Chapter 1: Cardiovascular Nanomedicine: From Targeted Delivery to Theranostics

Cardiovascular diseases (CVDs) are ranked as the leading cause of mortality worldwide, imposing a large economic burden on society for healthcare. Epidemiological studies reported a variety of risk-enhancing factors for CVDs, including high blood pressure and cholesterol, overweight, smoking, lack of physical exercise and type 2 diabetes. ¹  Various medical and pharmaceutical strategies have been studied for the treatment of CVDs, and efforts are ongoing to discover new techniques. In recent decades, nanomedicine has shown promising potential for multi-target cardiovascular applications by exploiting the special properties of nanomaterials in extra- and intra-vascular mobility to deliver drugs and/or diagnostic imaging agents. This emerging approach has been used for managing various cardiovascular disorders and risk factors, including myocardial infarction (MI), atherosclerosis (AS), hypertension (HP) and pulmonary arterial hypertension (PAH). ²  For this purpose, various nanodelivery systems have been designed and developed. Nanovesicles (liposomes, niosomes, etc.), polymeric nanoparticles (NPs) [poly(lactic-co-glycolic acid) (PLGA) copolymers, poly(ε-caprolactone), etc.], lipid-based NPs [nanostructured lipid carriers (NLCs), solid lipid NPs (SLNs), etc.] and micelles are some of these nanosystems. ^3–6  Therapeutic nanodelivery systems can localize in pathological sites through the enhanced permeability and retention effect. They can also be actively transferred to a target area by using ligands with high specific affinity to particular receptors. These nanosystems can reduce side effects, increase the accuracy and efficiency of treatment and/or improve diagnosis by targeting high-risk areas with cardiovascular disorders. Furthermore, their biomimetic characteristics, stimuli responsiveness and theranostic aspects could promote the treatment of CVDs. ⁷  This chapter reviews recent advances in nanomedicine applications for the treatment and diagnosis of cardiovascular disorders by addressing some of the most common diseases and risk factors.

MI refers to the irreversible damage to the myocardium caused by the reduction in blood flow in coronary arteries or their blockage. MI can be followed by heart failure and death. ⁸  The most common clinical strategies for treating MI include percutaneous coronary intervention, thrombolysis and coronary artery bypass grafting. Despite the advantage of these methods in decreasing the mortality rate, some of their unpredictable complications, such as ischemia–reperfusion injury, hemorrhage and coronary restenosis, necessitate developing more effective approaches for hypoxic-ischemic tissue rescue, blood flow restoration, cardiac myocyte regeneration and tissue repair with minimum cardiac damage. ⁹  Nanomedicine has opened a new horizon in this field, as NPs have demonstrated good potential in the targeted delivery of therapeutic agents with their controlled release and/or direct impacts on the cardiac cells and prevention of post-MI remodeling. A combination of pro-angiogenesis, anti-apoptosis and anti-inflammatory approaches has been proposed as an effective treatment strategy for MI. ¹⁰  Tanshinone IIA is a phytochemical containing an estrogen ring with inhibitory effects on inflammation and cardiac hypertrophy. Its incorporation into monomethoxy-poly(ethylene glycol)-poly (lactic acid)-d-α-tocopherylpolyethylene glycol 1000 succinate NPs and intravenous injection into mice with left coronary artery ligation prevented the phosphorylation of IκB (inhibitor of NF-κB) and activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells). Treatment with these NPs suppressed the pro-inflammatory cytokine expression, reduced cardiomyocyte apoptosis and fibrotic process, inhibited left ventricle dilation and limited the infarct expansion. ¹¹  Angiogenesis plays a vital role in MI treatment and can alleviate patient symptoms. Vascular endothelial growth factor (VEGF), basic fibroblast growth factor, interleukin-8 (IL-8) and other angiogenic agents can stimulate vessel formation. The short half-life of the growth factors, however, is considered to be a drawback to their effectiveness. In one study, VEGF electrostatically complexed with polyglutamic acid polypeptides was loaded into a hyaluronic acid hydrogel, and the formulation was proposed as a delivery platform for growth factors to ischemic myocardium, providing sustained release of these angiogenic cargoes. ¹²  The application of the bioactive peptide nanofibers has been reported as an efficient approach for post-MI healing. The injection of glycosaminoglycan-mimetic peptide scaffolds in a cardiac infarct rat model increased VEGF-A expression, vascular cell recruitment and angiogenesis in the cardiovascular tissue after MI, providing more cardiac muscle preservation and better cardiac function. ¹³  Blood flow restriction and oxygen deficiency in MI can lead to cardiac cell death. Hence, oxygen delivery to the infarcted site using nanosystems is another effective strategy for restoring cardiac function and cell rescue. Intravenous injection of oxygen-releasing NPs and their accumulation in the infarcted area led to suppressed fibrosis and enhanced neovascularization and cell survival. ¹⁴  Apoptosis has been reported to have a pivotal role in cardiomyocyte death, determining the infarct size in MI and heart failure. In vivo studies have revealed the beneficial effects of apoptosis inhibition on cardiac functions and infarct size reduction in MI models. It has been proposed that tissue necrosis in the infarcted site at the early stage of MI can be decreased by blocking myocardial apoptosis. Nanoprotein complexes can prevent remodeling of the left ventricle in MI patients. These complexes could decrease the myocardial apoptosis-related protein expression in MI rat models and prevent MI cell apoptosis. ¹⁵  MI also involves the infiltration of inflammatory leukocytes into the myocardial area, cytokine production and the triggering of inflammatory responses. Therefore, another suggested strategy to decrease the post-MI myocardial injury is anti-inflammatory therapy. Elevated levels of IL-6, IL-1 and tumor necrosis factor-alpha (TNF-α) have been reported as the contributing factors for myocardial injury and myocyte death. ^16,17  Calcium carbonate NP-based delivery systems containing colchicine reduced the pro-inflammatory cytokine expression in myocardial tissues, the levels of IL-1β and TNF-α in serum, myocardial fibrosis and infarct size after MI. ¹⁸  MiR-199a-3p showed a regulatory effect on cardiomyocyte biology and could promote cardiac function and decrease the infarct size in MI mice models. ¹⁹  NPs coated with macrophage membrane and containing miR-199a-3p could bind to pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β), improve cell proliferation, inhibit hypoxia-induced apoptosis and cardiac fibrosis and suppress inflammation in the MI mice model. ²⁰ 

