Patient-specific, mechanistic models of tumor growth incorporating artificial intelligence and big data

Despite the remarkable advances in cancer diagnosis, treatment, and management that have occurred over the past decade, malignant tumors remain a major public health problem. Further progress in combating cancer may be enabled by personalizing the delivery of therapies according to the predicted response for each individual patient. The design of personalized therapies requires patient-specific information integrated into an appropriate mathematical model of tumor response. A fundamental barrier to realizing this paradigm is the current lack of a rigorous, yet practical, mathematical theory of tumor initiation, development, invasion, and response to therapy. In this review, we begin by providing an overview of different approaches to modeling tumor growth and treatment, including mechanistic as well as data-driven models based on ``big data" and artificial intelligence. Next, we present illustrative examples of mathematical models manifesting their utility and discussing the limitations of stand-alone mechanistic and data-driven models. We further discuss the potential of mechanistic models for not only predicting, but also optimizing response to therapy on a patient-specific basis. We then discuss current efforts and future possibilities to integrate mechanistic and data-driven models. We conclude by proposing five fundamental challenges that must be addressed to fully realize personalized care for cancer patients driven by computational models

The role of ultrasound-driven microbubble dynamics in drug delivery : from microbubble fundamentals to clinical translation

In the last couple of decades, ultrasound-driven microbubbles have proven excellent candidates for local drug delivery applications. Besides being useful drug carriers, microbubbles have demonstrated the ability to enhance cell and tissue permeability and, as a consequence, drug uptake herein. Notwithstanding the large amount of evidence for their therapeutic efficacy, open issues remain. Because of the vast number of ultrasound- and microbubble-related parameters that can be altered and the variability in different models, the translation from basic research to (pre)clinical studies has been hindered. This review aims at connecting the knowledge gained from fundamental microbubble studies to the therapeutic efficacy seen in in vitro and in vivo studies, with an emphasis on a better understanding of the response of a microbubble upon exposure to ultrasound and its interaction with cells and tissues. More specifically, we address the acoustic settings and microbubble-related parameters (i.e., bubble size and physicochemistry of the bubble shell) that play a key role in microbubble cell interactions and in the associated therapeutic outcome. Additionally, new techniques that may provide additional control over the treatment, such as monodisperse microbubble formulations, tunable ultrasound scanners, and cavitation detection techniques, are discussed. An in-depth understanding of the aspects presented in this work could eventually lead the way to more efficient and tailored microbubble-assisted ultrasound therapy in the future

