can be taken up by cells; however, the effects of the structural characteristics of NPs on their cellular internalization have not been well explored. In this work, cellular internalization performances of various NPs including rods with helical surface (helical rods), spheres with stripe-pattern surface (striped spheres), and spheres with smooth surface (smooth spheres) were investigated by a combination of experiments and theoretical simulations. This study focuses on the effects of the size, shape, and surface morphology on their cellular internalization behaviors. These NPs were self-assembled from mixtures of fluorescein isothiocyanate (FITC)-labelled poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG(FITC)-b-PEG) block copolymers and PBLG or polystyrene (PS) homopolymers. It was found that the NPs possessing smaller size, rod-like shape, and helical/striped surface morphology exhibit higher cellular internalization efficiency. Such differences in the internalization efficiency for the NPs can be attributed to the differences in both their surface areas and internalization pathways. This study could not only guide the design of nanocarriers with enhanced cellular internalization efficiency, but also deepen our understanding of the internalization behavior of natural NPs with similar structures (e.g., virus).

Shape-Dependent Biodistribution of Biocompatible Silk Microcapsules

Microcapsules are emerging as promising microsize drug carriers due to their remarkable deformability. Shape plays a dominant role in determining their vascular transportation. Herein, we explored the effect of the shape of the microcapsules on the in vivo biodistribution for rational design of microcapsules to achieve optimized targeting efficiency. Silk fibroin, a biocompatible, biodegradable, and abundant material, was utilized as a building block to construct biconcave discoidal and spherical microcapsules with diameter of 1.8 μm and wall thickness of 20 nm. We have compared the cytocompatibility, cellular uptake, and biodistribution of both microcapsules. Both biconcave and spherical microcapsules exhibited excellent cytocompatibility and internalization into cancer cells. During blood circulation in mice, both microcapsules showed retention in liver and kidney and most underwent renal clearance. However, we observed significantly higher accumulation of biconcave silk microcapsules in lung compared with spherical microcapsules, and the accumulation was found to be stable in lung even after 3 days. The higher concentration of biconcave discoidal microcapsules found in lung arises from pulmonary environment, margination dynamics, and enhanced deformation in bloodstream. Red blood cell (RBC)-mimicking silk microcapsules demonstrated here can potentially serve as a promising platform for delivering drugs for lung diseases.

Integration of hyper-compliant microparticles into a 3D melanoma tumor model

Multicellular spheroids provide a physiologically relevant platform to study the microenvironment of tumors and therapeutic applications, such as microparticle-based drug delivery. The goal of this study was to investigate the incorporation/penetration of compliant polyacrylamide microparticles (MPs), into either cancer or normal human cell spheroids. Incorporation of collagen-1-coated MPs (stiffness: 0.1 and 9 kPa; diameter: 15-30 µm) into spheroids (diameter ∼100 µm) was tracked for up to 22 h. Results indicated that cells within melanoma spheroids were more influenced by MP mechanical properties than cells within normal cell spheroids. Melanoma spheroids had a greater propensity to incorporate and displace the more compliant MPs over time. Mature spheroids composed of either cell type were able to recognize and integrate MPs. While many tumor models exist to study drug delivery and efficacy, the study of uptake and incorporation of cell-sized MPs into established spheroids/tissues or tumors has been limited. The ability of hyper-compliant MPs to successfully penetrate 3D tumor models with natural extracellular matrix deposition provides a novel platform for potential delivery of drugs and other therapeutics into the core of tumors and micrometastases.

Recent and prominent examples of nano- and microarchitectures as hemoglobin-based oxygen carriers

