Line-scanning confocal microscopy for high-resolution imaging of upconverting rare-earth-based contrast agents

Surface-Modified Shortwave-Infrared-Emitting Nanophotonic Reporters for Gene-Therapy Applications

Gene therapy is emerging as the next generation of therapeutic modality with United States Food and Drug Administration approved gene-engineered therapy for cancer and a rare eye-related disorder, but the challenge of real-time monitoring of on-target therapy response remains. In this study, we have designed a theranostic nanoparticle composed of shortwave-infrared-emitting rare-earth-doped nanoparticles (RENPs) capable of delivering genetic cargo and of real-time response monitoring. We showed that the cationic coating of RENPs with branched polyethylenimine (PEI) does not have a significant impact on cellular toxicity, which can be further reduced by selectively modifying the surface characteristics of the PEI coating using counter-ions and expanding their potential applications in photothermal therapy. We showed the tolerability and clearance of a bolus dose of RENPs@PEI in mice up to 7 days after particle injection in addition to the RENPs@PEI ability to distinctively discern lung tumor lesions in a breast cancer mouse model with an excellent signal-to-noise ratio. We also showed the availability of amine functional groups in the collapsed PEI chain conformation on RENPs, which facilitates the loading of genetic cargo that hybridizes with target gene in an in vitro cancer model. The real-time monitoring and delivery of gene therapy at on-target sites will enable the success of an increased number of gene- and cell-therapy products in clinical trials.

Redox-Magnetohydrodynamically Controlled Fluid Flow with Poly(3,4-ethylenedioxythiophene) Coupled to an Epitaxial Light Sheet Confocal Microscope for Image Cytometry Applications

We present the merging of two technologies to perform continuous high-resolution fluorescence imaging of cellular suspensions in a deep microfluidics chamber with no moving parts. An epitaxial light sheet confocal microscope (e-LSCM) was used to image suspensions enabled by fluid transport via redox-magnetohydrodynamics (R-MHD). The e-LSCM features a linear solid state sensor, oriented perpendicular to the direction of flow, that can bin the emission across different numbers of pixels, yielding electronically adjustable optical sectioning. This, in addition to intensity thresholding, defines the axial resolution, which was validated with an optical phantom of polystyrene microspheres suspended in agarose. The linear fluid speed within the microfluidics chamber was uniform (0.16-2.9%) across the 0.5-1.0 mm lateral field of view (dependent upon the chosen magnification) with continuous acquisition. Also, the camera's linear exposure periods were controlled to ensure an accurate image aspect ratio across this span. Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrodeposited as an immobilized redox film on electrodes of a chip for R-MHD, and the fluid flow was calibrated to specific linear speeds as a function of applied current. Images of leukocytes stained with acridine orange, a fluorescent, amphipathic vital dye that intercalates DNA, were acquired in the R-MHD microfluidics chamber with the e-LSCM to demonstrate imaging of biological samples. The combination of these technologies provides a miniaturizable platform for large sample volumes and high-throughput, image-based analysis without the requirement of moving parts, enabling development of robust, point-of-care image cytometry.

Multiscale optical imaging of rare-earth-doped nanocomposites in a small animal model

Rare-earth-doped nanocomposites have appealing optical properties for use as biomedical contrast agents, but few systems exist for imaging these materials. We describe the design and characterization of (i) a preclinical system for whole animal in vivo imaging and (ii) an integrated optical coherence tomography/confocal microscopy system for high-resolution imaging of ex vivo tissues. We demonstrate these systems by administering erbium-doped nanocomposites to a murine model of metastatic breast cancer. Short-wave infrared emissions were detected in vivo and in whole organ imaging ex vivo. Visible upconversion emissions and tissue autofluorescence were imaged in biopsy specimens, alongside optical coherence tomography imaging of tissue microstructure. We anticipate that this work will provide guidance for researchers seeking to image these nanomaterials across a wide range of biological models.

Intrinsic optical sectioning with upconverting nanoparticles

Scanning laser upconversion microscopy yields true multiphoton sectioning power at very low excitation densities.

Widefield imaging of upconverting nanoparticles on epifluorescence microscopes adapted for laser illumination with top-hat profile

We describe a modification of epifluorescence microscopes that allows quantitative widefield imaging of samples labeled by upconverting nanoparticles (UCNP). A top-hat illumination profile on the sample was achieved with a 980-nm laser diode by using tandem microlens arrays, a moving diffuser and a telescope, which adjusts the top-hat area to the field of view. Illumination homogeneity is a critical factor for imaging of UCNP since the intensity of their luminescence typically scales with the second power of the excitation intensity. Our illuminator is combined with the epifluorescence attachment of the microscope, allowing easy switching between observation of UCNP and traditional fluorescent dyes. Illumination profile homogeneity of about 98% was measured for objectives with magnification from 4× to 100×, and the top-hat profile was also obtained with phase contrast objectives. We demonstrate capability of the illuminator by evaluating in vitro uptake of UCNP encapsulated in oleyl-hyaluronan micelles into breast cancer cells. Micelles bearing the targeting peptide were about an order of magnitude more efficient than nontargeted micelles.