Edward A. Sykes

Investigating the Impact of Nanoparticle Size on Active and Passive Tumor Targeting Efficiency

Understanding the principles governing the design of nanoparticles for tumor targeting is essential for the effective diagnosis and treatment of solid tumors. There is currently a poor understanding of how to rationally engineer nanoparticles for tumor targeting. Here, we engineered different-sized spherical gold nanoparticles to discern the effect of particle diameter on passive (poly(ethylene glycol)-coated) and active (transferrin-coated) targeting of MDA-MB-435 orthotopic tumor xenografts. Tumor accumulation of actively targeted nanoparticles was found to be 5 times faster and approximately 2-fold higher relative to their passive counterparts within the 60 nm diameter range. For 15, 30, and 100 nm, we observed no significant differences. We hypothesize that such enhancements are the result of an increased capacity to penetrate into tumors and preferentially associate with cancer cells. We also use computational modeling to explore the mechanistic parameters that can impact tumor accumulation efficacy. We demonstrate that tumor accumulation can be mediated by high nanoparticle avidity and are weakly dependent on their plasma clearance rate. Such findings suggest that empirical models can be used to rapidly screen novel nanomaterials for relative differences in tumor targeting without the need for animal work. Although our findings are specific to MDA-MB-435 tumor xenografts, our experimental and computational findings help to enrich knowledge of design considerations that will aid in the optimal engineering of spherical gold nanoparticles for cancer applications in the future.

Tumour-on-a-chip provides an optical window into nanoparticle tissue transport

Nanomaterials are used for numerous biomedical applications, but the selection of optimal properties for maximum delivery remains challenging. Thus, there is a significant interest in elucidating the nano-bio interactions underlying tissue accumulation. To date, researchers have relied on cell culture or animal models to study nano-bio interactions. However, cell cultures lack the complexity of biological tissues and animal models are prohibitively slow and expensive. Here we report a tumour-on-a-chip system where incorporation of tumour-like spheroids into a microfluidic channel permits real-time analysis of nanoparticle accumulation at physiological flow conditions. We show that penetration of nanoparticles into the tissue is limited by their diameter and retention can be improved by receptor-targeting. Nanoparticle transport is predominantly diffusion-limited with convection increasing accumulation exclusively at the tissue perimeter. A murine tumour model confirms these findings and demonstrates that the tumour-on-a-chip can be useful for screening optimal nanoparticle designs prior to in vivo studies.

Dynamic interaction networks in a hierarchically organized tissue

Intercellular (between cell) communication networks maintain homeostasis and coordinate regenerative and developmental cues in multicellular organisms. Despite the importance of intercellular networks in stem cell biology, their rules, structure and molecular components are poorly understood. Herein, we describe the structure and dynamics of intercellular and intracellular networks in a stem cell derived, hierarchically organized tissue using experimental and theoretical analyses of cultured human umbilical cord blood progenitors. By integrating high‐throughput molecular profiling, database and literature mining, mechanistic modeling, and cell culture experiments, we show that secreted factor‐mediated intercellular communication networks regulate blood stem cell fate decisions. In particular, self‐renewal is modulated by a coupled positive–negative intercellular feedback circuit composed of megakaryocyte‐derived stimulatory growth factors (VEGF, PDGF, EGF, and serotonin) versus monocyte‐derived inhibitory factors (CCL3, CCL4, CXCL10, TGFB2, and TNFSF9). We reconstruct a stem cell intracellular network, and identify PI3K, Raf, Akt, and PLC as functionally distinct signal integration nodes, linking extracellular, and intracellular signaling. This represents the first systematic characterization of how stem cell fate decisions are regulated non‐autonomously through lineage‐specific interactions with differentiated progeny.

Cell–cell interaction networks regulate blood stem and progenitor cell fate

Communication networks between cells and tissues are necessary for homeostasis in multicellular organisms. Intercellular (between cell) communication networks are particularly relevant in stem cell biology, as stem cell fate decisions (self‐renewal, proliferation, lineage specification) are tightly regulated based on physiological demand. We have developed a novel mathematical model of blood stem cell development incorporating cell‐level kinetic parameters as functions of secreted molecule‐mediated intercellular networks. By relation to quantitative cellular assays, our model is capable of predictively simulating many disparate features of both normal and malignant hematopoiesis, relating internal parameters and microenvironmental variables to measurable cell fate outcomes. Through integrated in silico and experimental analyses, we show that blood stem and progenitor cell fate is regulated by cell–cell feedback, and can be controlled non‐cell autonomously by dynamically perturbing intercellular signalling. We extend this concept by demonstrating that variability in the secretion rates of the intercellular regulators is sufficient to explain heterogeneity in culture outputs, and that loss of responsiveness to cell–cell feedback signalling is both necessary and sufficient to induce leukemic transformation in silico.

Rapid Screening of Genetic Biomarkers of Infectious Agents Using Quantum Dot Barcodes

The development of a rapid and sensitive infectious disease diagnostic platform would enable one to select proper treatment and to contain the spread of the disease. Here we examined the feasibility of using quantum dot (QD) barcodes to detect genetic biomarkers of the bloodborne pathogens HIV, malaria, hepatitis B and C, and syphilis. The genetic fragments from these pathogens were detected in less than 10 min at a sample volume of 200 μL and with a detection limit in the femtomol range. A next step for the advancement of QD barcode technology to the clinic will require validation of the technology with human samples to assess for matrix effects, head-to-head comparison with existing detection method, development of techniques to automate the assay and detection process, and simplification of analytical device for the read-out of the barcode signal. Our study provides an important intermediate step in the translation of QD barcode technology for screening infectious disease agents in the developed and developing world.

