The implementation of clinical-decision support algorithms for medical imaging faces challenges with reliability and interpretability. Here, we establish a diagnostic tool based on a deep-learning framework for the screening of patients with common treatable blinding retinal diseases. Our framework utilizes transfer learning, which trains a neural network with a fraction of the data of conventional approaches. Applying this approach to a dataset of optical coherence tomography images, we demonstrate performance comparable to that of human experts in classifying age-related macular degeneration and diabetic macular edema. We also provide a more transparent and interpretable diagnosis by highlighting the regions recognized by the neural network. We further demonstrate the general applicability of our AI system for diagnosis of pediatric pneumonia using chest X-ray images. This tool may ultimately aid in expediting the diagnosis and referral of these treatable conditions, thereby facilitating earlier treatment, resulting in improved clinical outcomes. VIDEO ABSTRACT.

Probing a wide range of cellular phenotypes in neurodevelopmental disorders using patient-derived neural progenitor cells (NPCs) can be facilitated by 3D assays, as 2D systems cannot entirely recapitulate the arrangement of cells in the brain. Here, we developed a previously unidentified 3D migration and differentiation assay in layered hydrogels to examine how these processes are affected in neurodevelopmental disorders, such as Rett syndrome. Our soft 3D system mimics the brain environment and accelerates maturation of neurons from human induced pluripotent stem cell (iPSC)-derived NPCs, yielding electrophysiologically active neurons within just 3 wk. Using this platform, we revealed a genotype-specific effect of methyl-CpG-binding protein-2 (MeCP2) dysfunction on iPSC-derived neuronal migration and maturation (reduced neurite outgrowth and fewer synapses) in 3D layered hydrogels. Thus, this 3D system expands the range of neural phenotypes that can be studied in vitro to include those influenced by physical and mechanical stimuli or requiring specific arrangements of multiple cell types.3D hydrogels | neuronal migration and maturation | 3D RTT modeling N euronal migration and maturation is a key step in brain development. Defects in this process have been implicated in many disorders, including autism (1) and schizophrenia (2). Thoroughly understanding how neural progenitor cell (NPC) migration is affected in neurodevelopmental disorders requires a means of dissecting the process using cells with genetic alterations matching those in patients. Existing in vitro assays of migration generally involve measurement of cell movement across a scratch or gap or through a membrane toward a chemoattractant in 2D culture systems. Although widely used, such assays may not accurately reveal in vivo differences, as neuronal migration is tightly regulated by physical and chemical cues in the extracellular matrix (ECM) that NPCs encounter as they migrate.In vitro 3D culture systems offer a solution to these limitations (3-7). Compared with 2D culture, a 3D arrangement allows neuronal cells to interact with many more cells (4); this similarity to the in vivo setting has been shown to lengthen viability, enhance survival, and allow formation of longer neurites and more dense networks in primary neurons in uniform matrices or aggregate culture (8, 9). Indeed, 3D culture systems have been used to study nerve regeneration, neuronal and glial development (10-12), and amyloid-β and tau pathology (13). Thus, measuring neuronal migration through a soft 3D matrix would continue this trend toward using 3D systems to study neuronal development and pathology.We sought to develop a 3D assay to examine potential migration and neuronal maturation defects in Rett syndrome (RTT), a genetic neurodevelopmental disorder that affects 1 in 10,000 children in the United States and is caused by mutations in the X-linked methyl-CpG-binding protein-2 (MECP2) gene (14). Studies using induced pluripotent stem cells (iPSCs) from RTT patients in traditiona...

Methylation of the regulatory region of the elongation of very‐long‐chain fatty acids‐like 2 (ELOVL2) gene, an enzyme involved in elongation of long‐chain polyunsaturated fatty acids, is one of the most robust biomarkers of human age, but the critical question of whether ELOVL2 plays a functional role in molecular aging has not been resolved. Here, we report that Elovl2 regulates age‐associated functional and anatomical aging in vivo, focusing on mouse retina, with direct relevance to age‐related eye diseases. We show that an age‐related decrease in Elovl2 expression is associated with increased DNA methylation of its promoter. Reversal of Elovl2 promoter hypermethylation in vivo through intravitreal injection of 5‐Aza‐2’‐deoxycytidine (5‐Aza‐dc) leads to increased Elovl2 expression and rescue of age‐related decline in visual function. Mice carrying a point mutation C234W that disrupts Elovl2‐specific enzymatic activity show electrophysiological characteristics of premature visual decline, as well as early appearance of autofluorescent deposits, well‐established markers of aging in the mouse retina. Finally, we find deposits underneath the retinal pigment epithelium in Elovl2 mutant mice, containing components found in human drusen, a pathologic hallmark of age related macular degeneration. These findings indicate that ELOVL2 activity regulates aging in mouse retina, provide a molecular link between polyunsaturated fatty acids elongation and visual function, and suggest novel therapeutic strategies for the treatment of age‐related eye diseases.

Therapies for macular degeneration and diabetic retinopathy require intravitreal injections every 4-8 weeks. Injections are uncomfortable, time-consuming, and carry risks of infection and retinal damage. However, drug delivery via noninvasive methods to the posterior segment of the eye has been a major challenge due to the eye's unique anatomy and physiology. Here we present a novel nanoparticle depot platform for on-demand drug delivery using a far ultraviolet (UV) light-degradable polymer, which allows noninvasively triggered drug release using brief, low-power light exposure. Nanoparticles stably retain encapsulated molecules in the vitreous, and can release cargo in response to UV exposure up to 30 weeks post-injection. Light-triggered release of nintedanib (BIBF 1120), a small molecule angiogenesis inhibitor, 10 weeks post-injection suppresses choroidal neovascularization (CNV) in rats. Light-sensitive nanoparticles are biocompatible and cause no adverse effects on the eye as assessed by electroretinograms (ERG), corneal and retinal tomography, and histology.

