Gold Nanocages: Engineering Their Structure for Biomedical Applications

The galvanic replacement reaction between a Ag template and HAuCl₄ in an aqueous solution transforms 30–200 nm Ag nanocubes into Au nanoboxes and nanocages (nanoboxes with porous walls). By controlling the molar ratio of Ag to HAuCl₄, the extinction peak of resultant structures can be continuously tuned from the blue (400 nm) to the near‐infrared (1200 nm) region of the electromagnetic spectrum. These hollow Au nanostructures are characterized by extraordinarily large cross‐sections for both absorption and scattering. Optical coherence tomography measurements indicate that the 36 nm nanocage has a scattering cross‐section of ～ 0.8 × 10^–15 m² and an absorption cross‐section of ～ 7.3 × 10^–15 m². The absorption cross‐section is more than five orders of magnitude larger than those of conventional organic dyes. Exposure of Au nanocages to a camera flash resulted in the melting and conversion of Au nanocages into spherical particles due to photothermal heating. Discrete‐dipole‐approximation calculations suggest that the magnitudes of both scattering and absorption cross‐sections of Au nanocages can be tailored by controlling their dimensions, as well as the thickness and porosity of their walls. This novel class of hollow nanostructures is expected to find use as both a contrast agent for optical imaging in early stage tumor detection and as a therapeutic agent for photothermal cancer treatment.     

Gold Nanozymes:From Concept to Biomedical Applications

In recent years,gold nanoparticles have demonstrated excellent enzyme-mimicking activities which resemble those of peroxidase,oxidase,catalase,superoxide dismutase or reductase.This,merged with their ease of synthesis,tunability,biocompatibility and low cost,makes them excellent candidates when compared with biological enzymes for applications in biomedicine or biochemical analyses.Herein,over 200 research papers have been systematically reviewed to present the recent progress on the fundamentals of gold nanozymes and their potential applications.The review reveals that the morphology and surface chemistry of the nanoparticles play an important role in their catalytic properties,as well as external parameters such as pH or temperature.Yet,real applications often require specific biorecognition elements to be immobilized onto the nanozymes,leading to unexpected positive or negative effects on their activity.Thus,rational design of efficient nanozymes remains a challenge of paramount importance.Different implementation paths have already been explored,including the application of peroxidase-like nanozymes for the development of clinical diagnostics or the regulation of oxidative stress within cells via their catalase and superoxide dismutase activities.The review also indicates that it is essential to understand how external parameters may boost or inhibit each of these activities,as more than one of them could coexist.Likewise,further toxicity studies are required to ensure the applicability of gold nanozymes in vivo.Current challenges and future prospects of gold nanozymes are discussed in this review,whose significance can be anticipated in a diverse range of fields beyond biomedicine,such as food safety,environmental analyses or the chemical industry.     

Dendritic Polyglycerols for Biomedical Applications

The application of nanotechnology in medicine and pharmaceuticals is a rapidly advancing field that is quickly gaining acceptance and recognition as an independent area of research called “nanomedicine”. Urgent needs in this field, however, are biocompatible and bioactive materials for antifouling surfaces and nanoparticles for drug delivery. Therefore, extensive attention has been given to the design and development of new macromolecular structures. Among the various polymeric architectures, dendritic (“treelike”) polymers have experienced an exponential development due to their highly branched, multifunctional, and well‐defined structures. This Review describes the diverse syntheses and biomedical applications of dendritic polyglycerols (PGs). These polymers exhibit good chemical stability and inertness under biological conditions and are highly biocompatible. Oligoglycerols and their fatty acid esters are FDA‐approved and are already being used in a variety of consumer applications, e.g., cosmetics and toiletries, food industries, cleaning and softening agents, pharmaceuticals, polymers and polymer additives, printing photographing materials, and electronics. Herein, we present the current status of dendritic PGs as functional dendritic architectures with particular focus on their application in nanomedicine, in drug, dye, and gene delivery, as well as in regenerative medicine in the form of non‐fouling surfaces and matrix materials.     

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed‐mediated chemical growth. In particular, we describe nanorod spontaneous self‐assembly, chemically driven assembly, and polymer‐based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.     

Molecularly Imprinted Nanoparticles for Biomedical Applications

Molecularly imprinted polymers (MIPs) are synthetic receptors with tailor-made recognition sites for target molecules. Their high affinity and selectivity, excellent stability, easy preparation, and low cost make them promising substitutes to biological receptors in many applications where molecular recognition is important. In particular, spherical MIP nanoparticles (or nanoMIPs) with diameters typically below 200 nm have drawn great attention because of their high surface-area-to-volume ratio, easy removal of templates, rapid binding kinetics, good dispersion and handling ability, undemanding functionalization and surface modification, and their high compatibility with various nanodevices and in vivo biomedical applications. Recent years have witnessed significant progress made in the preparation of advanced functional nanoMIPs, which has eventually led to the rapid expansion of the MIP applications from the traditional separation and catalysis fields to the burgeoning biomedical areas. Here, a comprehensive overview of key recent advances made in the preparation of nanoMIPs and their important biomedical applications (including immunoassays, drug delivery, bioimaging, and biomimetic nanomedicine) is presented. The pros and cons of each synthetic strategy for nanoMIPs and their biomedical applications are discussed and the present challenges and future perspectives of the biomedical applications of nanoMIPs are also highlighted.     