AS is an inflammatory disease characterized by atherosclerotic plaque formation in specific sites of arteries due to the accumulation of lipids, cholesterol and fibrous elements. Plaque rupture can result in thrombosis and may be followed by life-threatening consequences, such as MI and stroke. ²¹  The main challenges for the management of AS are the development of an efficient targeting nanosystem and the improvement of plaque stability. Oxidative stress and inflammation are among the main triggers for enhancing AS. Targeted delivery of IL-10-encapsulated cyclic arginylglycylaspartic acid (cRGD)-conjugated pluronic-based nanocarriers to atherosclerotic plaques resulted in the decreased generation of IL-1β in AS lesions and a reduction in the plaque size. ²²  Targeted delivery of the designed tetrapod PdH nanozymes to arterial plaques led to the scavenging of reactive oxygen species (ROS), activation of autophagy, reduction of oxidative stress, suppression of inflammation and alleviation of AS progression. ²³  Platelet endothelial cell adhesion molecule-1 (PECAM-1) is one of the adhesion molecules highly expressed during the AS process due to the endothelial inflammatory condition. Anti-PECAM-1 surface-functionalized nanocapsules with the core of the docosahexaenoic acid showed good potential for AS regression. ²⁴  Biomimetic rapamycin-loaded PLGA NPs coated with macrophage membrane were developed for the effective and targeted treatment of AS (Figure 1.1). Integrin α4β1, a protein on the macrophage surface, could bind with the VCAM-1, an antibody on the human umbilical vein endothelial cells, and ensure the active targeting of the dysfunctional endothelium. In vitro studies revealed the sustained release kinetics of rapamycin and internalization of the NPs by umbilical vein endothelial and RAW264.7 cells. The results showed the accumulation of these nanosystems in atherosclerotic lesions and their inhibitory effects on the progression of AS in the mouse model. ²⁵ 