Nanoparticle (NP) based exogenous contrast agents assist biomedical imaging by enhancing the target visibility against the background. However, it is challenging to design a single type of contrast agents that are simultaneously suitable for various imaging modalities. The simple integration of different components into a single NP contrast agent does not guarantee the optimized properties of each individual components. Herein, we describe lanthanide-based core–shell–shell (CSS) NPs as triple-modal contrast agents that have concurrently enhanced performance compared to their individual components in photoluminescence (PL) imaging, magnetic resonance imaging (MRI), and computed tomography (CT). The key to simultaneous enhancement of PL intensity, MRI r1 relaxivity, and X-ray attenuation capability in CT is tuning the interfacial layer in the CSS NP architecture. By increasing the thickness of the interfacial layer, we show that (i) PL intensity is enhanced from completely quenched/dark state to brightly emissive state of both upconversion and downshifting luminescence at different excitation wavelengths (980 and 808 nm), (ii) MRI r1 relaxivity is enhanced by 5-fold from 11.4 to 52.9 mM−1 s−1 (per Gd3+) at clinically relevant field strength 1.5 T, and (iii) the CT Hounsfield Unit gain is 70% higher than the conventional iodine-based agents at the same mass concentration. Our results demonstrate that judiciously designed contrast agents for multimodal imaging can achieve simultaneously enhanced performance compared to their individual stand-alone structures and highlight that multimodality can be achieved without compromising on individual modality performance.

Controlling chemistry in space and time has offered scientists and engineers powerful tools for research and technology. For example, on-demand photo-triggered activation of neurotransmitters has revolutionized neuroscience. Non-invasive control of the availability of bioactive molecules in living organisms will undoubtedly lead to major advances; however, this requires the development of photosystems that efficiently respond to regions of the electromagnetic spectrum that innocuously penetrate tissue. To this end, we have developed a polymer that photochemically degrades upon absorption of one photon of visible light and demonstrated its potential for medical applications. Particles formulated from this polymer release molecular cargo in vitro and in vivo upon irradiation with blue visible light through a photoexpansile swelling mechanism.

Paramagnetic gadolinium (Gd(3+))-based nanocrystals (NCs) with a large number of confined gadolinium ions can be expected to heavily enhance the longitudinal (T1) relaxation of water protons compared to clinical gadolinium complexes with only a single paramagnetic center. However, paramagnetic Gd(3+)-NCs reported to date show only a modest T1 relaxivity of ∼10 mM(-1) s(-1) per Gd(3+) at 1.5 T, only about 3-times higher than clinical Gd(3+) complexes. Here we demonstrate a strategy that achieves ultrahigh T1 relaxivity that is about 25-times higher than clinical Gd(3+) complexes by controlling the proximity of water protons to a paramagnetic NC surface. Using NaGdF4 NCs (∼3 nm) coated with PEG-ylated phospholipid (DSPE-PEG) micelles, we show that the distance of water protons to the NCs surface can be tuned by controlling the NC-micelle sizes. Increasing the ratio of DSPE-PEG to NCs during micellization decreases the size of NC-micelles, enhancing the proximity of water to the NC surface. Using this strategy, we have achieved compact NC-micelles (hydrodynamic diameter, HD ∼ 5 nm) with ultrahigh T1 relaxivity of ∼80 mM(-1) s(-1) per Gd(3+) at 1.41 T. The findings reported here demonstrate a nanostructured Gd(3+)-contrast agent (CA) that simultaneously achieves an ultrahigh T1 relaxivity approaching theoretical predictions, extremely compact size (HD < 5 nm), and a biocompatible surface. Our results show the hitherto unknown ultrahigh T1 relaxation enhancement of water protons in close proximity to a colloidal gadolinium-NC surface that is achievable by precise control of their surface structure.

Upconversion nanoparticles (UCNPs) are promising platforms to enhance the therapeutic response of cancer cells toward photodynamic therapy (PDT). When coupled with UCNPs, the photosensitizers in PDT are indirectly activated by near-infrared (NIR) excitation that allows for deeper tissue penetration and reduced attenuation. To achieve maximum performance, the upconverted emission peak of the UCNPs and absorption band of the photosensitizers need to overlap significantly. However, the spectral mismatch between the upconverted emission maximum of UCNPs (predominantly in the green) and absorption maximum of most available photosensitizers (in the red) greatly limits the therapeutic efficacy of current UCNP-PDT platforms. Here we report a UCNP-PDT platform that under biobenign 808 nm NIR excitation shows a strong spectral overlap between the UCNP emission (λem) and absorption of zinc phthalocyanine photosensitizers (λabs). The spectrally matched UCNP red emission band is 40 times stronger than the green emission band and is independent of laser excitation power across a wide range (0.6–3.4 W/cm2) applicable in biological systems. The spectrally matched UCNP-PDT platform enables rapid generation (5 min) of cytotoxic singlet oxygen via near-infrared excitation at extremely low laser power density of only 0.6 W/cm2. Finally, we show that the actively growing HeLa cancer cell spheroids with 3 mm diameter can be effectively suppressed with 65% drop of the cell viability, demonstrating the suitability and effectiveness of the spectrally matched UCNP-PDT platforms for cancer therapeutics.