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Bio–Nano Interface Technology for Biomedical Applications

Ana Luisa Gómez-Gómez1, Deyanira del Rosario Moguel-Concha1, José Eduardo Borges-Martínez1, Alma Leticia Martínez-Ayala2 and Gloria Dávila-Ortiz1*

1Departamento de Ingeniería Bioquímica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Av. Wilfrido Massieu S/N, Unidad Profesional Adolfo López Mateos, Zacatenco, Delegación Gustavo A. Madero, Ciudad de México, México

2Centro de Desarrollo de Productos Bióticos, Instituto Politécnico Nacional, Carretera Yautepec-Jojutla, Col. San Isidro, CEPROBI, Yautepec, Morelos, Mexico

Abstract

Nanoencapsulation protects biologically active compounds from deterioration due to system conditions such as oxidation, temperature, and pH changes, among other interactions that occur at the interface. Thus, biomedical applications of nanometric structures require the evaluation of a complex delivery system, in which the interactions that exist at the biomolecule–nanostructure interface, as well as their physicochemical properties, will determine the scope of the delivery system. A wide range of nanostructured materials exists. However, nanoencapsulation of bioactive compounds is a novelty. One advantage of nanoencapsulation is that nanostructures can be coated with biomolecules such as lipids, proteins, and polysaccharides, resulting in reduced surface energy and providing biological benefits to the organisms they interact with. It is essential to mention several challenges to implementing nanomaterials in biomedicine, among which toxicity and decreased efficacy stand out. These disadvantages occur mainly due to a lack of understanding of the interactions between nanomaterials and their biological environment. Currently, the use of nanomaterials is based primarily on the functionality of biomolecules. While nanomaterials are often designed to take advantage of the functionality of biomolecules, it is important to consider the potential impact of biomolecule–nanomaterial binding. Failure to account for such binding could lead to changes in the structure of the biomolecule, resulting in an altered or lost biological function of the compound. Additionally, binding could cause negative interactions between the bionanomaterial and the biological environment. The purpose of this chapter is to show the benefits of nanomaterials in conjunction with biomolecules in providing biological activity to help address various applications in the field of biomedicine, which will help to provide better and timely control of human health; as well as to identify the physicochemical properties of nanomaterials, which allow us to figure out what kind of interactions are involved at the bio–nano interface, due to their influence on the pharmacokinetic system stability associated with some parameters, such as the payload, release, and delivery efficiency. In addition, the effect of the physicochemical properties of nanomaterials and other factors that influence the structure, composition, and function of nanomaterial–bioactive compound complexes will be addressed, leading to a better understanding of the role of bioactive compound–nanomaterial interactions in controlling or predicting the biological fate of nanomaterials.

Keywords: Nanoencapsulation, bio–nano interface, bioactive compounds, fluidized bed