The promotion of plaque stability is a critical consideration in AS management. Angiogenesis in atherosclerotic lesions leads to plaque growth and instability. ²⁶  Ginsenoside and catalase-co-loaded porous PLGA NPs with surface modification with U937 cell membranes targeted atherosclerotic plaques and reduced the progression of AS through a process involving anti-angiogenesis; scavenging of ROS; downregulation of IL-1β, TNF-α and intercellular adhesion molecule-1 (ICAM-1) and anti-oxidant and anti-inflammatory activities. ²⁷  A biomimetic nanodelivery system developed by platelet membrane cloaking around selenium and ginsenoside Rb1 NPs led to anti-inflammatory, anti-oxidant and anti-angiogenic effects. ²⁸  As the AS progression is essentially affected by cholesterol crystals in plaques, designing and developing nanosystems for cholesterol crystal removal can be a promising approach to inhibit AS-related cardiovascular diseases. Several studies have indicated the role of liposomes as cholesterol-lowering agents in the treatment of AS. ^29,30  Nano-sponge-like liposomes containing ginsenosides Rb1 and surface-decorated with Annexin V showed anti-AS activity. They accumulated in atherosclerotic plaques, eliminated intra- and extra-cellular cholesterol, promoted cholesterol efflux and reduced apoptosis and inflammation in plaques. The plaque targeting was mediated by the ability of Annexin V to recognize phosphatidylserine (PS), which is upregulated in the plaques. The incorporation of ginsenosides Rb1 into the lipid bilayer increased the bilayer affinity to the cholesterol and cholesterol crystal solubilization. ³¹  Targeted delivery of coding or non-coding nucleic acid-loaded NPs is another nanomedicinal strategy to treat AS. Several studies have reported promising results on vascular wall targeting by microRNAs, such as miR-33, miR-21, miR-143 and miR-145. ³²  Noncationic nanostructures with a core of polyethylene glycol-coated superparamagnetic iron oxide NPs and a shell of phosphorothioate-modified miR-146a oligonucleotides were developed. Repeated intravenous injection of these nanostructures into the ApoE^−/− mice alleviated AS by reducing and stabilizing the atherosclerotic plaques. This therapeutic approach was attributed to the effect of miR-146a-superparamagnetic iron oxide NPs in downregulating the expression of the genes related to vascular inflammation and immune responses. These NPs targeted the scavenger receptors of the endothelial cells and macrophages and enhanced the delivery of these nanostructures to the plaques. ³³ 

Nanomedicine has demonstrated great potential in normalizing abnormal heart rhythms by promoting the benefits of anti-arrhythmic agents, such as beta-blockers and sodium, potassium and calcium channel blockers. ³⁴  Guanfu base A is a sodium and potassium channel antagonist. The solid nanolipids loaded with Guanfu base A caused a longer blood circulation time of the payload and a better anti-arrhythmic effect, especially in ventricular tachycardia and ectopia, than Guanfu base A HCl solution in rodent models. ³⁵  Chitosan NPs containing botulinum toxin showed an antagonistic effect on the arrhythmia caused by the activation of cardiac ion channels. ³⁶  Several nanosystems were developed to alleviate a common type of cardiac arrhythmia, called atrial fibrillation. ³⁷  In this case, the localized release of the anti-arrhythmic and anti-inflammatory agents can act more effectively than intravenous injections. Parylene-C-nanostructured films loaded with amiodarone and dexamethasone efficiently released their payloads, prevented fibrotic tissue adhesion and reduced inflammation and atrial fibrillation. ³⁸ 