Blood transfusions, which usually consist in the administration of isolated red blood cells (RBCs), are crucial in traumatic injuries, pre-surgical conditions and anemias. Although RBCs transfusion from donors is a safe procedure, donor RBCs can only be stored for a maximum of 42 days under refrigerated conditions and, therefore, stockpiles of RBCs for use in acute disasters do not exist. With a worldwide shortage of donor blood that is expected to increase over time, the creation of oxygen-carriers with long storage life and compatibility without typing and cross-matching, persists as one of the foremost important challenges in biomedicine. However, research has so far failed to produce FDA approved RBCs substitutes (RBCSs) for human usage. As such, due to unacceptable toxicities, the first generation of oxygen-carriers has been withdrawn from the market. Being hemoglobin (Hb) the main component of RBCs, a lot of effort is being devoted in assembling semi-synthetic RBCS utilizing Hb as the oxygen-carrier component, the so-called Hb-based oxygen carriers (HBOCs). However, a native RBC also contains a multi-enzyme system to prevent the conversion of Hb into non-functional methemoglobin (metHb). Thus, the challenge for the fabrication of next-generation HBOCs relies in creating a system that takes advantage of the excellent oxygen-carrying capabilities of Hb, while preserving the redox environment of native RBCs that prevents or reverts the conversion of Hb into metHb. In this review, we feature the most recent advances in the assembly of the new generation of HBOCs with emphasis in two main approaches: the chemical modification of Hb either by cross-linking strategies or by conjugation to other polymers, and the Hb encapsulation strategies, usually in the form of lipidic or polymeric capsules. The applications of the aforementioned HBOCs as blood substitutes or for oxygen-delivery in tissue engineering are highlighted, followed by a discussion of successes, challenges and future trends in this field.

Shear rate dependent margination of sphere-like, oblate-like and prolate-like micro-particles within blood flow

This study investigates the shear rate dependent margination of micro-particles (MPs) with different shapes in blood flow through numerical simulations. We develop a multiscale computational model to handle the fluid-structure interactions involved in the blood flow simulations. The lattice Boltzmann method (LBM) is used to solve the plasma dynamics and a coarse-grained model is employed to capture the dynamics of red blood cells (RBCs) and MPs. These two solvers are coupled together by the immersed boundary method (IBM). The shear rate dependent margination of sphere MPs is firstly investigated. We find that margination of sphere MPs dramatically increases with the increment of wall shear rate [small gamma, Greek, dot above]ω under 800 s-1, induced by the breaking of rouleaux in blood flow. However, the margination probability only slowly grows when [small gamma, Greek, dot above]ω > 800 s-1. Furthermore, the shape effect of MPs is examined by comparing the margination behaviors of sphere-like, oblate-like and prolate-like MPs under different wall shear rates. We find that the margination of MPs is governed by the interplay of two factors: hydrodynamic collisions with RBCs including the collision frequency and collision displacement of MPs, and near wall dynamics. MPs that demonstrate poor performance in one process such as collision frequency may stand out in the other process like near wall dynamics. Specifically, the ellipsoidal MPs (oblate and prolate) with small aspect ratio (AR) outperform those with large AR regardless of the wall shear rate, due to their better performance in both the collision with RBCs and near wall dynamics. Additionally, we find there exists a transition shear rate region 700 s-1 < [small gamma, Greek, dot above]ω < 900 s-1 for all of these MPs: the margination probability dramatically increases with the shear rate below this region and slowly grows above this region, similar to sphere MPs. We further use the surface area to volume ratio (SVR) to distinguish different shaped MPs and illustrate their shear rate dependent margination in a contour in the shear rate-SVR plane. It is of significance that we can approximately predict the margination of MPs with a specific SVR. All these simulation results can be potentially applied to guide the design of micro-drug carriers for biomedical applications.

Facile production of nanocomposites of carbon nanotubes and polycaprolactone with high aspect ratios with potential applications in drug delivery

The geometries and surface properties of nanocarriers greatly influence the interaction between nanomaterials and living cells. In this work we combine multiwalled carbon nanotubes (CNTs) with poly-ε-caprolactone (PCL) to produce non-spherical nanocomposites with high aspect ratios by using a facile emulsion solvent evaporation method. Particles were characterised by dynamic light scattering (DLS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and asymmetric flow field flow fractionation (AF4). Different sizes and morphologies of nanoparticles were produced depending on the concentration of the sodium dodecyl sulphate (SDS), CNTs and PCL. Rod-like PCL-CNT nanostructures with low polydispersity were obtained with 1.5 mg mL-1 of SDS, 0.9 mg mL-1 of CNTs and 10 mg mL-1 PCL. AFM analysis revealed that the PCL and PCL-CNT nanocomposite had comparatively similar moduli of 770 and 560 MPa respectively, indicating that all the CNTs have been coated with at least 2 nm of PCL. Thermogravimetric analysis of the PCL-CNT nanocomposite indicated that they contained 9.6% CNTs by mass. The asymmetric flow field flow fractionation of the samples revealed that the PCL-CNT had larger hydrodynamic diameters than PCL alone. Finally, the drug loading properties of the nanocomposites were assessed using docetaxel as the active substance. The nanocomposites showed comparable entrapment efficiencies of docetaxel (89%) to the CNTs alone (95%) and the PCL nanoparticles alone (81%). This is a facile method for obtaining non-spherical nanocomposites that combines the properties of PCL and CNTs such as the high aspect ratio, modulus. The high drug entrapment efficiency of these nanocomposites may have promising applications in drug delivery.

