Explore the vast range of titles available.

Light penetration depth, as a characteristic parameter reflecting light attenuation and transmission in biological tissues, has been applied in nondestructive detection of fruits and vegetables. Recently, with emergence of new optical detection technologies, researchers have begun to explore methods evaluating optical properties of double-layer or even multilayer fruit and vegetable tissues due to the differences between peel and pulp in the chemical composition and physical properties, which has gradually promoted studies on light penetration depth. A series of demonstrated research on light penetration depth could ensure the accuracy of the optical information obtained from each layer of tissue, which is beneficial to enhance detection accuracy for quality assessment of fruits and vegetables. Therefore, the aim of this review is to give detailed outlines about the theory and principle of light penetration depth based on several emerging optical detection technologies and to focus primarily on its applications in the field of quality evaluation of fruits and vegetables, its future applicability in fruits and vegetables and the challenges it may face in the future.

Spatial-frequency domain imaging (SFDI) has been developed as an emerging modality for detecting early-stage bruises of fruits, such as apples, due to its unique advantage of a depth-resolved imaging feature. This paper presents theoretical and experimental analyses to determine the light penetration depth in apple tissues under spatially modulated illumination. Simulation and practical experiments were then carried out to explore the maximum light penetration depths in ‘Golden Delicious’ apples. Then, apple experiments for early-stage bruise detection using the estimated reduced scattering coefficient mapping were conducted to validate the results of light penetration depths. The results showed that the simulations produced comparable or a little larger light penetration depth in apple tissues (~2.2 mm) than the practical experiment (~1.8 mm or ~2.3 mm). Apple peel further decreased the light penetration depth due to the high absorption properties of pigment contents. Apple bruises located beneath the surface peel with the depth of about 0–1.2 mm could be effectively detected by the SFDI technique. This study, to our knowledge, made the first effort to investigate the light penetration depth in apple tissues by SFDI, which would provide useful information for enhanced detection of early-stage apple bruising by selecting the appropriate spatial frequency.

Owing to the poor penetration depth of light, phototherapy, including photothermal and photodynamic therapies, remains severely ineffective in treating deep tissue infections such as methicillin-resistant Staphylococcus aureus (MRSA)-infected osteomyelitis. Here, we report a microwave-excited antibacterial nanocapturer system for treating deep tissue infections that consists of microwave-responsive Fe 3 O 4 /CNT and the chemotherapy agent gentamicin (Gent). This system, Fe 3 O 4 /CNT/Gent, is proven to efficiently target and eradicate MRSA-infected rabbit tibia osteomyelitis. Its robust antibacterial effectiveness is attributed to the precise bacteria-capturing ability and magnetic targeting of the nanocapturer, as well as the subsequent synergistic effects of precise microwaveocaloric therapy from Fe 3 O 4 /CNT and chemotherapy from the effective release of antibiotics in infection sites. The advanced target-nanocapturer of microwave-excited microwaveocaloric-chemotherapy with effective targeting developed in this study makes a major step forward in microwave therapy for deep tissue infections. Deep tissue infections can be difficult to treat due to limited light penetration associated with phototherapies. Here, the authors report on a bacterial capture system for antibiotic delivery and microwave-assisted killing of MRSA in osteomyelitis and demonstrate application in vivo.

Photodynamic therapy (PDT) is a cancer treatment with strong potential over well-established standard therapies in certain cases. Non-ionising radiation, localisation, possible repeated treatments, and stimulation of immunological response are some of the main beneficial features of PDT. Despite the great potential, its application remains challenging. Limited light penetration depth, non-ideal photosensitisers, complex dosimetry, and complicated implementations in the clinic are some limiting factors hindering the extended use of PDT. To surpass actual technological paradigms, radically new sources, light-based devices, advanced photosensitisers, measurement devices, and innovative application strategies are under extensive investigation. The main aim of this review is to highlight the advantages/pitfalls, technical challenges and opportunities of PDT, with a focus on technologies for light activation of photosensitisers, such as light sources, delivery devices, and systems. In this vein, a broad overview of the current status of superficial, interstitial, and deep PDT modalities—and a critical review of light sources and their effects on the PDT process—are presented. Insight into the technical advancements and remaining challenges of optical sources and light devices is provided from a physical and bioengineering perspective.

Photomedicine has gained great attention due to its nontoxicity, good selectivity and small trauma. However, owing to the limited penetration of light and difficult monitoring of the photo-media therapies, it is challenging to apply photomedical treatment in deep tissue as they may damage normal tissues. Herein, a thermal regulated interventional photomedicine based on a temperature-adaptive hydrogel fiber-based optical waveguide (THFOW) is proposed, capable of eliminating deeply seated tumor cells while lowering risks of overtemperature (causes the death of healthy cells around the tumor). The THFOW is fabricated by an integrated homogeneous-dynamic-crosslinking-spinning method, and shows a remarkable soft tissue-affinity (low cytotoxicity, swelling stability, and soft tissue-like Young’s modulus). Moreover, the THFOW shows an excellent light propagation property with different wavenumbers (especially −0.32 dB cm −1 with 915 nm laser light), and temperature-gated light propagation effect. The THFOW and relevant therapeutic strategy offer a promising application for intelligent photomedicine in deep issue. Light penetration and overheating are major issues facing the application of photothermal therapy. Here, the authors develop a temperature responsive hydrogel optical waveguide for controlled delivery of light to deep tumours and demonstrate biocompatibility and temperature responsive phototherapy in vivo