Hypertension, the elevation of blood pressure to 140/90 mm Hg, is considered a crucial risk factor for cardiovascular diseases. ³⁹  Heart failure, carotid atherosclerosis, left ventricular hypertrophy and peripheral vascular diseases are among the complications caused by high blood pressure. ⁴⁰  Angiotensin-converting enzyme inhibitors, beta-blockers, angiotensin receptor blockers and calcium channel blockers are the main therapeutic agents for treating hypertension. These agents can be administered in combination according to the guidelines. Combining angiotensin receptor blockers with calcium channel blockers has been effective in reducing blood pressure and controlling other cardiovascular events. ⁴¹  One of the approaches for HP management is the oral administration of angiotensin-converting enzyme inhibitors. The application of nanocarriers has facilitated the controlled delivery and release of these compounds. Some bioactive peptides possess angiotensin-converting enzyme-inhibitory activity, but their poor bioavailability, short half-life and high reactivity with other components of the formulation hinder their oral administration. Loading such peptides into nanosystems has been suggested as a strategy to overcome the obstacles to their oral delivery. ^42,43  Transdermal delivery of ethosomal hydrogels loaded with carvedilol, a beta-blocker, provided a proper anti-hypertensive effect with the controlled release of the payload. The tail-cuff measurement method showed that these nanosystems gradually reduced systolic blood pressure within 24 h in sodium chloride-induced hypertensive rat models. ⁴⁴  Transdermal delivery of nanoethosomal formulations loaded with valsartan, an angiotensin II receptor antagonist, in medroxyprogesterone acetate-induced hypertensive rats effectively controlled the blood pressure for up to 48 h. Controlled release of valsartan from these formulations caused a gradual reduction in blood pressure. ⁴⁵  The major goals of nanomedicine in the regulation of hypertension are increased bioavailability and controlled release of anti-hypertensive agents. For example, nisoldipine, a calcium channel antagonist, has a poor oral bioavailability of 5% due to pre-systemic metabolism and its role as a substrate for cytochrome P4503A4 enzymes. ⁴⁶  Several studies have suggested the use of nano-based methodologies to improve its bioavailability. NLCs and SLNs were developed for the delivery of nisoldipine, and NLCs improved the oral bioavailability of the payload by 1.09- and 2.46-fold compared to SLN and nisoldipine suspension, respectively. ⁴⁷  PLGA NPs loaded with nisoldipine and piperine reduced the systemic blood pressure in rats by more than 28% in comparison to nisoldipine suspension. Piperine acted as a cytochrome P4503A4 enzyme inhibitor and caused a 4.9-fold enhancement in nisoldipine bioavailability. ⁴⁶ 

Restriction of the cross-sectional area for blood flow through pulmonary arterial circulation results in PAH, increasing the workload on the right side of the heart. Conventional therapeutic approaches for PAH have exploited targeting the prostacyclin, nitric oxide (NO) and endothelin pathways. ⁴⁸  Nebulization of sildenafil-laden NLCs and SLNs for PAH treatment in rats protected the normal lung parenchyma and minimized excessive vasodilation and intra-alveolar bleeding. Utilization of NLCs led to low interaction with mucin, efficient nebulization and a higher cell viability than SLNs. ⁴⁹  Nanosized metal–organic frameworks have been proposed for the delivery of anti-PAH agents, as they are biocompatible and have a high drug-loading capacity, tunable size, shape and chemical nature and controllable drug-binding and release kinetics. NanoMIL-89, a nano-sized, iron-based metal–organic framework, loaded with sildenafil, exhibited sustained vasodilation in the mouse aorta, with an initial lag phase, which was in line with the payload release. ⁵⁰  Injection of nanospheres containing ONO1301, a prostacyclin agonist, into the Sugen/hypoxia rat models led to a reduction in IL-1β, IL-6, transforming growth factor-β (TGF-β) and platelet-derived growth factor-β levels. Furthermore, it caused an increase in the expression of hepatocyte growth factor and an improvement in the percent medial wall thickness of the pulmonary vasculature and right ventricle pressure/left ventricle pressure in rats. ⁵¹  The pressure and hypertrophy of the right ventricle and muscularization of the pulmonary artery in PAH rat models were reduced by the intratracheal administration of beraprost NPs. The NPs incorporating this prostacyclin analog exhibited a sustained anti-proliferative effect on the smooth muscle cells of the pulmonary arteries. ⁵²  NO possesses vasodilatory, anti-coagulant and antiproliferative properties, and the NO nanoformulations released NO with a kinetics consisting of an initial peak followed by a sustained release. These nanosystems induced the relaxation of the pulmonary arteries of hypoxia-induced PAH mice in a concentration-dependent manner. ⁵³  Oral delivery of NPs containing bosentan, an endothelin receptor antagonist, prevented oxidative stress and cell proliferation and exhibited protective effects on smooth muscle cells of the pulmonary arteries. ⁵⁴  Nanoencapsulation of bosentan can overcome the usual restricting aspects for its oral delivery, including low active time and bioavailability, the need for frequent administration, side effects and liver toxicity. Intratracheal administration of cerivastatin nanoliposomes prevented the smooth muscle cell proliferation in pulmonary arteries, exhibited sustained release kinetics and provided safe drug delivery for PAH treatment, without cytotoxicity and with less lactone metabolite formation compared to free cerivastatin. ⁵⁵ 