1.1 Physicochemical Properties of Nanoencapsulated Systems

Some physical and chemical aspects of nanoparticle carriers and encapsulated drug molecules have a substantial impact on the basic attributes of nano-sized drug products, such as drug circulation, drug release from site-specific dosage forms, and absorption into bodily membranes. Particle size has a significant impact on the stability of nanoemulsion complex, it has been reported that decreasing particle diameter increases the bioavailability of encapsulated compounds [1, 2]. Therefore, these are chief elements that correlate robustly concerning the stability of the encapsulated system. As a result, the particle characteristics are required to have an appropriate delivery system [3]. Smaller particle sizes provide a greater mass transfer area, leading to an improved drug diffusion rate. Conversely, the rate of drug dissipation within bigger particles is lower, as they offer a reduced mass transfer surface area. Smaller particles, on the other hand, tend to agglomerate when kept and moved [1]. The size of the particles can range from 10 nm (nanoemulsion) to 1 mm (hydrogel droplets). Colloidal reliable encapsulated particles are typically spherical. In contrast, distinct forms, among them cylinders, deformed spheres, or irregular shapes, have been noticed, influencing changes in the properties of particles and the interest compound delivery process [3]. The polydispersity of an enclosed system indirectly shows its aggregation status. Higher polydispersity implies the existence of aggregates, and this can cause destabilization and breakage in emulsion-based encapsulating systems. When the polydispersity of an encapsulating system is lower than 0.2, it is said to be monodisperse; nevertheless, polydispersity under the value of 0.5 is also regarded for pharmaceutical applications [3]. Droplet size is a relevant characteristic of emulsions because it promotes emulsion stability as droplet size and polydispersity decrease. The simplest and most common technique for measuring particle size and polydispersity is dynamic light scattering (DLS) [3]. It measures the intensity fluctuation of dispersed light. This fluctuation is the result of the interference of scattered light by individual particles just because of Brownian motion. The key advantages of DLS are its fast analytical speed, lack of calibration requirements, and excellent sensitivity to submicrometer particles [1]. Generally, the scattering angle is set to 90 degrees in most DLS techniques. For a monodisperse sample, the particle size should not change upon increasing the light scattering angle. Due to the extent of scattering at different angles being affected by particle size, the intensity-averaged mean particle size varies for polydisperse samples [3]. Now, the external charge of captured materials corresponds strongly with their dispersion stability. The zeta potential is frequently employed to analyze the surface charges of encapsulated materials, demonstrating the dominance of electrostatic forces indirectly [3]. In this connection, the use of the zeta potential makes it possible to visualize in encapsulations the influence of the charge of active molecules on the surface properties of the packing material. These enable the investigation of the stability of encapsulated materials besides the study of the electrostatic forces that occur between the active molecules and the encapsulating material. Colloidal stability is usually analyzed from the zeta potential of a nanoparticle. These measurements are performed with a zeta potential analyzer or zeta meter and allow prediction of the storage stability of various colloidal dispersions. To ensure stability and avoid particle aggregation, absolute zeta potential levels must be high, either positive or negative. The zeta potential measurements can be used to estimate the degree of surface hydrophobicity. The zeta (ζ) potential may provide additional details about the material enclosed in nanocapsules or coated on their surface [1]. A study on encapsulation used spray drying as a technique to obtain vitamin E-loaded nanocapsules using modified starches such as octenyl succinic anhydride (OSA), with two purposes as emulsifier and barrier material. The ζ-potential, size distributions, mean particle size, and polydispersity index (PDI) of the initial and reconstituted nanoemulsions were measured via DLS [1]. The mean particle diameters ranged from 208 to 235 nm. Although the mean hydrodynamic diameters were quite different, the PDI and ζ-potential values were similar. Furthermore, the reconstituted nanoemulsions retained their original trim monomodal distribution with a modest increase in mean particle sizes, according to the authors. It is noteworthy that the reconstituted emulsions kept their polydispersity values (PDI < 0.250) and particle sizes (< 250 nm) indicating that the spray-drying technique had no effect on the nanoemulsions’ properties [2]. As a result, the authors reported that OSA-modified starches with low molecular weight are efficacious in producing steady vitamin E nanocapsules for usage in pharmaceutical and food applications [2]. In another study, the authors evaluated the liberation of bioactive compounds with antioxidant and antihypertensive ability from packed extracts of Gulupa and Cholupa peel and seeds in an in vitro gastrointestinal model to simulate the process of digestion [4]. The encapsulates were constructed using wall material rice starch enzymatically modified. Characterization of the encapsulates revealed a range of electrical potential values between −6.34 and −6.66 mV. In addition, the DLS method determines the dispersion stability and disclosure PDI measurements from 1.33 to 1.51. The authors mentioned that the increment in the surface charge is due to the phenolic compounds on the particles. They observed that the wrapped extracts had an electronegative charge ζ-potential. As a result, the microcapsules showed high stability, so the encapsulates have an enormous amount of...