Study on the formation and properties of red blood cell-like Fe3O4/TbLa3(Bim)12/PLGA composite particles

Besides the particle size and surface performance, the shape also plays a key role in drug delivery systems. Red blood cells are the most abundant blood cells in the human body, and are excellent oxygen carriers, due to their unique biconcave discoid shape. In this study, red blood cell (RBC)-like Fe3O4/TbLa3(Bim)12/poly(lactic-co-glycolic acid) (PLGA) composite particles, with magnetic response and bioimaging functions, were prepared by electrospraying. Various electrospraying parameters, such as solvent, PLGA concentration, collecting distance and solution flow rate were investigated in detail to attempt to obtain RBC-like composite particles. The size distribution, morphology, structure, and hydrophobicity-hydrophilicity of particles were characterized. The results revealed the RBC-like Fe3O4/TbLa3(Bim)12/PLGA composite particles exhibited a strong green fluorescence and good magnetic behavior even when incubated with cells. Furthermore, the intensity of the magnetization and fluorescence can be adjusted by changing the contents of Fe3O4 and TbLa3(Bim)12. The effect on cell viability of the RBC-like Fe3O4/TbLa3(Bim)12/PLGA composite particles was evaluated in A549 cells and RBCs, and it was determined to have low cytotoxicity and excellent blood biocompatibility, suggesting that it is a promising candidate for application in drug delivery, targeting and tracking.

Understanding the Effects of Nanocapsular Mechanical Property on Passive and Active Tumor Targeting

The physicochemical properties of nanoparticles (size, charge, and surface chemistry, etc.) influence their biological functions often in complex and poorly understood ways. This complexity is compounded when the nanostructures involved have variable mechanical properties. Here, we report the synthesis of liquid-filled silica nanocapsules (SNCs, ∼ 150 nm) having a wide range of stiffness (with Young's moduli ranging from 704 kPa to 9.7 GPa). We demonstrate a complex trade-off between nanoparticle stiffness and the efficiencies of both immune evasion and passive/active tumor targeting. Soft SNCs showed 3 times less uptake by macrophages than stiff SNCs, while the uptake of PEGylated SNCs by cancer cells was independent of stiffness. In addition, the functionalization of stiff SNCs with folic acid significantly enhanced their receptor-mediated cellular uptake, whereas little improvement for the soft SNCs was conferred. Further in vivo experiments confirmed these findings and demonstrated the critical role of nanoparticle mechanical properties in regulating their interactions with biological systems.

Effect of internal architecture on microgel deformation in microfluidic constrictions

The study of how soft particles deform to pass through narrow openings is important for understanding the transit of biological cells, as well as for designing deformable drug delivery carriers. In this work, we systematically explore how soft microparticles with various internal architectures deform during passage through microfluidic constrictions. We synthesize hydrogel particles with well-defined internal structure using lithography-based UV polymerization in microfluidic channels (stop-flow lithography). Using this in situ technique, we explore a range of 2D particle architectures and their effect on particle deformation. We observe that particles undergo buckling of internal supports and reorient at the constriction entrance in order to adopt preferred shapes that correspond to minimum energy configurations. Using finite element simulations of elastic deformation under compression, we accurately predict the optimal deformation configuration of these structured particles.