生物医用钙磷酸盐微晶玻璃

钙磷酸盐微晶玻璃因其具有生物活性、生物相容性 ,而广泛应用于牙科、骨科的替代及骨组织工程等领域。本文就钙磷酸盐微晶玻璃材料的制备工艺、组成性能、invitro vivo实验及医学应用作了较详细的评述。     

Shape Memory Materials for Biomedical Applications

Shape memory properties provide a very attractive insight into materials science, opening unexplored horizons and giving access to unconventional functions in every material class (metals, polymers, and ceramics). In this regard, the biomedical field, forever in search of materials that display unconventional properties able to satisfy the severe specifications required by their implantation, is now showing great interest in shape memory materials, whose mechanical properties make them extremely attractive for many biomedical applications. However, their biocompatibility, particularly for long‐term and permanent applications, has not yet been fully established and is therefore the object of controversy. On the other hand, shape memory polymers (SMPs) show promise, although thus far, their biomedical applications have been limited to the exploration. This paper will first review the most common biomedical applications of shape memory alloys and SMPs and address their critical biocompatibility concerns. Finally, some engineering implications of their use as biomaterials will be examined.     

Conjugated Polymer Actuators for Biomedical Applications

Conjugated polymers are electroactive and have found applications as artificial muscles. Actuators that have been developed over the last decade have now reached the early stages of commercialization, particularly for use in biomedical devices. This article reviews the motivation for using this class of actuator, the types of devices that have been fabricated, and some of the biomedical applications that are being developed. Recommendations are presented for future work on understanding the actuation mechanisms, on actuator design, and on the measurement of metrics.     

Microfluidic Generation of Nanomaterials for Biomedical Applications

As nanomaterials (NMs) possess attractive physicochemical properties that are strongly related to their specific sizes and morphologies, they are becoming one of the most desirable components in the fields of drug delivery, biosensing, bioimaging, and tissue engineering. By choosing an appropriate methodology that allows for accurate control over the reaction conditions, not only can NMs with high quality and rapid production rate be generated, but also designing composite and efficient products for therapy and diagnosis in nanomedicine can be realized. Recent evidence implies that microfluidic technology offers a promising platform for the synthesis of NMs by easy manipulation of fluids in microscale channels. In this Review, a comprehensive set of developments in the field of microfluidics for generating two main classes of NMs, including nanoparticles and nanofibers, and their various potentials in biomedical applications are summarized. Furthermore, the major challenges in this area and opinions on its future developments are proposed.     

Engineering Single-Atom Nanozymes for Catalytic Biomedical Applications

Nanomaterials with enzyme-mimicking properties, coined as nanozymes, are a promising alternative to natural enzymes owing to their remarkable advantages, such as high stability, easy preparation, and favorable catalytic performance. Recently, with the rapid development of nanotechnology and characterization techniques, single atom nanozymes (SAzymes) with atomically dispersed active sites, well-defined electronic and geometric structures, tunable coordination environment, and maximum metal atom utilization are developed and exploited. With superior catalytic performance and selectivity, SAzymes have made impressive progress in biomedical applications and are expected to bridge the gap between artificial nanozymes and natural enzymes. Herein, the recent advances in SAzyme preparation methods, catalytic mechanisms, and biomedical applications are systematically summarized. Their biomedical applications in cancer therapy, oxidative stress cytoprotection, antibacterial therapy, and biosensing are discussed in depth. Furthermore, to appreciate these advances, the main challenges, and prospects for the future development of SAzymes are also outlined and highlighted in this review.     

Sol-Gel Derived Hydroxylapatite Coatings for Biomedical Applications

This paper presents the preliminary findings of a novel coating technique for the deposition of hydroxylapatite coatings on ceramic substrates. Through the use of sol-gel methods crystalline coatings of hydroxylapatite on substrates of vycor glass, polycrystal line alumina and single crystal magnesia have been successfully produced. The production of sol-gel solutions, coatings and their analysis was examined by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Results thus far indicate that high quality hydroxylapatite coatings can be produced on ceramic substrates, with coatings deposited in this manner offering a number of benefits over other coating methods.     