Mechanism of hard-nanomaterial clearance by the liver

The liver and spleen are major biological barriers to translating nanomedicines because they sequester the majority of administered nanomaterials and prevent delivery to diseased tissue. Here we examined the blood clearance mechanism of administered hard nanomaterials in relation to blood flow dynamics, organ microarchitecture, and cellular phenotype. We found that nanomaterial velocity reduces 1000-fold as they enter and traverse the liver, leading to 7.5 times more nanomaterial interaction with hepatic cells relative to peripheral cells. In the liver, Kupffer cells (84.8%±6.4%), hepatic B cells (81.5±9.3%), and liver sinusoidal endothelial cells (64.6±13.7%) interacted with administered PEGylated quantum dots but splenic macrophages took up less (25.4±10.1%) due to differences in phenotype. The uptake patterns were similar for two other nanomaterial types and five different surface chemistries. Potential new strategies to overcome off-target nanomaterial accumulation may involve manipulating intra-organ flow dynamics and modulating cellular phenotype to alter hepatic cell interaction.

Tailoring nanoparticle designs to target cancer based on tumor pathophysiology

Significance Nanotechnology is a promising approach for improving cancer diagnosis and treatment with reduced side effects. A key question that has emerged is: What is the ideal nanoparticle size, shape, or surface chemistry for targeting tumors? Here, we show that tumor pathophysiology and volume can significantly impact nanoparticle targeting. This finding presents a paradigm shift in nanomedicine away from identifying and using a universal nanoparticle design for cancer detection and treatment. Rather, our results suggest that future clinicians will be capable of tailoring nanoparticle designs according to the patients tumor characteristics. This concept of “personalized nanomedicine” was tested for detection of prostate tumors and was successfully demonstrated to improve nanoparticle targeting by over 50%. Nanoparticles can provide significant improvements in the diagnosis and treatment of cancer. How nanoparticle size, shape, and surface chemistry can affect their accumulation, retention, and penetration in tumors remains heavily investigated, because such findings provide guiding principles for engineering optimal nanosystems for tumor targeting. Currently, the experimental focus has been on particle design and not the biological system. Here, we varied tumor volume to determine whether cancer pathophysiology can influence tumor accumulation and penetration of different sized nanoparticles. Monte Carlo simulations were also used to model the process of nanoparticle accumulation. We discovered that changes in pathophysiology associated with tumor volume can selectively change tumor uptake of nanoparticles of varying size. We further determine that nanoparticle retention within tumors depends on the frequency of interaction of particles with the perivascular extracellular matrix for smaller nanoparticles, whereas transport of larger nanomaterials is dominated by Brownian motion. These results reveal that nanoparticles can potentially be personalized according to a patient’s disease state to achieve optimal diagnostic and therapeutic outcomes.

Nanoparticle exposure in animals can be visualized in the skin and analysed via skin biopsy

The increased manufacture and use of nanomaterials raises concerns about the long-term effects of chronic exposure on human health. However, nanoparticle exposure remains difficult to measure. Here we show that mice intravenously administered with high doses of gold nanoparticles have visibly blue skin while quantum dot-treated mice emit green, yellow, or red fluorescence after ultraviolet excitation. More importantly, elemental analysis of excised skin correlates with the injected dose and nanoparticle accumulation in the liver and spleen. We propose that the analysis of skin may be a strategy to quantify systemic nanoparticle exposure and can potentially predict the fate of nanoparticles in vivo. Our results further suggest that dermal accumulation may represent an additional route of nanoparticle toxicity and may be a future strategy to exploit ultra-violet and visible light-triggered therapeutics that are normally not useful in vivo because of the limited light penetration depth of these wavelengths.

A digital microfluidic system for serological immunoassays in remote settings

Portable digital microfluidic serological immunoassays for measles and rubella were developed and evaluated in a remote setting. A fluid transition into the field Many point-of-care diagnostics rely on lateral flow assays or microfluidics; however, these methods generally cannot test multiple samples simultaneously. Ng et al. optimized inkjet-printed digital microfluidic (DMF) cartridges and a portable control system to perform serological immunoassays in remote settings. DMF devices use electrostatic forces to mix and separate reagents and samples in small droplets of fluids. The DMF system measured IgG antibodies for measles and rubella from human blood samples obtained from adults and children on-site in a refugee camp in Kenya. Four samples could be tested simultaneously, although DMF IgG detection was less sensitive and specific than laboratory-based ELISA testing of matched serum samples. The emergence of this field-compatible technology brings with it new tools for advancing global health. Serosurveys are useful for assessing population susceptibility to vaccine-preventable disease outbreaks. Although at-risk populations in remote areas could benefit from this type of information, they face several logistical barriers to implementation, such as lack of access to centralized laboratories, cold storage, and transport of samples. We describe a potential solution: a compact and portable, field-deployable, point-of-care system relying on digital microfluidics that can rapidly test a small volume of capillary blood for disease-specific antibodies. This system uses inexpensive, inkjet-printed digital microfluidic cartridges together with an integrated instrument to perform enzyme-linked immunosorbent assays (ELISAs). We performed a field validation of the system’s analytical performance at Kakuma refugee camp, a remote setting in northwestern Kenya, where we tested children aged 9 to 59 months and caregivers for measles and rubella immunoglobulin G (IgG). The IgG assays were determined to have sensitivities of 86% [95% confidence interval (CI), 79 to 91% (measles)] and 81% [95% CI, 73 to 88% (rubella)] and specificities of 80% [95% CI, 49 to 94% (measles)] and 91% [95% CI, 76 to 97% (rubella)] (measles, n = 140; rubella, n = 135) compared with reference tests (measles IgG and rubella IgG ELISAs from Siemens Enzygnost) conducted in a centralized laboratory. These results demonstrate a potential role for this point-of-care system in global serological surveillance, particularly in remote areas with limited access to centralized laboratories.