Optical techniques used in medical diagnosis, surgery, and therapy require efficient and flexible delivery of light from light sources to target tissues. While this need is currently fulfilled by ...glass and plastic optical fibers, recent emergence of biointegrated approaches, such as optogenetics and implanted devices, calls for novel waveguides with certain biophysical and biocompatible properties and desirable shapes beyond what the conventional optical fibers can offer. To this end, exploratory efforts have begun to harness various transparent biomaterials to develop waveguides that can serve existing applications better and enable new applications in future photomedicine. Here, the recent progress in this new area of research for developing biomaterial‐based optical waveguides is reviewed. It begins with a survey of biological light‐guiding structures found in plants and animals, a source of inspiration for biomaterial photonics engineering. The review then describes natural and synthetic polymers and hydrogels that offer appropriate optical properties, biocompatibility, biodegradability, and mechanical flexibility have been exploited for light‐guiding applications. Finally, perspectives on biomedical applications that may benefit from the unique properties and functionalities of light‐guiding biomaterials are discussed briefly.
A review on light‐guiding biomaterials for biomedical applications is provided. Some new medical applications, including diagnostics, drug delivery, phototherapy, optogenetic, and wearable optical devices and sensors require novel optical waveguides with specific optical, mechanical, and biological properties. Various natural and synthetic materials are developed to meet such requirements.
Optical microresonators
which confine light within a small cavity are widely exploited for various applications ranging from the realization of lasers
and nonlinear devices
to biochemical and ...optomechanical sensing
. Here we employ microresonators and suitable optical gain materials inside biological cells to demonstrate various optical functions
including lasing. We explored two distinct types of microresonators: soft and hard, that support whispering-gallery modes (WGM). Soft droplets formed by injecting oil or using natural lipid droplets support intracellular laser action. The laser spectra from oil-droplet microlasers can chart cytoplasmic internal stress (~500 pN/μm
) and its dynamic fluctuations at a sensitivity of 20 pN/μm
(20 Pa). In a second form, WGMs within phagocytized polystyrene beads of different sizes enable individual tagging of thousands of cells easily and, in principle, a much larger number by multiplexing with different dyes.
A biocompatible step‐index optical fiber made of poly(ethylene glycol) and alginate hydrogels is demonstrated. The fabricated fiber exhibits excellent light‐guiding efficiency in biological tissues. ...Moreover, the core of hydrogel fibers can be easily doped with functional molecules and nanoparticles for localized light emission, sensing, and therapy.
Optofluidic biolasers are emerging as a highly sensitive way to measure changes in biological molecules. Biolasers, which incorporate biological material into the gain medium and contain an optical ...cavity in a fluidic environment, can use the amplification that occurs during laser generation to quantify tiny changes in biological processes in the gain medium. We describe the principle of the optofluidic biolaser, review recent progress and provide our outlooks on potential applications and directions for developing this technology.
A core‐clad fiber made of elastic, tough hydrogels is highly stretchable while guiding light. Fluorescent dyes are easily doped into the hydrogel fiber by diffusion. When stretched, the transmission ...spectrum of the fiber is altered, enabling the strain to be measured and also its location.
Acoustic wave velocity measurement based on optical coherence tomography (OCT) is a promising approach to assess the mechanical properties of biological tissues and soft materials. While studies to ...date have demonstrated proof of concept of different ways to excite and detect mechanical waves, the quantitative performance of this modality as mechanical measurement has been underdeveloped. Here, we investigate the frequency dependent measurement of the wave propagation in viscoelastic tissues, using a piezoelectric point-contact probe driven with various waveforms. We found that a frequency range of 2-10 kHz is a good window for corneal elastography, in which the lowest-order flexural waves can be identified in post processing. We tested our system on tissue-simulating phantoms and ex vivo porcine eyes, and demonstrate reproducibility and inter-sample variability. Using the Kelvin-Voigt model of viscoelasticity, we extracted the shear-elastic modulus and viscosity of the cornea and their correlation with the corneal thickness, curvature, and eyeball mass. Our results show that our method can be a quantitative, useful tool for the mechanical analysis of the cornea.
