Over the years, the scientific importance of nanoparticles for biomedical applications has increased. The high stability and biocompatibility, together with the low toxicity of the nanoparticles developed lead to their use as targeted drug delivery systems, bioimaging systems, and biosensors. The wide range of nanoparticles size, from 10 nm to 1 μm, as well as their optical properties, allow them to be studied using microscopy and spectroscopy techniques. In order to be effectively used, the physicochemical properties of nanoparticle formulations need to be taken into account, namely, particle size, surface charge distribution, surface derivatization and/or loading capacity, and related interactions. These properties need to be optimized considering the final nanoparticle intended biodistribution and target. In this review, we cover light scattering based techniques, namely dynamic light scattering and zeta-potential, used for the physicochemical characterization of nanoparticles. Dynamic light scattering is used to measure nanoparticles size, but also to evaluate their stability over time in suspension, at different pH and temperature conditions. Zeta-potential is used to characterize nanoparticles surface charge, obtaining information about their stability and surface interaction with other molecules. In this review, we focus on nanoparticle characterization and application in infection, cancer and cardiovascular diseases.

Biosurfactant compounds have been studied in many applications, including biomedical, food, cosmetic, agriculture, and bioremediation areas, mainly due to their low toxicity, high biodegradability, and multifunctionality. Among biosurfactants, the lipoplexes of lipoaminoacids play a key role in medical and pharmaceutical fields. Lipoaminoacids (LAAs) are amino acid-based surfactants that are obtained from the condensation reaction of natural origin amino acids with fatty acids or fatty acid derivatives. LAA can be produced by biocatalysis as an alternative to chemical synthesis and thus become very attractive from both the biomedical and the environmental perspectives. Gemini LAAs, which are made of two hydrophobic chains and two amino acid head groups per molecule and linked by a spacer at the level of the amino acid residues, are promising candidates as both drug and gene delivery and protein disassembly agents. Gemini LAA usually show lower critical micelle concentration, interact more efficiently with proteins, and are better solubilising agents for hydrophobic drugs when compared to their monomeric counterparts due to their dimeric structure. A clinically relevant human gene therapy vector must overcome or avoid detect and silence foreign or misplaced DNA whilst delivering sustained levels of therapeutic gene product. Many non-viral DNA vectors trigger these defence mechanisms, being subsequently destroyed or rendered silent. The development of safe and persistently expressing DNA vectors is a crucial prerequisite for a successful clinical application, and it one of the main strategic tasks of non-viral gene therapy research.

Lipoaminoacids (LAA) are an important group of biosurfactants, formed by a polar hydrophilic part (amino acid) and a hydrophobic tail (lipid). The gemini LAA structures allow the formation of a supramolecular complex with bioactive molecules, like DNA, which provides them with good transfection efficiency. Since lipases are naturally involved in lipid and protein metabolism, they are an alternative to the chemical production of LAA, offering an eco-friendly biosynthetic process option. This work aimed to design the production of novel cystine derived gemini through a bioconversion system using immobilized lipases. Three lipases were used: porcine pancreatic lipase (PPL); lipase from Thermomyces lanuginosus (TLL); and lipase from Rizhomucor miehei (RML). PPL was immobilized in sol-gel lenses. L-cystine dihydrochloride and dodecylamine were used as substrates for the bioreaction. The production of LAA was evaluated by thin layer chromatography (TLC), and colorimetric reaction with eosin. The identification and quantification was carried out by High Performance Liquid Chromatographer-Mass Spectrometry (HPLC-MS/MS). The optimization of media design included co-solvent (methanol, dimethylsulfoxide), biphasic (n-hexane and 2-propanol) or solvent-free media, in order to improve the biocatalytic reaction rates and yields. Moreover, a new medium was tested where dodecylamine was melted and added to the cystine and to the biocatalyst, building a system of mainly undissolved substrates, leading to 5 mg/mL of LAA. Most of the volume turned into foam, which indicated the production of the biosurfactant. For the first time, the gemini derived cystine lipoaminoacid was produced, identified, and quantified in both co-solvent and solvent-free media, with the lipases PPL, RML, and TLL.

The authors wish to make the following erratum to this paper