Improved Targeting of Cancers with Nanotherapeutics

Targeted cancer nanotherapeutics offers numerous opportunities for the selective uptake of toxic chemotherapies within tumors and cancer cells. The unique properties of nanoparticles, such as their small size, large surface-to-volume ratios, and the ability to achieve multivalency of targeting ligands on their surface, provide superior advantages for nanoparticle-based drug delivery to a variety of cancers. This review highlights various key concepts in the design of targeted nanotherapeutics for cancer therapy, and discusses physicochemical parameters affecting nanoparticle targeting, along with recent developments for cancer-targeted nanomedicines.

Impact of particle elasticity on particle-based drug delivery systems

Modification of nano/micro-particle physical parameters (e.g. size, shape, surface charge) has proven to be an effective method to enhance their delivery abilities. Recently, advances in particle synthesis have facilitated investigations into the role that particle elasticity plays in modulating drug delivery processes. This review will highlight: (i) methods to tune particle elasticity, (ii) the role particle elasticity plays in cellular internalization, (iii) the role of particle elasticity in modulating circulation times, (iv) the effect of particle elasticity on altering biodistribution and tissue targeting, and (v) the application of computational methods to explain the differences in cellular internalization of particles of different elasticities. Overall, literature reports suggest a complex relationship between particle elasticity and drug delivery processes. Despite this complex relationship, it is clear from numerous in vitro and in vivo studies that particle elasticity is an important parameter that can be leveraged to improve blood circulation, tissue targeting, and specific interactions with cells.

Superparamagnetic anisotropic nano-assemblies with longer blood circulation in vivo: a highly efficient drug delivery carrier for leukemia therapy

Leukemia, unlike solid tumors, has no definite shape and spreads throughout the whole circulatory system, therefore the therapy of leukemia requires medication to stay longer in the circulatory system. Anisotropic nanoparticles, showing longer blood circulating life than that of isotropic nanoparticles reported in previous research, meet the demands of leukemia therapy. Based on this strategy, superparamagnetic anisotropic nano-assemblies (SANs) were fabricated and loaded with vincristine (VCR) to form VCR-SANs. When compared to the same dose of VCR-loaded isotropic nano-assemblies (SINs), the decrease in the leukocytes count and the positive expression ratio of CD13 in the VCR-SANs group were 19.38% and 16.4%, respectively, which indicated the improved anti-leukemia activity of the VCR-SANs. From the results of the pharmacokinetics study, the VCR-SANs remarkably held the amount of drug removed from the whole body per unit time half of the isotropic group and the concentration of drug in blood plasma against time was 2.1 times the isotropic group, demonstrating the rapid and sustained release behavior and longer blood circulation when combined with the results of in vivo tissue distribution studies. In summary, anisotropic nano-assemblies were found to be more promising than isotropic nano-assemblies via our in vivo and in vitro examinations.

Probing cell internalisation mechanics with polymer capsules

We report polymer capsule-based probes for quantifying the pressure exerted by cells during capsule internalisation (P_in). Poly(methacrylic acid) (PMA) capsules with tuneable mechanical properties were fabricated through layer-by-layer assembly. The P_in was quantified by correlating the cell-induced deformation with the ex situ osmotically induced deformation of the polymer capsules. Ultimately, we found that human monocyte-derived macrophage THP-1 cells exerted up to approximately 360 kPa on the capsules during internalisation.

Non-spherical particle generation from 4D optofluidic fabrication

Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles.

Nanometric emulsions encapsulating solid particles as alternative carriers for intracellular delivery

AIM

Formulate nanometric oil droplets for encapsulating solid nanoparticles and assess their interactions with cells.

MATERIALS & METHODS

Soybean oil droplets, stabilized by Pluronic F68 surfactant, incorporating hydrophobically modified fluorescent silica, nanoparticles were obtained. Cytotoxicity over time, internalization, subsequent intracellular localization and internalization pathways were assessed by microscopy (fluoresence and TEM) in vitro with HeLa cells.

RESULTS

Oil droplets encapsulating solid nanoparticles are readily internalized by HeLa cells like free nanoparticles but the intracellular localization differs (nanoemulsions less colocalized with lysosomes) as well as internalization pathway is used (nanoemulsions partially internalized by nonendocytic transport). No cytotoxicity could be observed for either particles tested.