有机室温磷光材料在生物医学中的应用

近年来,纯有机室温磷光(RTP)材料由于具有长的激发态寿命、大的Stokes位移、丰富的激发态性质等特点而备受研究者的广泛关注.相较于重金属配合物或无机磷光材料,有机磷光材料的原料来源广、成本低、合成条件温和,兼具质轻、柔性、可大面积制备等诸多优势,室温磷光材料在数据加密、传感、有机电致发光、生物成像等领域展现出良好的应用前景.有机磷光材料具有长寿命发光和三线态发射的特征,利用时间分辨技术能有效扣除生物组织自身的背景荧光干扰,极大地提高生物传感和成像的灵敏度与信噪比,并通过与三线态氧气的TTA过程,有望实现这类材料在光动力抗癌与抗菌等生物领域的应用.而且纯有机磷光材料不存在重金属元素的毒性问题.因此,纯有机磷光材料在生物成像、癌症治疗等生物领域实现很好的应用.本文总结了近年来有机室温磷光在生物应用中的研究进展,包括生物成像、生物传感、光动力抗癌、抗菌等.最后,提出该领域尚待解决的问题并展望未来前景.     

Biopolymer Microparticles Prepared by Microfluidics for Biomedical Applications

Biopolymers are macromolecules that are derived from natural sources and have attractive properties for a plethora of biomedical applications due to their biocompatibility, biodegradability, low antigenicity, and high bioactivity. Microfluidics has emerged as a powerful approach for fabricating polymeric microparticles (MPs) with designed structures and compositions through precise manipulation of multiphasic flows at the microscale. The synergistic combination of materials chemistry afforded by biopolymers and precision provided by microfluidic capabilities make it possible to design engineered biopolymer‐based MPs with well‐defined physicochemical properties that are capable of enabling an efficient delivery of therapeutics, 3D culture of cells, and sensing of biomolecules. Here, an overview of microfluidic approaches is provided for the design and fabrication of functional MPs from three classes of biopolymers including polysaccharides, proteins, and microbial polymers, and their advances for biomedical applications are highlighted. An outlook into the future research on microfluidically‐produced biopolymer MPs for biomedical applications is also provided.     

Metal–Organic Frameworks for Biomedical Applications

Metal–organic frameworks (MOFs) are an interesting and useful class of coordination polymers, constructed from metal ion/cluster nodes and functional organic ligands through coordination bonds, and have attracted extensive research interest during the past decades. Due to the unique features of diverse compositions, facile synthesis, easy surface functionalization, high surface areas, adjustable porosity, and tunable biocompatibility, MOFs have been widely used in hydrogen/methane storage, catalysis, biological imaging and sensing, drug delivery, desalination, gas separation, magnetic and electronic devices, nonlinear optics, water vapor capture, etc. Notably, with the rapid development of synthetic methods and surface functionalization strategies, smart MOF‐based nanocomposites with advanced bio‐related properties have been designed and fabricated to meet the growing demands of MOF materials for biomedical applications. This work outlines the synthesis and functionalization and the recent advances of MOFs in biomedical fields, including cargo (drugs, nucleic acids, proteins, and dyes) delivery for cancer therapy, bioimaging, antimicrobial, biosensing, and biocatalysis. The prospects and challenges in the field of MOF‐based biomedical materials are also discussed.     

A Novel Needle-Type SV-GMR Sensor for Biomedical Applications

Cancer is the most deadly disease in the world today. There is a variety of different treatment methods for cancer, including radiotherapy and chemotherapy with anticancer drugs that have been in use over a long period of time. Hyperthermia is one of the cancer treatment methods that utilizes the property that cancer cells are more sensitive to temperature than normal cells. The control of temperature is an important task in achieving success using this treatment method. This paper reports the development of a novel needle-type nanosensor based on the spin-valve giant magnetoresistive (SV-GMR) technique to measure the magnetic flux density inside the body via pricking the needle. The sensor has been fabricated. The modeling and experimental results of flux density measurement have been reported. From the information of flux density, the temperature rise can be estimated to permit the delivery of controlled heating to precisely defined locations in controlled hyperthermia cancer treatment. The actual experiment with human is under investigation     

Functional DNA Nanostructures for Photonic and Biomedical Applications

DNA nanostructures, especially DNA origami, receive close interest because of the programmable control over their shape and size, precise spatial addressability, easy and high‐yield preparation, mechanical flexibility, and biocompatibility. They have been used to organize a variety of nanoscale elements for specific functions, resulting in unprecedented improvements in the field of nanophotonics and nanomedical research. In this review, the discussion focuses on the employment of DNA nanostructures for the precise organization of noble metal nanoparticles to build interesting plasmonic nanoarchitectures, for the fabrication of visualized sensors and for targeted drug delivery. The effects offered by DNA nanostructures are highlighted in the areas of nanoantennas, collective plasmonic behaviors, single‐molecule analysis, and cancer‐cell targeting or killing. Finally, the challenges in the field of DNA nanotechnology for realistic application are discussed and insights for future directions are provided.