The use of stimuli-responsive nanomedicines has opened a new horizon in overcoming the limitations of conventional approaches in CVD treatment. Such nanomedicines can adjust the release of a therapeutic agent in response to endogenous stimuli, including changes in pH and ROS levels at the pathological site, and/or exogenous stimuli, including magnetic fields, ultrasound and light. To treat inflammation and oxidative stress associated with AS, ROS-responsive nanomicelles composed of poly(ethylene glycol)-poly(propylene sulfide) and containing the botanical anti-inflammatory agent, andrographolide, were designed and developed. These polymeric nanomicelles reduced the ROS level and the expression of monocyte chemoattractant protein-1 and IL-6 (pro-inflammatory cytokines). Plaque-targeted release was achieved through the reaction between poly(propylene sulfide) and ROS, which caused micellar decomposition. ⁵⁶  The stimulus-responsive drug release nanosystems can exploit the ROS-laden and acidic environment of the MI site as a trigger. A multifunctional hydrogel containing recombinant humanized collagen type III and curcumin-loaded PLGA NPs was developed to obtain the properties of direct injectability into the myocardial wall and on-demand release in response to the microenvironment of the MI site. This hydrogel accelerated angiogenesis, decreased apoptosis, prevented inflammatory responses, healed the damaged heart and promoted cardiac function. ⁵⁷  The pH-responsive tannic acid/europium coordination nanocomplex showed a sustained release behavior in the acidic microenvironment, increased anti-oxidation and neovascularization, prevented inflammatory responses and decreased the infarct size. ⁵⁸ 

Nanomaterial-mediated photothermal therapy (PTT) benefits from an increase in temperature (hyperthermia) in the target area by converting light energy into heat. Most of the studies on PTT have been performed using near-infrared (NIR) light. ⁵⁹  NPs containing nanophotosensitizers, with passive or active targeting, can accumulate in thrombi or atherosclerotic plaques, and through hyperthermia, they can cause loosening of the blood clot and plaque reduction by the destruction of the interactions between fibrins and ablation of the macrophages, respectively. ⁶⁰  Immunoliposomes conjugated with single-chain variable fragment antibody (scFv) and loaded with IR780 dye showed efficient PTT for acute thrombosis, and their use was proposed as a superior, alternative approach to the plasminogen activator-based thrombolysis with bleeding complications. Thanks to the presence of the scFv antibody and IR780, these nanoliposomes could target activated platelets and induce hyperthermia with an average local temperature increase of 12 °C under NIR irradiation, leading to the reduction in the clot area in an FeCl₃-induced thrombosis mouse model. Co-loading of these nanosystems with low-dose, single-chain urokinase plasminogen activator (scuPA) caused a synergistic effect of hyperthermia-induced liposome penetration into clots and fibrinolytic effect in vitro. Co-loading of scuPA, however, did not significantly improve thrombolysis in vivo, confirming the potent photothermal effect for sufficient thrombolysis without the need for other fibrinolytic agents. ⁶¹ 

In photodynamic therapy (PDT), photosensitizers accumulate in the target site, act as energy transfer catalysts, absorb light and result in cytotoxic ROS release. ⁶²  Under NIR irradiation, RGD-modified mesoporous carbon nanospheres containing porphyrin-like metal centers caused site-specific thrombolysis via the synergistic effects of hyperthermia and ROS. ⁶³  These nanosystems overcame the hemorrhagic risk of systematic fibrinolytic agents by targeting the glycoprotein IIb/IIIa receptors on the thrombus. The combination of PDT with PTT inhibited the secondary embolism caused by post-photothermal fragments. PDT-induced ROS, generated by NPs, caused lipid peroxidation and damaged platelet factor 3 (Figure 1.2).