CONCLUSION

Our results confirm that nanometric emulsions encapsulating solid nanoparticles can be used for alternative and multifunctional intracellular delivery.

Flexible Octopus-Shaped Hydrogel Particles for Specific Cell Capture

Multiarm hydrogel microparticles with varying geometry are fabricated to specifically capture cells expressing epithelial cell adhesion molecule. Results show that particle shape influences cell-capture efficiency due to differences in surface area, hydrodynamic effects, and steric constraints. These findings can lead to improved particle design for cell separation and diagnostic applications.

Stable non-covalent labeling of layered silicate nanoparticles for biological imaging

Layered silicate nanoparticles (LSN) are widely used in industrial applications and consumer products. They also have potential benefits in biomedical applications such as implantable devices and for drug delivery. To study how nanomaterials interact with cells and tissues, techniques to track and quantify their movement through different biological compartments are essential. While radiolabels can be very sensitive, particularly for in vivo studies, fluorescent labeling has been preferred in recent years because of the array of methods available to image and quantify fluorescent nanoparticles. However, labeling can be problematic, especially if it alters the physical properties of the nanomaterial. Herein is described a novel non-covalent labeling technique for LSN using readily available fluorescent dimeric cyanine dyes without the need to use excess amounts of dye to achieve labeling, or the need for removal of unbound dye. The approach utilizes the cationic binding properties of layered silicate clays and the multiple quaternary nitrogens associated with the dyes. Preparation of YOYO-1 labeled LSN with optimal dispersion in aqueous media is presented. The utilization of the labeled particles is then demonstrated in cell binding and uptake studies using flow cytometry and confocal microscopy. The labeled LSN are highly fluorescent, stable and exhibit identical physical properties with respect to the unlabeled nanoparticles. The general approach described here is applicable to other cyanine dyes and may be utilized more widely for labeling nanoparticles that comprise a crystalline plate structure with a high binding capacity.

Biomimetic Concealing of PLGA Microspheres in a 3D Scaffold to Prevent Macrophage Uptake

Scaffolds functionalized with delivery systems for the release of growth factors is a robust strategy to enhance tissue regeneration. However, after implantation, macrophages infiltrate the scaffold, eventually initiating the degradation and clearance of the delivery systems. Herein, it is hypothesized that fully embedding the poly(d,l-lactide-co-glycolide acid) microspheres (MS) in a highly structured collagen-based scaffold (concealing) can prevent their detection, preserving the integrity of the payload. Confocal laser microscopy reveals that non-embedded MS are easily internalized; when concealed, J774 and bone marrow-derived macrophages (BMDM) cannot detect them. This is further demonstrated by flow cytometry, as a tenfold decrease is found in the number of MS engulfed by the cells, suggesting that collagen can cloak the MS. This correlates with the amount of nitric oxide and tumor necrosis factor-α produced by J774 and BMDM in response to the concealed MS, comparable to that found for non-functionalized collagen scaffolds. Finally, the release kinetics of a reporter protein is preserved in the presence of macrophages, only when MS are concealed. The data provide detailed strategies for fabricating three dimensional (3D) biomimetic scaffolds able to conceal delivery systems and preserve the therapeutic molecules for release.

Passive tumour targeting and extravasation of cylindrical polymer brushes in mouse xenografts

The passive tumour targeting and extravasation performance of PEGMA-based cylindrical polymer brushes was investigated, including their behaviour upon changes to their aspect ratio.

Structure Governs the Deformability of Polymer Particles in a Microfluidic Blood Capillary Model

Particle stiffness is a design parameter that affects bionano interactions, including biodistribution kinetics and cellular processing. Herein, we develop soft polysaccharide (hyaluronic acid, HA) replica particles and capsules with tunable stiffness and sizes similar to human red blood cells (RBCs) via atom transfer radical polymerization-mediated continuous assembly of polymers (CAP_ATRP) and investigate their stiffness and deformability using colloidal-probe atomic force microscopy (CP-AFM) and a microfluidic blood capillary model, respectively. We demonstrate that HA replica particles and capsules with comparable nanoscale stiffness exhibit significantly different behaviors in a microfluidic blood capillary model. HA capsules behaved as RBCs, while HA replica particles had difficulty passing through the capillaries. These results (i) demonstrate how flow-based deformability measurements can be used to complement nanoscale stiffness measurements and (ii) provide important insight into the role of particle structure on the flow-based deformability of soft replica particles and capsules in a physiologically relevant microfluidic model.

