Recent progress in shape memory polymer: New behavior, enabling materials, and mechanistic understanding

Significance: Fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to distinguish the unique molecular environment of fluorophores. FLIM measures the time a fluorophore remains in an excited state before emitting a photon, and detects molecular variations of fluorophores that are not apparent with spectral techniques alone. FLIM is sensitive to multiple biomedical processes including disease progression and drug efficacy.
Aim: We provide an overview of FLIM principles, instrumentation, and analysis while highlighting the latest developments and biological applications.
Approach: This review covers FLIM principles and theory, including advantages over intensity-based fluorescence measurements. Fundamentals of FLIM instrumentation in time- and frequency-domains are summarized, along with recent developments. Image segmentation and analysis strategies that quantify spatial and molecular features of cellular heterogeneity are reviewed. Finally, representative applications are provided including high-resolution FLIM of cell- and organelle-level molecular changes, use of exogenous and endogenous fluorophores, and imaging protein-protein interactions with Forster resonance energy transfer (FRET). Advantages and limitations of FLIM are also discussed.
Conclusions: FLIM is advantageous for probing molecular environments of fluorophores to inform on fluorophore behavior that cannot be elucidated with intensity measurements alone. Development of FLIM technologies, analysis, and applications will further advance biological research and clinical assessments.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-25/issue-7/071203/Fluorescence-lifetime-imaging-microscopy--fundamentals-and-advances-in-instrumentation/10.1117/1.JBO.25.7.071203.pdf

Fluorescence lifetime imaging microscopy: fundamentals and advances in instrumentation, analysis, and applications

Advances in healing-on-demand polymers and polymer composites

https://digital.library.unt.edu/ark:/67531/metadc869929/m2/1/high_res_d/1122211.pdf

Low density biodegradable shape memory polyurethane foams for embolic biomedical applications.

Delivery of growth factors using a smart porous nanocomposite scaffold to repair a mandibular bone defect.

This paper presents the use and characterization of an electrically focus tunable lens to perform axial scanning in a confocal microscope Lateral and axial resolution are characterized over a >250 µm axial scan range Confocal microscopy using optical axial scanning is demonstrated in epithelial tissue and compared to traditional stage scanning By enabling rapid axial scanning, minimizing motion artifacts, and reducing mechanical complexity, this technique has potential to enhance in vivo three-dimensional imaging in confocal endomicroscopy

Optical axial scanning in confocal microscopy using an electrically tunable lens.

Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use.

/pdf/porous-shape-memory-polymers-8knimcydq4.pdf

Porous Shape Memory Polymers

We present a novel chromatic confocal microscope capable of volumetric reflectance imaging of microstructure in non-transparent tissue. Our design takes advantage of the chromatic aberration of aspheric lenses that are otherwise well corrected. Strong chromatic aberration, generated by multiple aspheres, longitudinally disperses supercontinuum light onto the sample. The backscattered light detected with a spectrometer is therefore wavelength encoded and each spectrum corresponds to a line image. This approach obviates the need for traditional axial mechanical scanning techniques that are difficult to implement for endoscopy and susceptible to motion artifact. A wavelength range of 590-775 nm yielded a >150 µm imaging depth with ~3 µm axial resolution. The system was further demonstrated by capturing volumetric images of buccal mucosa. We believe these represent the first microstructural images in non-transparent biological tissue using chromatic confocal microscopy that exhibit long imaging depth while maintaining acceptable resolution for resolving cell morphology. Miniaturization of this optical system could bring enhanced speed and accuracy to endomicroscopic in vivo volumetric imaging of epithelial tissue.

Chromatic confocal microscopy for multi-depth imaging of epithelial tissue.

We present a mechanical-scan-free method for volumetric imaging of biological tissue. The optical sectioning is provided by structured illumination, and the depth of the imaging plane is varied using an electrically tunable-focus lens. We characterize and evaluate the ability of this axial-scanning mechanism in structured illumination microscopy and demonstrate its ability to perform subcellular resolution imaging in oral mucosa ex vivo. The proposed mechanism can potentially convert any wide-field microscope to a 3D-imaging platform without the need for mechanical scanning of imaging optics and/or sample.

/pdf/volumetric-structured-illumination-microscopy-enabled-by-a-4ubjo7wy5j.pdf

Volumetric structured illumination microscopy enabled by a tunable-focus lens

A reflectance confocal endomicroscope with double-clad fiber coupler and electrically tunable focus lens is applied to imaging of the oral mucosa. The instrument is designed to be lightweight and robust for clinical use. The tunable lens allows axial scanning through > 250 ?? ? m in the epithelium when the probe tip is placed in contact with tissue. Images are acquired at 6.6 frames per second with a field of view diameter up to 850 ?? ? m . In vivo imaging of a wide range of normal sites in the oral cavity demonstrates the accessibility of the handheld probe. In vivo imaging of clinical lesions diagnosed as inflammation and dysplasia illustrates the ability of reflectance confocal endomicroscopy to image cellular changes associated with pathology.

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-22/issue-5/056008/----Custom-HTML----Handheld/10.1117/1.JBO.22.5.056008.pdf

Cory Olsovsky

Papers

Optical axial scanning in confocal microscopy using an electrically tunable lens.

Porous Shape Memory Polymers

Chromatic confocal microscopy for multi-depth imaging of epithelial tissue.

Volumetric structured illumination microscopy enabled by a tunable-focus lens

Handheld tunable focus confocal microscope utilizing a double-clad fiber coupler for in vivo imaging of oral epithelium.