ROS generation via the activation of sonosensitive materials under low-frequency ultrasound, as the stimuli, has been used in sonodynamic therapy (SDT), which showed a higher efficacy endowed by the potent penetration of ultrasound. ⁶⁴  SDT utilizing curcumin nanosuspensions resulted in proper anti-AS effect and plaque stability. This technique increased the level of ROS in RAW264.7 cells, promoted macrophage apoptosis, decreased the levels of low-density lipoprotein and total cholesterol and stimulated macrophage transformation from M1 (pro-inflammatory phenotype) to M2 (reparative phenotype). ⁶⁵ 

Extending the patient’s life, preventing the occurrence of fatal conditions and ensuring effective and successful treatment require the early diagnosis of CVD. Nanomedicine has facilitated the early detection of CVDs by using nanomaterials as contrast agents, including gold nanoshells, colloidal nanobeacons, quantum dots and iodine-based and iron oxide NPs. These nanosystems can be used in different diagnostic techniques, such as optical coherent tomography (OCT), photoacoustic imaging (PAI), fluorescence tomography, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). ⁶⁶  The cLABL peptide-functionalized gold nanoshells exhibited binding capability for the ICAM-1 molecule, a molecule overexpressed in the earliest stage of AS, and acted as great contrast agents for OCT. ⁶⁷  PAI, by merging ultrasound detection and optical illumination, serves as a hybrid imaging modality with high sensitivity for exceptional spatial resolution. ⁶⁸  Using a PAI system with a contrast agent of nanometric, near-infrared, erythrocyte-derived transducers provided suitable capability in finding the location of mimicked vulnerable plaques and stenosis/occlusion-induced MI in the left anterior descending coronary artery ligation mice models (Figure 1.3). ⁶⁹ 

A smart activatable MRI nanosensor, composed of iron oxide NP coated with a gadolinium layer, showed promising results in detecting thrombosis and distinguishing fresh and constituted thrombi through switchability between the T1 and T2 signals. Thrombus targeting of the nanosensor was achieved by its functionalization with fibrin-binding peptide. ⁷⁰  An innovative contrast agent for noninvasive magnetic resonance/fluorescence imaging constructed by covalently attaching a 16-mer peptide (LSLERFLRCWSDAPAK), PP1, to gadolinium-functionalized gold nanoclusters demonstrated superb potential for the precise diagnosis of vulnerable atherosclerotic plaques. This dual-modality imaging probe was designed based on targeting the scavenger receptor AI (one of the isoforms of scavenger receptor A) and its high affinity to PP1. Fluorescence characteristics and longitudinal relaxivity were promoted due to the co-existence of gold and gadolinium species. The images obtained from in vivo studies on established ApoE^−/− mice models exhibited prolonged and robust enhancement of the contrast of the vulnerable plaques, validating the targeting efficacy of these nanosystems. ⁷¹  Paramagnetic/fluorescent micellar NPs were developed and used for in vivo cardiac magnetic resonance visualization and for detecting the MI onset by targeting the highly expressed extracellular matrix metalloproteinase inducer. ⁷²  PET/CT imaging with extracellular loop 1 inverso peptide-conjugated gold nanoclusters radiolabeled with ⁶⁴Cu showed promising potential for clinical translation and acted as a molecular imaging probe for precisely detecting the initiation and progression of AS in the ApoE^−/− mice. This technique exploited the chemokine receptor 2 as an AS marker. ⁷³ 

The detection of biomarkers by nanomaterial-based biosensors has been proposed as a rapid and precise diagnosis strategy for early-stage CVDs. Furthermore, signals can be amplified through the benefits of multiple structures of hybrid nanomaterials and/or high loading capacity for recognition elements by exploiting the high surface-area-to-volume ratio and porous structures of nanomaterials. Troponin T, a cardiac biomarker, was detected by a label-free electrochemical biosensor consisting of ZnSnO₃ perovskite nanomaterials with sub-femtomolar detection sensitivity. ⁷⁴  Detection of myoglobin, an MI biomarker, was performed using a label-free, surface-enhanced Raman scattering sensor composed of 3D silver anisotropic nano-pinetree array-modified indium tin oxide substrates, with a detection limit of 10 ng mL⁻¹. ⁷⁵  An electrochemical aptasensor demonstrated a promising potential for the early diagnosis of MI in clinical applications. It was constructed using gold NP-decorated boron nitride nanosheets and developed for selectively detecting myoglobin with high sensitivity and a low detection limit. ⁷⁶  A porous early detector for CVD biomarkers, composed of hydrogen-substituted graphdiyne and nanodiamonds, was developed as an impedimetric aptasensor for detecting myoglobin and cardiac troponin I with low limits of 9.04 and 6.29 fg mL⁻¹, respectively. ⁷⁷  One of the point-of-care diagnosis strategies for CVDs is the use of smartphone-based methodologies and microRNAs as biomarkers. ⁷⁸  A nanosystem composed of a gold NP core and a G-quadruplex DNAzyme layer was used as a catalytic nanolabel for chemiluminescence microRNA imaging by using a smartphone. This technique exhibited great performance in imaging and analyzing miRNA-133a, a biomarker for MI onset, in patients’ serum. ⁷⁹ 