Immuno Magnetic Thermosensitive Liposomes For Cancer Therapy

The present work describes the encapsulation of the drug doxorubicin (DOX) in immuno paramagnetic thermosensitive liposomes. DOX is the most common chemotherapeutic agent for the treatment of a variety of carcinomas. However, the pure drug has high cytotoxicity and therefore requires a targeted and biocompatible delivery system. The introduction includes concepts, modalities, and functionalities of the project. First, a detailed description of the cell type (triple-negative breast cancer) is given. Furthermore, the importance of liposomal doxorubicin is explained and the current state of research is shown. The importance of modification to achieve thermosensitive properties and the procedure for co-encapsulation with Gd chelate to achieve paramagnetic properties is also discussed. In addition, the first part describes the surface modification with ADAM8 antibodies, which leads to improved targeting. The second part of the thesis covers the different materials and methods used in this paper. The production of the liposomes LipTS, LipTS-GD, LipTS-GD-CY, LipTS-GD-CY-MAB and the loading of DOX using an ammonium sulfate gradient method were described in detail. The results part deals with the physicochemical characterization using dynamic light scattering and laser Doppler velocimetry, which confirmed a uniform monodisperse distribution of the liposomes. These properties facilitate the approach of liposomes to target cancer cells. The influence of lipid composition of liposomes, co-encapsulation with Gd chelate and surface modification of liposomes was evaluated and described accordingly. The size and structure of the individual liposomal formulations were determined by atomic force microscopy and transmission electron microscopy. Morphological examination of the liposomes confirmed agreement with the sizes obtained by dynamic light scattering. Temperature-dependent AFM images showed an intact liposome structure at 37 °C, whereas heating by UHF-MRI led to a lipid film indicating the destruction of the lipid bilayer. Furthermore, TEM images showed the morphological properties of the liposomes and gave a more precise indication of how Gd-chelate accumulates within the liposomes. Liposomes with Gd-chelate showed well-separated vesicles, suggesting that Gd- chelate is deposited in the lipid bilayer of the liposomes. Gd was encapsulated in the hydrophilic core whereas chelate was extended into the lipid bilayer. By differential scanning calorimetry and drug release, the heat-sensitive functionality of the liposomes could be determined. Liposomes showed a beginning of phase transition temperature at about 38 °C, which can be achieved by UHF-MRI exposure. The maximum phase transition temperature in the case of LipTS-GD and LipTS-GD-CY-MAB was 42 °C and 40 °C, respectively. A proof of concept study for the thermosensitive properties of liposomes and a time-dependent DOX release profile in hyperthermia was performed. Gd-chelate is encapsulated in both LipTS-GD and LipTS-GD-CY-MAB and led to paramagnetic properties of the liposomes. This facilitates imaging mediated DOX delivery and diagnosis of the solid tumor and metastatic cells. The change in relaxation rate R1 of liposomes was quantified before and after heating above Tm (T> Tm). The relaxivity of the liposomes was obtained from the adapted slope of the relaxation rate against the Gd concentration. Remarkably, the relaxation rate and relaxivity increased after heating the liposomes above Tm (T> Tm), suggesting that the liposomes opened, released Gd chelate, and the exchange of water molecules became faster and more practicable. Toxicity studies describe the different mechanisms for induced DOX toxicity. The increased cytotoxic effect at elevated temperatures showed that the induced toxicity is thermally dependent, i.e. DOX was released from the liposomes. The high viability of the cells at 37 °C indicates that the liposomes were intact at normal physiological temperatures. Under UHF-MRI treatment, cell toxicity due to elevated temperature was observed. The cellular uptake of liposomes under UHF-MRI was followed by a confocal laser scanning microscope. An increase in fluorescence intensity was observed after UHF-MRI exposure. The study of the uptake pathway showed that the majority of liposomes were mainly uptake by clathrin-mediated endocytosis. In addition, the liposomes were modified with anti-ADAM8 antibodies (MAB 1031) to allow targeted delivery. The cellular binding capabilities of surface-modified and non-modified liposomes were tested on cells that had ADAM8 overexpression and on ADAM8 knockdown cells. Surface-modified liposomes showed a significant increase in binding ability, indicating significant targeting against cells that overexpress ADAM8 on their surface. In addition, cells with knockdown ADAM8 could not bind a significant amount of modified liposomes. The biocompatibility of liposomes was assessed using a hemolysis test, which showed neglected hemolytic potential and an activated thromboplastin time (aPTT), where liposomes showed minimal interference with blood clotting. Hemocompatibility studies may help to understand the correlation between in vitro and in vivo. The chorioallantois model was used in ovo to evaluate systematic biocompatibility in an alternative animal model. In the toxicity test, liposomes were injected intravenously into the chicken embryo. The liposomes showed a neglectable harmful effect on embryo survival. While free DOX has a detrimental effect on the survival of chicken embryos, this confirms the safety profile of liposomes compared to free DOX. LipTS-GD-CY-MAB were injected into the vascular system of the chicken embryo on egg development day 11 and scanned under UHF-MRI to evaluate the magnetic properties of the liposomes in a biological system with T2-weighted images (3D). The liposomal formulation had distinct magnetic properties under UHF MRI and the chick survived the scan. In summary, immunomagnetic heat-sensitive liposomes are a novel drug for the treatment of TNBC. It is used both for the diagnosis and therapy of solid and metastasizing tumors without side effects on the neighboring tissue. Furthermore, a tumor in the CAM model will be established. Thereafter, the selective targeting of the liposomes will be visualized and quantitated using fluorescence and UHF-MRI. Liposomes are yet to be tested on mice as a xenograft triple-negative breast cancer model, in which further investigation on the effect of DOX-LipTS-GD-CY-MAB is evaluated. On one hand, the liposomes will be evaluated regarding their targetability and their selective binding. On the other hand, the triggered release of DOX from the liposomes after UHF-MRI exposure will be quantitated, as well as evaluate the DOX-Liposomes therapeutic effect on the tumor

Advances in MRI-Based Detection of Cerebrovascular Changes after Experimental Traumatic Brain Injury

