Laser Transmission Spectroscopy Based on Tunable-Gain Dual-Channel Dual-Phase LIA for Biological Nanoparticles Characterization

Abstract

Size and absolute concentration of suspensions of nanoparticles are important information for the study and development of new materials and products in different industrial applications spanning from biotechnology and pharmaceutics to food preparation and conservation. Laser Transmission Spectroscopy (LTS) is the only methodology able to measure nanoparticle size and concentration by performing a single measurement. In this paper we report on a new variable gain calibration procedure for LTS-based instruments allowing to decrease of an order of magnitude the experimental indetermination of the particle size respect to the conventional LTS based on the double ratio technique. The variable gain calibration procedure makes use of a specifically designed tunable-gain, dual-channel, dual-phase Lock-In Amplifier (LIA) whose input voltage signals are those ones generated by two Si photodiodes that measure the laser beam intensities passing through the sample containing the nanoparticles and a reference optical path. The LTS variable gain calibration procedure has been validated by firstly using a suspension of NIST standard polystyrene nanoparticles even 36 hours after the calibration procedure was accomplished. The paper reports in detail the LIA implementation describing the design methodologies and the electronic circuits. As a case example of the characterization of biological nanostructures, we demonstrate that a single LTS measurement allowed to determine size density distribution of a population of extracellular vesicles extracted from orange juice (25 nm in size) with the presence of their aggregates having a size of 340 nm and a concentration smaller than 3 orders of magnitude.

Nanoscale Surface-Enhanced Raman Spectroscopy Investigation of a Polyphenol-Based Plasmonic Nanovector

“…Indeed, the CPP-CA@AgNPs seem to be enveloped by a layer of poorly scattering organic material, which does not appear in the CA@AgNP sample and can thus be ascribed to the aforementioned CPP corona [ 75 ]. This is confirmed by the light transmission spectroscopy (LTS) measurements and by the data analysis based on the Mie scattering theory, presented in Section E of the Supplementary Materials [ 35 ]. The estimates of the hydrodynamic diameters of the colloidal systems obtained by dynamic light scattering (DLS) corroborated the results obtained by LTS ( Supplementary Materials, Section E ).…”

“…The optical extinction spectrum of the samples was measured in a wide wavelength range, between 190 and 1300 nm, by employing a double ray spectrophotometer (v-590, Jasco) and quartz cuvettes with 1 mm path length. The data analysis procedure, based on Mie scattering, is discussed in reference [ 35 ].…”

“…The following Supplementary Materials can be downloaded at: ; Figure S1: caffeic acid Raman spectra in methanol and water solution, and in the powder form; Figures S2 and S3: theoretical SERS spectra for different caffeic acid - Ag atom three-dimensional configurations; Figure S4: theoretical SERS spectra for different catechol - Ag atom three-dimensional configurations; Figure S5: comparison between SERS and UV-Visible spectra of caffeic acid synthesized AgNPs with and without the capping agent; Figures S6–S8: particle size distribution for the two aforementioned systems obtained by SEM, LTS and DLS, respectively. Data are discussed by making use of references [ 35 , 76 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ].…”

Research progress of lock-in amplifiers

“…Gundogdu研究组 [63] 针对吸收光谱仪的应用场景, 结合峰值整形模拟前端电路设计, 提出了一种瞬态 锁相检测系统, 实验证明可将吸收光谱的灵敏度带 来数量级的提升; 德国明斯特大学的Brenker研究 组 [64] 介绍了一种将多通道锁相放大器用于膜电位 和离子荧光探针的各种组合, 可用于多路检测, 结 合光电倍增管进行弱荧光的锁相并行检测多细胞 信号, 以毫秒时间分辨率同时记录多个光电探针信 号, 实现细胞信号通路的原位动态监测; 借助锁相 放大器对噪声干扰的抑制, 靶标含量极低生物样品 的微弱发光信号也能被准确提取, 从而有望用于更 快更灵敏的核酸检测部件 [65] . 在环境监测应用中, 来自意大利罗马大学的Sarra等 [66] 报道将双通道 锁相放大器用于激光透射光谱检测, 来实现单分散 和多分散纳米颗粒的尺寸和浓度的快速测量, 结合 可变增益光谱校准方法能将颗粒度分析不确定度 降低1个数量级, 这给环境中生物团聚体检测提供 了先进的手段.…”

A 180 nm CMOS Integrated Optoelectronic Sensing System for Biomedical Applications

“…Optical sensor systems are also widely used in other fields of safety-healthcare applications, such as in wearable prosthetic systems [11][12][13][14], where a single or array of sensors are designed to increase the day-to-day patient life quality. Another important application of wearable optical sensors is the continuous environmental monitoring of workplaces where hazardous gases or nano-and/or micro-sized pollutants are employed with the aim of guaranteeing the health and safety of persons there operating [15][16][17].…”