Modular Vaccine Design Using Carrier-Free Capsules Assembled from Polyionic Immune Signals

New vaccine adjuvants that direct immune cells toward specific fates could support more potent and selective options for diseases spanning infection to cancer. However, the empirical nature of vaccines and the complexity of many formulations has hindered design of well-defined and easily characterized vaccines. We hypothesized that nanostructured capsules assembled entirely from polyionic immune signals might support a platform for simple, modular vaccines. These immune-polyelectrolyte (iPEM) capsules offer a high signal density, selectively expand T cells in mice, and drive functional responses during tumor challenge. iPEMs incorporating clinically relevant antigens could improve vaccine definition and support more programmable control over immunity.

Synthesis of Nonspherical Microcapsules through Controlled Polyelectrolyte Coating of Hydrogel Templates

We report a simple approach to fabricate custom-shape microcapsules using hydrogel templates synthesized by stop flow lithography. Cargo-containing microcapsules were made by coating hydrogel particles with a single layer of poly-l-lysine followed by a one-step core degradation and capsule cross-linking procedure. We determined appropriate coating conditions by investigating the effect of pH, ionic strength, and prepolymer composition on the diffusion of polyelectrolytes into the oppositely charged hydrogel template. We also characterized the degradation of the templating core by tracking the diffusivity of nanoparticles embedded within the hydrogel. Unlike any other technique, this approach allows for easy fabrication of microcapsules with internal features (e.g., toroids) and selective surface modification of Janus particles using any polyelectrolyte. These soft, flexible capsules may be useful for therapeutic applications as well as fundamental studies of membrane mechanics.

A method to tune the shape of protein-encapsulated polymeric microspheres

Protein encapsulation technologies of polymeric microspheres currently in use have been optimized to effectively protect their “protein cargo” from inactivation occurring in biological environments, preserving its bioactivity during release up to several weeks. The scenario of protein delivery would greatly benefit by strategies enabling the production of non-spherical particles. Herein we report an easy and effective stamp-based method to produce poly-lactic-glycolic-acid (PLGA) microparticles encapsulating Vascular Endothelial Growth Factor (VEGF) of different shapes. We demonstrate that PLGA microspheres can be deformed at room temperature exploiting solvent/non-solvent plasticization in order to preserve the properties of the starting microspheres. This gentle method allows the production of shaped particles that provide a prolonged release of VEGF in active form, as verified by an angiogenic assay. The retention of the biological activity of an extremely labile molecule, i.e. VEGF, lets us hypothesize that a wide variety of drug and protein encapsulated polymeric microspheres can be processed using this method.

The role of capsule stiffness on cellular processing

Particle stiffness is emerging as an important parameter in determining the cell uptake dynamics of particles. Understanding the effects of capsule stiffness on their biological behavior is essential for the development of polymer capsules as therapeutic carriers. Herein, we report the preparation of polysaccharide capsules via atom transfer radical polymerization-mediated continuous assembly of polymers (CAPATRP) on silica templates using methacrylated hyaluronic acid (HA) as the macrocrosslinker. This approach affords HA capsules with controllable wall thickness and tunable stiffness. The influence of capsule stiffness on cellular interaction and intracellular distribution is systematically investigated using flow cytometry, imaging flow cytometry, and deconvolution microscopy. The softest HA capsules with a stiffness (γ) of 7.5 mN m-1 possess higher cell surface binding and cellular association when compared to stiffer capsules with γ of 17.6-28.9 mN m-1. Furthermore, the uptake of HA capsules is a stiffness-dependent process, with slower and less cellular internalization observed with increasing capsule stiffness. Nevertheless, regardless of the stiffness, all internalized capsules are deformed and located in the lysosomes. These findings offer insights into the influence of capsule stiffness on cellular interaction as well as intracellular fate, providing information for the design of rational polymer capsules for biomedical applications.