The design and development of nanosystems for simultaneously delivering therapeutic and diagnostic agents and continuously monitoring CVDs have received a great deal of attention in recent decades. Multimodal imaging-guided SDT using ramucirumab-modified PLGA NPs encapsulating hematoporphyrin monomethyl ether, manganese ferrite and perfluoropentane demonstrated an effective approach for theranostics of plaque angiogenesis. These NPs could accumulate in neovessels of the plaque by actively targeting the mitochondria of rabbit aortic endothelial cells, and MRI/PAI/ultrasound (US) imaging provided real-time observation of their distribution in plaques. ⁸⁰  Hematoporphyrin monomethyl ether and perfluoropentane were used for SDT and ultrasound imaging, respectively. The manganese ferrite was encapsulated into NPs for PAI and MRI T1. NP‐mediated SDT generated ROS, prevented migration and proliferation of aortic endothelial cells, induced mitochondrial-caspase apoptosis and inhibited the neovascularization in plaque (Figure 1.4).

Dual-targeted, high-density lipoprotein-mimicking NPs, incorporating the apolipoprotein A1-mimetic L-4F peptide, stearyl triphenylphosphonium, stearyl mannose and mito-magneto, exhibited the potential ability to act as nanotheranostic agents for CVDs. The surface functionalization conferred the NPs with the capability to remove lipids and target the M2 macrophages and mitochondria. In parallel, encapsulating the mito-magneto, a hydrophobic contrast agent for MRI, in the core of these NPs led to MRI contrast enhancement. ⁸¹  Accurate early diagnosis and site-specific treatment of MI were achieved by a theranostic nanosystem composed of PS, poly(lactide)-polycarboxybetaine and magnetic iron oxide nanocubes. The nanosystems were intravenously administered into MI rat models and accumulated at the infarcted site via external magnetic field induction, mimicking apoptosis. The binding of PS to its receptors on the macrophage surface induced the modulation of the macrophage phenotype from M1 to M2, which facilitated the upregulation of the anti-inflammatory regulators IL-10 and TGF-β1, downregulation of the pro-inflammatory cytokine TNF-α, resolution of the initial inflammation, revascularization, improvement of MI healing and promotion of cardiac function. Lysosomal/endosomal escape of magnetic iron oxide nanocubes was mediated by protonated polycarboxybetaine, resulting in promoted cytoplasmic accumulation of nanocubes. A high-sensitivity and precise MRI with reduced signal intensity in T2* was obtained by these nanosystems. ⁸² 

A theranostic nanosystem for thrombosed vessels was synthesized by self-assembling the fluorescent IR820-conjugated H₂O₂‑responsive boronate polymers and lipopeptide for targeting the fibrin. This nanosystem prevented H₂O₂ production, suppressed soluble CD40 ligand and TNF-α expression in activated platelets and exerted anti-inflammatory, anti-oxidant and anti-thrombotic effects. Furthermore, it demonstrated fibrin-targeted imaging capability and fluorescence/photoacoustic signal enhancement in the FeCl₃-induced carotid arterial thrombosis mouse model. ⁸³ 

In recent decades, nanomedicine has attracted increasing attention as an emerging strategy to deal with the challenges of treatment and diagnosis of cardiovascular disorders. Despite the great achievements reviewed in this chapter, cardiovascular nanomedicine has a long way to pave for successful global clinical translation and commercialization. In this regard, quality control, reproducibility, cost-effective scale-up process, safety and toxicity issues, legislation and establishment of standards are among the most important aspects that have to be considered to achieve a precise and efficient approach with improved patient outcomes. More efforts are needed for the rapid development of theranostic nanomedicine as a non-invasive simultaneous diagnostic and therapeutic strategy. Integrating these advances with those in materials engineering, chemistry, biology and physics will lead to a revolution in cardiovascular nanomedicine in the future.