Significance: Understanding the interdependency of physiochemical properties of nanomedicine (NM) in correlation to its biological response and function is crucial for additional development of anticancer NM. Here, we prepared monodisperse drug–silica nanoconjugates in three distinct sizes (20, 50, and 200 nm) with other physiochemical properties controlled to be identical to investigate size-dependent biodistribution, tumor tissue penetration and clearance, and anticancer efficacy in various tumor models. We also developed a mathematical model of the spatiotemporal distribution of NM within a tumor to gain insight into the size-dependent interaction with tumor. Our studies show clear evidence that there is an optimal size of anticancer NM and that NM with the optimal size has the highest tumor retention integrated over time.

Hypoxia occurs when limited oxygen supply impairs physiological functions and is a pathological hallmark of many diseases including cancer and ischemia. Thus, detection of hypoxia can guide treatment planning and serve as a predictor of patient prognosis. Unfortunately, current methods suffer from invasiveness, poor resolution and low specificity. To address these limitations, we present Hypoxia Probe 1 (HyP-1), a hypoxia-responsive agent for photoacoustic imaging. This emerging modality converts safe, non-ionizing light to ultrasound waves, enabling acquisition of high-resolution 3D images in deep tissue. HyP-1 features anN-oxide trigger that is reduced in the absence of oxygen by heme proteins such as CYP450 enzymes. Reduction of HyP-1 produces a spectrally distinct product, facilitating identification via photoacoustic imaging. HyP-1 exhibits selectivity for hypoxic activation in vitro, in living cells, and in multiple disease models in vivo. HyP-1 is also compatible with NIR fluorescence imaging, establishing its versatility as a multimodal imaging agent.

Selective targeting of cancer cells is a critical step in cancer diagnosis and therapy. To address this need, DNA aptamers have attracted significant attention as possible targeting ligands. However, while their use in targeting cancer cells in vitro has been reported, their effectiveness has rarely been established in vivo. Here we report the development of a liposomal drug delivery system for targeted anticancer chemotherapy. Liposomes were prepared containing doxorubicin as a payload, and functionalized with AS1411, a DNA aptamer with strong binding affinity for nucleolin. AS1411 aptamer-functionalized liposomes increased cellular internalization and cytotoxicity to MCF-7 breast cancer cells as compared to non-targeting liposomes. Furthermore, targeted liposomal doxorubicin improved antitumor efficacy against xenograft MCF-7 breast tumors in athymic nude mice, attributable to their enhanced tumor tissue penetration. This study suggests that AS1411 aptamer-functionalized liposomes can recognize nucleolin overexpressed on MCF-7 cell surface, and therefore enable drug delivery with high specificity.

Matrix metalloproteinases (MMPs) are postulated to be necessary for neovascularization during wound healing. MMP-9 deletion alters remodeling postmyocardial infarction (post-MI), but whether and to what degree MMP-9 affects neovascularization post-MI is unknown. Neovascularization was evaluated in wild-type (WT; n = 63) and MMP-9 null ( n = 55) mice at 7-days post-MI. Despite similar infarct sizes, MMP-9 deletion improved left ventricular function as evaluated by hemodynamic analysis. Blood vessel quantity and quality were evaluated by three independent studies. First, vessel density was increased in the infarct of MMP-9 null mice compared with WT, as quantified by Griffonia ( Bandeiraea) simplicifolia lectin I (GSL-I) immunohistochemistry. Second, preexisting vessels, stained in vivo with FITC-labeled GSL-I pre-MI, were present in the viable but not MI region. Third, a technetium-99m-labeled peptide (NC100692), which selectively binds to activated α_vβ₃-integrin in angiogenic vessels, was injected into post-MI mice. Relative NC100692 activity in myocardial segments with diminished perfusion (0–40% nonischemic) was higher in MMP-9 null than in WT mice (383 ± 162% vs. 250 ± 118%, respectively; P = 0.002). The unique finding of this study was that MMP-9 deletion stimulated, rather than impaired, neovascularization in remodeling myocardium. Thus targeted strategies to inhibit MMP-9 early post-MI will likely not impair the angiogenic response.

