Nanomaterials are becoming important materials in several fields and industries thanks to their very reduced size and shape-related features. Scientists think that nanoparticles and nanostructured materials originated during the Big Bang process from meteorites leading to the formation of the universe and Earth. Since 1990, the term nanotechnology became very popular due to advances in imaging technologies that paved the way to specific industrial applications. Currently, nanoparticles and nanostructured materials are synthesized on a large scale and are indispensable for many industries. This fact fosters and supports research in biochemistry, biophysics, and biochemical engineering applications. Recently, nanotechnology has been combined with other sciences to fabricate new forms of nanomaterials that could be used, for instance, for diagnostic tools, drug delivery systems, energy generation/storage, environmental remediation as well as agriculture and food processing. In contrast with traditional materials, specific features can be integrated into nanoparticles, nanostructures, and nanosystems by simply modifying their scale, shape, and composition. This article first summarizes the history of nanomaterials and nanotechnology. Followed by the progress that led to improved synthesis processes to produce different nanoparticles and nanostructures characterized by specific features. The content finally presents various origins and sources of nanomaterials, synthesis strategies, their toxicity, risks, regulations, and self-aggregation.

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Review on Natural, Incidental, Bioinspired, and Engineered Nanomaterials: History, Definitions, Classifications, Synthesis, Properties, Market, Toxicities, Risks, and Regulations

Microfluidic nanomaterials: From synthesis to biomedical applications.

Metallic nanoparticles have found various biomedical applications due to their intrinsic physicochemical properties. As the size decreases, the high surface area of particles gives rise to distinctive features, which are entirely different from that of a macro-sized structure. Several methods are involved in synthesizing metallic nanoparticles, and in general, it can be categorized into either bottom-up or top-down approaches. The top-down method consists of cutting down the bulk materials into nano-sized particles through physical, chemical, or mechanical treatments, whereas, in a bottom-up approach, nanoparticles are formed by joining individual atoms or molecules. The top-down approach produces metallic nanoparticles in naked form, which can further agglomerate and hence not suitable for biomedical applications. The bottom-up approach involves solid-state, liquid state, gas phase, biological, microfluidic-technology based, and other methods. Chemical reduction in the bottom-up approach is the most common method of metallic nanoparticle synthesis, which is flexible, simpler, inexpensive, and produces particles in homogenous form. Recently biological method of nanoparticle synthesis has become popular due to its toxic-free nature, inexpensiveness, sustainability, and eco-friendly. In this chapter, we describe the top-down and bottom-up approach and current trends in the synthesis of metallic nanoparticles for biomedical purposes. Further, it explains how the parameters can be tuned to get metallic nanoparticles with the desired shape, size, morphology, composition and crystallinity.

Metallic nanoparticles for biomedical applications

Nanotechnology offers a significant advantage in science, engineering, medicine, medical surgery, foods, packing, clothes, robotics, and computing from the beginning of the twenty-first century. As the potential scientific discovery always contains some good and bad effects on human civilization and the environment, nanotechnology is not an exception. The major drawbacks include economic disruption along with imposing threats to security, privacy, health, and environment. The introduction of the chapter discusses the historical background of nanotechnology. Later it also discusses the advancement of nanotechnology to date with its benefits. Major drawbacks of nanotechnology arise in human health due to the enormous involvement in medicine, food, agriculture, etc. This chapter also deals with environmental nano pollution and its effect on society, highlighting the social-economic disruption due to the rapid use of nanotechnology. Nano pollution affects not only human beings but also other living beings like microorganisms, animals and plants, which are briefly reviewed. This chapter also demonstrates the safety and security of nanotechnological developments, current policy and regulation status, challenges, and future trends. Finally, it is concluded, while nanotechnology offers more efficient power sources, faster and modern computers and technologies, life-saving medical treatments, but due to some negative impacts, it bounds us to think twice before any further advanced technological applications.

Nanomaterials: An Introduction

This work presents the synthesis of anisotropic gold nanocrystals (Au NCs) using a segmented flow-based microfluidic device, and intracellular delivery using the synthesized particles. The device consists of T and Y shape junctions, cross channel, and winding geometries, where reagents mix. Reagents meet at the initial Y-junction and the T-shape junction generates droplets. Synthesized Au NCs are characterized and are found to possess multiple plasmonic peaks as per their size, shape and anisotropic nature. These plasmonic peaks can be tuned to the near-infrared region, which is advantageous in different biomedical applications. With the synthesized Au NCs as a mediator, propidium iodide dye is successfully delivered into the cellular cytoplasm of HeLa cells by using nanosecond pulse laser. The results demonstrated that Au NCs synthesized using a segmented flow-based microfluidic device can be used for the intracellular delivery of different exogenous molecules. The best results are achieved as 96% delivery efficiency and 98% cell viability. Thus, our platform potentially applicable to anisotropic Au NCs synthesis as well as cellular therapy and diagnostic purpose.

Intracellular Delivery using Anisotropic Gold Nanocrystals Synthesized by Microfluidic Device

Nanotechnology has shown promise in biomedical applications for diagnosis and treatment purposes. This chapter describes the synthesis of different metal nanoparticles using microfluidic devices and their potential biomedical applications, such as sensing, imaging, and therapeutics and diagnostics. Multiphase microfluidics is complex compared to single-phase microfluidics. Its design and function include interaction among various physiochemical phenomena, such as chemical reactions, heat and mass transport, and the hydrodynamics of fluid and the surface phenomenon. Continuous- (laminar) and segmented-flow types of microfluidic processes have been used to synthesize metallic nanoparticles, with their unique physical and chemical characteristics and controlled nano-structure. Biosensing is an important tool for early detection and sensing of medical parameters for healthcare applications. Optical properties of metallic nanoparticles provide many opportunities in biosensing. The chapter also elaborates the future challenges of nanoparticle preparation using microfluidic devices and their applications, advantages, and limitations.

Ashwin Kumar Narasimahan

Papers

Microfluidics-Based Metallic Nanoparticle Synthesis and Applications