Advances of NIR Light Responsive Materials for Diagnosis and Treatment of Brain Diseases

Abstract

Generally, brain diseases could be classified into various types. [2] The first is brain tumors, such as malignant glioblastoma, which grows invasively and destroys deep structures. The second type is brain trauma, i.e., traumatic brain injury (TBI), [3] which could cause multiple secondary injuries, including neuroinflammation, blood brain barrier (BBB) damage, and brain edema. The brain vascular diseases are an important type of brain diseases, such as strokes, which can induce a range of dysfunction due to the severe damage to the motor and sensory central nervous system (CNS). Besides, neurodegenerative diseases such as Alzheimer's disease (AD) can result in an irreversible damage to brain tissues owing to the loss of neurons and myelin sheath over time. However, due to the unclear pathogenesis and the obstacle of BBB in CNS, precise imaging diagnosis and effective therapy of brain diseases still remain a great challenge till now. [4] Hence, it is an urgent need to develop the noninvasive, efficient, and convenient techniques for precise imaging and effective therapy of brain diseases. In recent years, the optical materials have attracted great attention in the field of bioapplications, [5] but the limited penetration depth of common used excitation lights (ultraviolet or visible lights, UV-Vis) leads to their applications only in some superficial diseases, such as skin or oral tumors. [6] Currently, it has been reported that the near infrared (NIR) lights exhibit much deeper tissue penetration depth than that of UV-Vis lights, [7] especially penetrate the skull, which makes them possible for imaging and therapy of brain diseases. Hence, exploring NIR light responsive materials is a promising way for achieving precise diagnosis and efficient therapy of brain diseases. [8,9] In terms of imaging, photoacoustic (PA) imaging and the fluorescence imaging are the major imaging techniques responding to NIR lights. PA imaging integrates the advantages of NIR light and ultrasound, achieving biological imaging with deep tissue penetration depth (≈6 cm) and high contrast and resolution. [10] Besides, the lower scattering and autofluorescence of tissues in NIR region endow NIR fluorescence imaging with high sensitivity and signal-to-noise ratio (SNR). [11,12] Indocyanine green (ICG), a NIR molecule dye, was used as NIR fluorescence imaging probe in 1955 and approved by Food and Drug Administration (FDA) for clinic in 1959, but it suffered from the poor photostability and short blood circulation.

Virus-mimicking nanosystems: from design to biomedical applications

“…By mimicking the rabies virus, Lee et al successfully developed unique silica-coated gold nanorods (RVG-PEG-AuNRs@SiO 2 ) that can penetrate the blood–brain barrier, advancing the diagnosis and treatment of brain diseases. 67 Following the Covid-19 outbreak, nanomaterials that mimic SARS-CoV-2 tissue tropism have also been efficiently delivered to specific tissues or cells, which can efficiently improve the accuracy of diagnosis or the potency of drugs. 68,69…”

Light-driven micro/nanomotors in biomedical applications

“…NIR light has good biological safety and high tissue penetration, which makes it more suitable for deep tissue penetration applications. 184,185 Besides, appropriate light sources are selected according to different parts of the organism. (1) Irradiating light-responsive MNMs with NIR-I/ NIR-II wavelengths have been used to penetrate deep tissue regions for excellent disease treatment.…”

A novel polymer enabled by polymerized small molecule strategy for tumor photothermal and photodynamic therapy

“…Therefore, Scheme 1 PYT enabled by polymerized small molecule strategy for tumor photothermal and photodynamic therapy organic materials are the best candidates for large-scale clinical application in the future, which has attracted more and more researchers' attention. Currently, the U.S. Food and Drug Administration (FDA) has approved indocyanine green (ICG) for clinical application, which is a typical example [15]. However, due to ICG inferior photothermal conversion efficiency and optical instability, the application of ICG is limited obviously.…”