Multifunctional superparamagnetic iron oxide nanoparticles for combined chemotherapy and hyperthermia cancer treatment

Superparamagnetic iron oxide (SPIO) nanoparticles have the potential for use as a multimodal cancer therapy agent due to their ability to carry anticancer drugs and generate localized heat when exposed to an alternating magnetic field, resulting in combined chemotherapy and hyperthermia. To explore this potential, we synthesized SPIOs with a phospholipid-polyethylene glycol (PEG) coating, and loaded Doxorubicin (DOX) with a 30.8% w/w loading capacity when the PEG length is optimized. We found that DOX-loaded SPIOs exhibited a sustained DOX release over 72 hours where the release kinetics could be altered by the PEG length. In contrast, the heating efficiency of the SPIOs showed minimal change with the PEG length. With a core size of 14 nm, the SPIOs could generate sufficient heat to raise the local temperature to 43 °C, sufficient to trigger apoptosis in cancer cells. Further, we found that DOX-loaded SPIOs resulted in cell death comparable to free DOX, and that the combined effect of DOX and SPIO-induced hyperthermia enhanced cancer cell death in vitro. This study demonstrates the potential of using phospholipid-PEG coated SPIOs for chemotherapy–hyperthermia combinatorial cancer treatment with increased efficacy

Bioactive microstructures for enhanced cardiac recovery after myocardial infarction

Myocardial infarction (MI) is the leading cause of heart failure (HF) and despite advances in the management of MI, subsequent pathologic remodeling of ischemic myocardium with fibrotic scar tissue and aneurysmal degeneration leads to HF and death. Early attempts at stem cell delivery and biological therapeutics to promote positive remodeling following MI have been promising but inconsistent and often involve systemic inhibition of signaling factors, which can have unintended side effects. A compelling approach to combat pathological cellular processes that often arise due to myocardial injury includes engineering materials to mimic biological and physical traits of native ECM architecture to provide biophysical cues that may yield more healthy cell phenotypes. This dissertation describes the therapeutic applications of biophysical cues in cardiovascular diseases (CVDs), specifically myocardial infarction and heart failure. First, Chapter 1 provides a comprehensive discussion regarding how nano- and microscale biophysical cues affect the phenotypes and behaviors of key cardiovascular cells– cardiomyocytes, fibroblasts, and endothelial cells– and how these resulting effects may be leveraged for therapeutic success in CVDs. Chapter 2 then details the development of a biodegradable polymeric microstructure technology made of hyaluronic acid. In this study, we investigated how hyaluronic acid microrods affect fibroblast phenotype and if they can improve cardiac outcomes in rodent models of ischemia-reperfusion (I/R) MI injury. We demonstrated that treatment with hyaluronic acid microrods decreases fibrotic phenotype in fibroblasts as well as exhibits enhanced cardiac function and decreased fibrosis after 6 weeks post-MI. Further, treatment with hyaluronic acid microrods outperformed treatment with equivalent mass of soluble hyaluronic acid material control, indicating the importance of the material geometry. Beyond physical regulation of cellular behaviors by topographical cues, the incorporation of biochemical factors may further enhance the efficacy of these therapeutic strategies. As such, Chapter 3 comprises studies that probed the effects of several pro-angiogenic stimuli (i.e., Qk, RoY, and HepIII peptides) on endothelial cells and the feasibility of conjugating them onto hyaluronic acid microrods to create dual-pronged strategy that tackled both rampant fibrosis and lack of vascularization that occur post-MI. Chapter 4 follows a similar approach but investigates the therapeutic effects of a decorin-loaded hyaluronic acid microrod strategy in rodent models of I/R MI injury. Here, we demonstrate distinguishable improvement in cardiac function and ventricular remodeling and decreased fibrosis and cardiomyocyte hypertrophy in animals treated with decorin-loaded hyaluronic acid microrods. Together, this body of work aims to contribute important knowledge to help develop rationally designed, engineered biomaterials that may be used to successfully treat CVDs

Biomaterials to enhance stem cell transplantation

The successful transplantation of stem cells has the potential to transform regenerative medicine approaches and open promising avenues to repair, replace, and regenerate diseased, damaged, or aged tissues. However, pre-/post-transplantation issues of poor cell survival, retention, cell fate regulation, and insufficient integration with host tissues constitute significant challenges. The success of stem cell transplantation depends upon the coordinated sequence of stem cell renewal, specific lineage differentiation, assembly, and maintenance of long-term function. Advances in biomaterials can improve pre-/post-transplantation outcomes by integrating biophysiochemical cues and emulating tissue microenvironments. This review highlights leading biomaterials-based approaches for enhancing stem cell transplantation

Injectable hyaluronic acid based microrods provide local micromechanical and biochemical cues to attenuate cardiac fibrosis after myocardial infarction.