Traumatic brain injury is a heterogeneous and multifaceted neurological disorder that involves diverse pathophysiological pathways and mechanisms. Thorough characterization and monitoring of the brain’s status after neurotrauma is therefore highly complicated. Magnetic resonance imaging (MRI) provides a versatile tool for in vivo spatiotemporal assessment of various aspects of central nervous system injury, such as edema formation, perfusion disturbances and structural tissue damage. Moreover, recent advances in MRI methods that make use of contrast agents have opened up additional opportunities for measurement of events at the level of the cerebrovasculature, such as blood–brain barrier permeability, leukocyte infiltration, cell adhesion molecule upregulation and vascular remodeling. It is becoming increasingly clear that these cerebrovascular alterations play a significant role in the progression of post-traumatic brain injury as well as in the process of post-traumatic brain repair. Application of advanced multiparametric MRI strategies in experimental, preclinical studies may significantly aid in the elucidation of pathomechanisms, monitoring of treatment effects, and identification of predictive markers after traumatic brain injury

Development of Shear-Thinning and Self-Healing Hydrogels Through Guest-Host Interactions for Biomedical Applications

Hydrogels have emerged as an invaluable class of materials for biomedical applications, owing in part to their utility as structural, bioinstructive, and cell-laden implants that mimic many aspects of native tissues. Despite their many positive attributes, conventional hydrogels face numerous challenges toward translational therapies, including difficulty in delivery (i.e., invasive implantation) as well as limited control over biophysical properties (i.e., porosity, degradation, and strength). To address these challenges, the overall goal of this dissertation was the development of a class of supramolecular hydrogels that can be implanted in vivo by simple injection and that have tunable properties — either innate to the system or achieved through additional modifications. Toward this, we developed guest-host (GH) hydrogels that undergo supramolecular assembly through complexation of hyaluronic acid (HA) separately modified by adamantane (Ad-HA, guest) and β-cyclodextrin (CD-HA, host). Modular modifications were made to GH hydrogels to enable tuning of biophysical properties, including the incorporation of matrix-metalloproteinase cleavable peptides between HA and Ad to form enzymatically degradable assemblies. Additionally, dual-crosslinking (DC) of methacrylated CD-HA (CD-MeHA) and thiolated Ad-HA (Ad-HA-SH) by Michael addition subsequent to GH assembly was explored to stiffen hydrogels in vivo following injection. Finally, injectable and tough double network (DN) hydrogels were fabricated, where GH hydrogels were formed in the presence of an interpenetrating covalent network (methacrylated HA, MeHA) crosslinked by Michael addition with a dithiol under cytocompatible conditions. Both GH and DC hydrogels were further explored in vivo, with application to attenuate the maladaptive left ventricular (LV) remodeling that occurs following myocardial infarction (MI) that can result in heart failure. DC hydrogels reduced stress within the infarct region, prevented early ventricular expansion and thereby ameliorated progressive LV remodeling. Moreover, the preservation of myocardial geometry reduced incidence and severity of ischemic mitral regurgitation — an undesirable and devastating consequence of LV remodeling. Overall, the body of work represents a novel approach to engineer biomaterials with unique properties toward biomedical therapies

Role of food material properties on the mechanisms of solid food disintegration during gastric digestion : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

The stomach is, after the mouth, the major organ for the breakdown of foods by a complex interaction of biochemical and mechanical mechanisms driven by the diffusion of gastric juice and the peristaltic activity of the stomach. The degree of fragmentation of solid food in the stomach and consequent release of nutrients is largely dependent on the food material properties. Despite extensive research directed at the gastric digestion, the establishment of the proper relationship between the initial material properties of foods and their subsequent breakdown during gastric digestion is still far from being fully understood. To bridge the aforementioned knowledge gap, the aim of this thesis was to characterise the relationship between material properties of solid foods (composition and structure) and their disintegration behaviour in the stomach. Sweet potato (steamed and fried) and egg white gels (pH 5 and pH 9 EWGs) were used as starch and protein based-product models, respectively, to develop experimental models to characterise not only the diffusion of gastric juice into the food matrix, but also the mechanisms underlying the biochemical and mechanical degradation of the food matrix during in vitro gastric digestion. Overall results revealed that the porous network created during frying facilitated a faster gastric acid penetration into the sweet potato food matrix than occurred in the less porous steamed sweet potato. Consequently, the fried sweet potato matrix underwent a faster collapsing and quicker softening time during in vitro gastric digestion than the more compact and denser structure of steamed sweet potato. This led to the faster disintegration and subsequent release of β-carotene in the human gastric simulator from the fried sweet potato matrix. A similar effect was demonstrated with the EWG, where the loose protein network of pH 5 EWG exhibited a significantly higher rate of pepsin diffusion, softening, nutrient release and mechanical breakdown compared to the more tightened gel microstructure found in the pH 9 EWG. In conclusion, gastric disintegration and nutrient release within the solid food structures are mainly controlled by the initial food microstructure and composition. Such knowledge will help to identify key factors for the designing of health-promoting food formulations