Calf diarrhea is associated with enteric infections, and also provokes the overuse of antibiotics. Therefore, proper treatment of diarrhea represents a therapeutic challenge in livestock production ...and public health concerns. Here, we describe the ability of a fecal microbiota transplantation (FMT), to ameliorate diarrhea and restore gut microbial composition in 57 growing calves. We conduct multi-omics analysis of 450 longitudinally collected fecal samples and find that FMT-induced alterations in the gut microbiota (an increase in the family Porphyromonadaceae) and metabolomic profile (a reduction in fecal amino acid concentration) strongly correlate with the remission of diarrhea. During the continuous follow-up study over 24 months, we find that FMT improves the growth performance of the cattle. This first FMT trial in ruminants suggest that FMT is capable of ameliorating diarrhea in pre-weaning calves with alterations in their gut microbiota, and that FMT may have a potential role in the improvement of growth performance.
Hydrogel optical fibers are utilized for continuous glucose sensing in real time. The hydrogel fibers consist of poly(acrylamide‐co‐poly(ethylene glycol) diacrylate) cores functionalized with ...phenylboronic acid. The complexation of the phenylboronic acid and cis‐diol groups of glucose enables reversible changes of the hydrogel fiber diameter. The analyses of light propagation loss allow for quantitative glucose measurements within the physiological range.
While photoluminescent graphene quantum dots (GQDs) have long been considered very suitable for bioimaging owing to their protein‐like size, superhigh photostability and in vivo long‐term biosafety, ...their unique and crucial bioimaging applications in vivo remain unreachable. Herein, planted GQDs are presented as an excellent tool for in vivo fluorescent, sustainable and multimodality tumor bioimaging in various scenarios. The GQDs are in situ planted in the poly(ethylene glycol) (PEG) layer of PEGylated nanoparticles via a bottom‐up molecular approach to obtain the NPs‐GQDs‐PEG nanocomposite. The planted GQDs show more than four times prolonged blood circulation and 7–8 times increased tumor accumulation than typical GQDs in vivo. After accessible specificity modification, the multifunctional NPs‐GQDs‐PEG provides targeted, multimodal molecular imaging for various tumor models in vitro or in vivo. Moreover, the highly photostable GQDs enable long‐term, real‐time visualization of the local pharmacokinetics of NPs in vivo. Planting GQDs in PEGylated nanomedicine offers a new strategy for broad in vivo biomedical applications of GQDs.
Graphene quantum dots (GQDs) are in situ planted in a poly(ethylene glycol) (PEG) layer of PEGylated nanoparticles from small‐molecule pyrene. After accessible specificity modification, the multifunctional NPs‐GQDs‐PEG provides targeted, multimodal molecular imaging for various tumor models in vitro or in vivo. Moreover, the highly photostable GQDs enable long‐term, real‐time visualization of the local pharmacokinetics of NPs in vivo.
The planar spin glass pattern is widely known for its inherent randomness, resulting from the geometrical frustration. As such, developing physical unclonable functions (PUFs)—which operate with ...device randomness—with planar spin glass patterns is a promising candidate for an advanced security systems in the upcoming digitalized society. Despite their inherent randomness, traditional magnetic spin glass patterns pose considerable obstacles in detection, making it challenging to achieve authentication in security systems. This necessitates the development of facilely observable mimetic patterns with similar randomness to overcome these challenges. Here, a straightforward approach is introduced using a topologically protected maze pattern in the chiral liquid crystals (LCs). This maze exhibits a comparable level of randomness to magnetic spin glass and can be reliably identified through the combination of optical microscopy with machine learning‐based object detection techniques. The “information” embedded in the maze can be reconstructed through thermal phase transitions of the LCs in tens of seconds. Furthermore, incorporating various elements can enhance the optical PUF, resulting in a multi‐factor security medium. It is expected that this security medium, based on microscopically controlled and macroscopically uncontrolled topologically protected structures, may be utilized as a next‐generation security system.
The deterministic and non‐deterministic properties of a topologically protected maze in the chiral liquid crystal (LC) resulting from microscopic order and macroscopic disorder accomplish a security system that serves as advanced artificial fingerprints. This system enables facile authentication through deep‐learning technology and can reconstruct information through the phase transition of LCs.
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