Background— Time-dependent activation of matrix metalloproteinases (MMPs) after myocardial infarction (MI) contributes to adverse left ventricular (LV) remodeling; however, noninvasive methods to monitor this process serially are needed. Methods and Results— MMP-targeted radiotracers were developed that displayed selective binding kinetics to the active MMP catalytic domain. Initial nonimaging studies were performed with a ¹¹¹ In-labeled MMP-targeted radiotracer ( ¹¹¹ In-RP782) and negative control compound ( ¹¹¹ In-RP788) in control mice (Ctrl) and in mice 1 week after surgically induced MI. Localization of ¹¹¹ In-RP782 was demonstrated within the MI by microautoradiography. A 334±44% increase ( P <0.001 versus Ctrl) in relative retention of ¹¹¹ In-RP782 was confirmed by gamma well counting of myocardium. Subsequent high-resolution dual-isotope planar and hybrid micro–single-photon emission computed tomography/CT imaging studies with an analogous ^99m Tc-labeled MMP-targeted radiotracer ( ^99m Tc-RP805) and ²⁰¹ Tl demonstrated favorable biodistribution and clearance kinetics of ^99m Tc-RP805 for in vivo cardiac imaging, with robust retention 1 to 3 weeks after MI in regions of decreased ²⁰¹ Tl perfusion. Gamma well counting yielded a similar ≈300% increase in relative myocardial retention of ^99m Tc-RP805 in MI regions (Ctrl, 102±9%; 1 week, 351±77%; 2 weeks, 291±45%; 3 weeks, 292±41%; P <0.05 versus Ctrl). Myocardial uptake in the MI region was also significantly increased ≈5-fold when expressed as percentage injected dose per gram tissue. There was also a significant 2-fold increase in myocardial activity in remote regions relative to control mice, suggesting activation of MMPs in regions remote from the MI. Conclusions— This novel noninvasive targeted MMP radiotracer imaging approach holds significant diagnostic potential for in vivo localization of MMP activation and tracking of MMP-mediated post-MI remodeling.

Recently, we demonstrated that the heptapeptide angiotensin-(1–7) (Ang-[1–7]) exhibits a favorable kinetic of nitric oxide (NO) release accompanied by extremely low superoxide (O ₂ ⁻ ) production. In this report we describe AVE 0991, a novel nonpeptide compound that evoked effects similar to Ang-(1–7) on the endothelium. AVE 0991 and unlabeled Ang-(1–7) competed for high-affinity binding of [ ¹²⁵ I]-Ang-(1–7) to bovine aortic endothelial cell membranes with IC ₅₀ values of 21±35 and 220±280 nmol/L, respectively. Stimulated NO and O ₂ ⁻ release from bovine aortic endothelial cells was directly and simultaneously measured on the cell surface by selective electrochemical nanosensors. Peak concentrations of NO and O ₂ ⁻ release by AVE 0991 and Ang-(1–7) (both 10 μmol/L) were not significantly different (NO: 295±20 and 270±25 nmol/L; O ₂ ⁻ : 18±2 and 20±4 nmol/L). However, the released amount of bioactive NO was ≈5 times higher for AVE 0991 in comparison to Ang-(1–7). The selective Ang-(1–7) antagonist [D-Ala ⁷ ]-Ang-(1–7) inhibited the AVE 0991–induced NO and O ₂ ⁻ production by ≈50%. A similar inhibition level was observed for the Ang II AT ₁ receptor antagonist EXP 3174. In contrast, the Ang II AT ₂ receptor antagonist PD 123,177 inhibited the AVE 0991–stimulated NO production by ≈90% but without any inhibitory effect on O ₂ ⁻ production. Both NO and O ₂ ⁻ production were inhibited by NO synthase inhibition (≈70%) and by bradykinin B ₂ receptor blockade (≈80%). AVE 0991 efficiently mimics the effects of Ang-(1–7) on the endothelium, most probably through stimulation of a specific, endothelial Ang-(1–7)-sensitive binding site causing kinin-mediated activation of endothelial NO synthase.