Surveilling the Distinctive Vascular and Metabolic Features of Tumor Progression and Response to Therapy

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Despite maximal treatment with surgical resection, radiotherapy and temozolomide chemotherapy, prognosis is dismal with median survival around 15 months. GBMs are highly infiltrative tumors that invade into surrounding brain tissue, which makes defining the extent of tumor spread difficult and recurrence common. Radiological identification of GBMs with magnetic resonance imaging (MRI), using transvers (T2) or longitudinal (T1) relaxation contrasts, is a mainstay in the initial diagnosis as well as tracking therapeutic response in GBM. However, there is extreme variability in the structural appearance, size, metabolism, and genetic landscape of GBMs, making imaging characteristics highly heterogeneous and hard to define with tumor progression. Although T2-weighted and contrast-enhanced T1-weighted MRI provides anatomical details of the tumor architecture, these methods can be confounded by pseudoprogression and pseudoresponse in the context of therapy.The GBM microenvironment is characterized by immature vasculature and extracellular acidification due to a metabolic shift towards aerobic glycolysis (Warburg effect). The reduced extracellular pH (pHe) has been associated with promoting angiogenesis and invasion as well as creating an immunosuppressive environment. Given the important contribution of vascular changes and extracellular acidosis to shaping the tumor microenvironment, advanced MRI techniques are needed to better characterize the tumor microenvironment to provide more specific readouts of tumor progression and therapeutic response. Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) is a magnetic resonance spectroscopic imaging (MRSI) technique that utilizes the temperature and pH-dependent hyperfine shifts of paramagnetic agents (e.g., TmDOTP5-) for high resolution, three-dimensional, quantitative temperature and pHe mapping. BIRDS has been used to demonstrate the acidic pH in preclinical models of GBM, where the intratumoral space is highly acidified (pH\u3c6.8) in comparison to healthy brain tissue (pH~7.2) and acidic pH spread beyond the anatomically defined tumor core relates to the invasiveness of the tumors. However, a limitation of the BIRDS technique is the necessity of detectable (\u3e1 mM) levels of contrast agent, which are cleared rapidly by the kidney. To obviate need for surgical intervention (e.g., renal ligation) to stop rapid agent clearance, here we demonstrate that pharmacological inhibition of renal clearance of these agents using probenecid to allow for longitudinal imaging of pHe throughout tumor progression and show that acidosis develops early in tumor progression in human-derived GBM tumors (U87 and U251). Since other tomographic pHe mapping methods are non-quantitative and directly altering pHe in a specific tissue is difficult to implement, we looked to assess the BIRDS-based temperature measurements for verification of the quantitative BIRDS readout. A localized cooling system was used to induce hypothermia in sheep brain to levels suggested to be neuroprotective in hypoxic states. Quantitative temperature mapping using BIRDS showed significantly decreased cerebral temperatures with cooling over all defined brain regions and was in agreement with thermocouple measurements. While pHe is a useful metric, tumor vascularity also shapes tumor metabolism and the microenvironment. BIRDS can be combined with other imaging modalities such as dynamic contrast enhanced (DCE) MRI, which allows quantification of vascular parameters (e.g., permeability) through modeling the dynamic uptake of Gd3+-based contrast agents. Multiparametric characterization of the spatiotemporal changes in cellularity, vascularity and acidosis of U87 and U251 tumors throughout progression showed unique patterns that could be used to identify tumor features and differentiate between tumor types. Finally, pHe readouts have potential as a biomarker of therapeutic response. After finding an increase in pHe after treatment with temozolomide in U251 tumors, we used BIRDS longitudinally to demonstrate normalization of pHe in U87 tumors treated with sorafenib, a nonselective tyrosine kinase inhibitor. Both treatments slowed tumor progression and led to increases of pHe which establishes a role for pHe imaging as an early and sensitive marker of evaluating therapeutic response prior to observable changes in the tumor appearance on standard MRI. The potential of BIRDS is vast and not limited to GBM, or cancer in general. Additional work has demonstrated that an acidic pHe is not limited to preclinical tumor models, but is also found in patient-derived xenograft (PDX) models of metastatic melanoma in the brain. BIRDS can also be utilized in evaluating tumors in any organ, as BIRDS has also shown acidic pHe in models of liver cancer. In summary, this work further expands BIRDS into a broadly applicable longitudinal platform for characterization of the tumor microenvironment and may aid in evaluation of many targeted therapeutic strategies