Repairing cardiac tissue after myocardial infarction (MI) is one of the most challenging goals in tissue engineering. Following ischemic injury, significant matrix remodeling and the formation of avascular scar tissue significantly impairs cell engraftment and survival in the damaged myocardium. This limits the efficacy of cell replacement therapies, demanding strategies that reduce pathological scarring to create a suitable microenvironment for healthy tissue regeneration. Here, we demonstrate the successful fabrication of discrete hyaluronic acid (HA)-based microrods to provide local biochemical and biomechanical signals to reprogram cells and attenuate cardiac fibrosis. HA microrods were produced in a range of physiological stiffness and shown to degrade in the presence of hyaluronidase. Additionally, we show that fibroblasts interact with these microrods in vitro, leading to significant changes in proliferation, collagen expression and other markers of a myofibroblast phenotype. When injected into the myocardium of an adult rat MI model, HA microrods prevented left ventricular wall thinning and improved cardiac function at 6 weeks post infarct

Modular Strategy for the Construction of Radiometalated Antibodies for Positron Emission Tomography Based on Inverse Electron Demand Diels–Alder Click Chemistry

A modular system for the construction of radiometalated antibodies was developed based on the bioorthogonal cycloaddition reaction between 3-(4-benzylamino)-1,2,4,5-tetrazine and the strained dienophile norbornene. The well-characterized, HER2-specific antibody trastuzumab and the positron emitting radioisotopes ⁶⁴Cu and ⁸⁹Zr were employed as a model system. The antibody was first covalently coupled to norbornene, and this stock of norbornene-modified antibody was then reacted with tetrazines bearing the chelators 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA) or desferrioxamine (DFO) and subsequently radiometalated with ⁶⁴Cu and ⁸⁹Zr, respectively. The modification strategy is simple and robust, and the resultant radiometalated constructs were obtained in high specific activity (2.7–5.3 mCi/mg). For a given initial stoichiometric ratio of norbornene to antibody, the ⁶⁴Cu-DOTA- and ⁸⁹Zr-DFO-based probes were shown to be nearly identical in terms of stability, the number of chelates per antibody, and immunoreactivity (>93% in all cases). <i>In vivo</i> PET imaging and acute biodistribution experiments revealed significant, specific uptake of the ⁶⁴Cu- and ⁸⁹Zr-trastuzumab bioconjugates in HER2-positive BT-474 xenografts, with little background uptake in HER2-negative MDA-MB-468 xenografts or other tissues. This modular systemone in which the divergent point is a single covalently modified antibody stock that can be reacted selectively with various chelatorswill allow for both greater versatility and more facile cross-comparisons in the development of antibody-based radiopharmaceuticals

Local decorin delivery via hyaluronic acid microrods improves cardiac performance, ventricular remodeling after myocardial infarction

Heart failure (HF) remains a global public health burden and often results following myocardial infarction (MI). Following injury, cardiac fibrosis forms in the myocardium which greatly hinders cellular function, survival, and recruitment, thus severely limits tissue regeneration. Here, we leverage biophysical microstructural cues made of hyaluronic acid (HA) loaded with the anti-fibrotic proteoglycan decorin to more robustly attenuate cardiac fibrosis after acute myocardial injury. Microrods showed decorin incorporation throughout the entirety of the hydrogel structures and exhibited first-order release kinetics in vitro. Intramyocardial injections of saline (n = 5), microrods (n = 7), decorin microrods (n = 10), and free decorin (n = 4) were performed in male rat models of ischemia-reperfusion MI to evaluate therapeutic effects on cardiac remodeling and function. Echocardiographic analysis demonstrated that rats treated with decorin microrods (5.21% ± 4.29%) exhibited significantly increased change in ejection fraction (EF) at 8 weeks post-MI compared to rats treated with saline (-4.18% ± 2.78%, p &lt; 0.001) and free decorin (-3.42% ± 1.86%, p &lt; 0.01). Trends in reduced end diastolic volume were also identified in decorin microrod-treated groups compared to those treated with saline, microrods, and free decorin, indicating favorable ventricular remodeling. Quantitative analysis of histology and immunofluorescence staining showed that treatment with decorin microrods reduced cardiac fibrosis (p &lt; 0.05) and cardiomyocyte hypertrophy (p &lt; 0.05) at 8 weeks post-MI compared to saline control. Together, this work aims to contribute important knowledge to guide rationally designed biomaterial development that may be used to successfully treat cardiovascular diseases