Polymer nanoparticles: Preparation techniques and size-control parameters

Nanoscience is an emerging area of science that has the potential to generate radical new products and processes. Concepts in nanoscience provide a sound framework for developing an understanding of the interactions and assembly behaviour of food components into microstructure, which influence food structure, rheology and functional properties at the macroscopic scale. Advances in processes for producing nanostructured materials coupled with appropriate formulation strategies have made possible the production and stabilisation of nanoparticles that have potential applications in the food and related industries.

Nanoscale materials development - a food industry perspective

The interest in the preparation and application of nanometer size materials is increasing since they can exhibit properties of great industrial interest. Several techniques have been proposed to produce nanomaterials using supercritical fluids. These processes, taking advantage of the specific properties of supercritical fluids, are generally flexible, more simplified and with a reduced enviromental impact. The result is that nanomaterials with potentially better performances have been obtained. We propose a critical review of the supercritical based techniques applied to the production of nanoparticles, nanofibers, nanowires, nanotubes, nanofilms and nanostructured materials. The most relevant characteristics of each process and the kind of nanomaterial that can be produced are highlighted.

Nanomaterials and supercritical fluids

Supercritical fluids (SCFs) have been used to deposit thin metal films onto a wide range of surfaces and incorporate metallic particles into different inorganic and organic substrates for microelectronic, optical and catalytic applications. The technique involves the dissolution of a metallic precursor in a SCF and the exposure of a substrate to the solution. After incorporation of the precursor with the substrate, the metallic precursor is reduced to its metal form by a wide variety of methods resulting in films or particles. The reduction methods employed are chemical reduction in the SCF with a reducing agent, such as hydrogen and alcohols, thermal reduction in the SCF and thermal decomposition in an inert atmosphere or chemical conversion with hydrogen or air. Both highly dispersed and uniformly distributed metal crystallites (

Preparation of supported metallic nanoparticles using supercritical fluids: A review

The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy has emerged as one of the most advanced, with the capability to tackle disorders from the modern era. However, there are several barriers associated with the delivery of genes in the living system that need to be mitigated by polymer engineering. One of the most crucial challenges is the effectiveness of the delivery vehicle or vector. In last few decades, non-viral delivery systems have gained attention because of their low toxicity, potential for targeted delivery, long-term stability, lack of immunogenicity, and relatively low production cost. In 1987, Felgner et al. used the cationic lipid based non-viral gene delivery system for the very first time. This breakthrough opened the opportunity for other non-viral vectors, such as polymers. Cationic polymers have emerged as promising candidates for non-viral gene delivery systems because of their facile synthesis and flexible properties. These polymers can be conjugated with genetic material via electrostatic attraction at physiological pH, thereby facilitating gene delivery. Many factors influence the gene transfection efficiency of cationic polymers, including their structure, molecular weight, and surface charge. Outstanding representatives of polymers that have emerged over the last decade to be used in gene therapy are synthetic polymers such as poly(l-lysine), poly(l-ornithine), linear and branched polyethyleneimine, diethylaminoethyl-dextran, poly(amidoamine) dendrimers, and poly(dimethylaminoethyl methacrylate). Natural polymers, such as chitosan, dextran, gelatin, pullulan, and synthetic analogs, with sophisticated features like guanidinylated bio-reducible polymers were also explored. This review outlines the introduction of polymers in medicine, discusses the methods of polymer synthesis, addressing top down and bottom up techniques. Evaluation of functionalization strategies for therapeutic and formulation stability are also highlighted. The overview of the properties, challenges, and functionalization approaches and, finally, the applications of the polymeric delivery systems in gene therapy marks this review as a unique one-stop summary of developments in this field.

https://www.mdpi.com/2073-4360/11/4/745/pdf

Polymeric Nanoparticles in Gene Therapy: New Avenues of Design and Optimization for Delivery Applications.

Supercritical-fluid processing technique for nanoscale polymer particles.

Nanocrystalline CdS particles directly conjugated with bovine serum albumin (BSA) protein were prepared by applying the supercritical fluid processing technique, rapid expansion of a supercritical solution into a liquid solvent. The direct conjugation takes advantage of the unique features of the process for nanoparticle formation. The BSA-conjugated CdS nanoparticles in stable aqueous suspension or in the solid state were characterized by using microscopy, X-ray diffraction, and optical spectroscopy methods. The results show that well-dispersed CdS nanoparticles are coated with BSA in a core-shell-like arrangement and that the protein species associated with the nanoparticles remain functional according to the modified Lowry assay. These BSA-conjugated CdS nanoparticles are also strongly luminescent, with the luminescence spectrum contributed to primarily by the exciton emission.

Razvan Hurezeanu

Papers

Supercritical-fluid processing technique for nanoscale polymer particles.

Direct conjugation of semiconductor nanoparticles with proteins.