Brain photobiomodulation (PBM) therapy using red to near-infrared (NIR) light is an innovative treatment for a wide range of neurological and psychological conditions. Red/NIR light is able to stimulate complex IV of the mitochondrial respiratory chain (cytochrome c oxidase) and increase ATP synthesis. Moreover, light absorption by ion channels results in release of Ca2+ and leads to activation of transcription factors and gene expression. Brain PBM therapy enhances the metabolic capacity of neurons and stimulates anti-inflammatory, anti-apoptotic, and antioxidant responses, as well as neurogenesis and synaptogenesis. Its therapeutic role in disorders such as dementia and Parkinson’s disease, as well as to treat stroke, brain trauma, and depression has gained increasing interest. In the transcranial PBM approach, delivering a sufficient dose to achieve optimal stimulation is challenging due to exponential attenuation of light penetration in tissue. Alternative approaches such as intracranial and intranasal light delivery methods have been suggested to overcome this limitation. This article reviews the state-of-the-art preclinical and clinical evidence regarding the efficacy of brain PBM therapy.

While vat photopolymerization has many advantages over soft lithography in fabricating microfluidic devices, including efficiency and shape complexity, it has difficulty achieving well-controlled micrometer-sized (smaller than 100 μm) channels in the layer building direction. The considerable light penetration depth of transparent resin leads to over-curing that inevitably cures the residual resin inside flow channels, causing clogs. In this paper, a 3D printing process — in-situ transfer vat photopolymerization is reported to solve this critical over-curing issue in fabricating microfluidic devices. We demonstrate microchannels with high Z -resolution (within 10 μm level) and high accuracy (within 2 μm level) using a general method with no requirements on liquid resins such as reduced transparency nor leads to a reduced fabrication speed. Compared with all other vat photopolymerization-based techniques specialized for microfluidic channel fabrication, our universal approach is compatible with commonly used 405 nm light sources and commercial photocurable resins. The process has been verified by multifunctional devices, including 3D serpentine microfluidic channels, microfluidic valves, and particle sorting devices. This work solves a critical barrier in 3D printing microfluidic channels using the high-speed vat photopolymerization process and broadens the material options. It also significantly advances vat photopolymerization’s use in applications requiring small gaps with high accuracy in the Z -direction. Despite many advantages of vat photopolymerization in microfluidic device fabrication, well-controlled μm-sized (< 100 μm) channels in the layer building direction remains a challenge. Here, authors present a general high resolution and low-cost 3D printing process that can produce devices within the 10 μm scale.

Although we have made great strides in treating deadly diseases over the years, cancer therapy still remains a daunting challenge. Among numerous anticancer methods, photodynamic therapy (PDT), a non-invasive therapeutic approach, has attracted much attention. PDT exhibits outstanding performance in cancer therapy, but some unavoidable disadvantages, including limited light penetration depth, poor tumor selectivity, as well as oxygen dependence, largely limit its therapeutic efficiency for solid tumors treatment. Thus, numerous strategies have gone into overcoming these obstacles, such as exploring new photosensitizers with higher photodynamic conversion efficiency, alleviating tumor hypoxia to fuel the generation of reactive oxygen species (ROS), designing tumor-targeted PS, and applying PDT-based combination strategies. In this review, we briefly summarized the PDT related tumor therapeutic approaches, which are mainly characterized by advanced PSs, these PSs have excellent conversion efficiency and additional refreshing features. We also briefly summarize PDT-based combination therapies with excellent therapeutic effects.

Optically transparent wood has been fabricated by structure-retaining delignification of wood and subsequent infiltration of thermo- or photocurable polymer resins but still limited by the intrinsic low mesopore volume of the delignified wood. Here we report a facile approach to fabricate strong transparent wood composites using the wood xerogel which allows solvent-free infiltration of resin monomers into the wood cell wall under ambient conditions. The wood xerogel with high specific surface area (260 m 2  g –1 ) and high mesopore volume (0.37 cm 3  g –1 ) is prepared by evaporative drying of delignified wood comprising fibrillated cell walls at ambient pressure. The mesoporous wood xerogel is compressible in the transverse direction and provides precise control of the microstructure, wood volume fraction, and mechanical properties for the transparent wood composites without compromising the optical transmittance. Transparent wood composites of large size and high wood volume fraction (50%) are successfully prepared, demonstrating potential scalability of the method. Optically transparent wood composites are commonly prepared by delignification of wood and subsequent infiltration of thermo- or photocurable polymer resins but the fabrication is still limited by the intrinsic low mesopore volume of the delignified wood. Here, the authors report a facile approach to fabricate transparent wood using wood xerogel which allows solvent-free infiltration of resin monomers into the wood cell wall under ambient conditions.’

Browning of surface waters, as a result of increasing dissolved organic carbon and iron concentrations, is a widespread phenomenon with implications to the structure and function of aquatic ecosystems. In this article, we provide an overview of the consequences of browning in relation to ecosystem services, outline what the underlying drivers and mechanisms of browning are, and specifically focus on exploring potential mitigation measures to locally counteract browning. These topical concepts are discussed with a focus on Scandinavia, but are of relevance also to other regions. Browning is of environmental concern as it leads to, e.g., increasing costs and risks for drinking water production, and reduced fish production in lakes by limiting light penetration. While climate change, recovery from acidification, and land-use change are all likely factors contributing to the observed browning, managing the land use in the hydrologically connected parts of the landscape may be the most feasible way to counteract browning of natural waters.