An Updated Review of Macro, Micro, and Nanostructured Hydrogels for Biomedical and Pharmaceutical Applications

Abstract

Hydrogels are materials with wide applications in several fields, including the biomedical and pharmaceutical industries. Their properties such as the capacity of absorbing great amounts of aqueous solutions without losing shape and mechanical properties, as well as loading drugs of different nature, including hydrophobic ones and biomolecules, give an idea of their versatility and promising demand. As they have been explored in a great number of studies for years, many routes of synthesis have been developed, especially for chemical/permanent hydrogels. In the same way, stimuli-responsive hydrogels, also known as intelligent materials, have been explored too, enhancing the regulation of properties such as targeting and drug release. By controlling the particle size, hydrogel on the micro- and nanoscale have been studied likewise and have increased, even more, the possibilities for applications of the so-called XXI century materials. In this paper, we aimed to produce an overview of the recent studies concerning methods of synthesis, biomedical, and pharmaceutical applications of macro-, micro, and nanogels.

The Double-Faced Electrostatic Behavior of PNIPAm Microgels

“…In the past decade, the synthesis of microgels with complex architectures received considerable attention. Among all the different known microgel morphologies, core/ shell [ 23 , 24 ] or multishell [ 25 , 26 ] structures represented the core of this line of research.…”

The Effects of Monomer, Crosslinking Agent, and Filler Concentrations on the Viscoelastic and Swelling Properties of Poly(methacrylic acid) Hydrogels: A Comparison

“…Hydrogels can be defined as hydrophilic polymeric networks formed from natural and/or synthetic polymers that are capable of absorbing and retaining a large amount of water or aqueous fluids without dissolving due to the crosslinked structure [ 1 ]. Over time, a wide variety of hydrogels have been obtained with applications in various fields such as medicine and pharmacy (drug delivery, tissue engineering, wound healing) [ 2 ], agriculture [ 3 ], electronic equipment industry [ 4 ], cosmetics industry [ 5 ], etc. The most important properties of hydrogels that must be taken into account in any application are the water content and the mechanical/viscoelastic properties, to which, depending on the use, others properties may be added, such as biocompatibility in the case of medical uses.…”

“…However, the mechanical properties of hydrogels are generally low, which is a major disadvantage in many situations. The simplest methods of improving the mechanical properties of common hydrogels are based on adjusting the crosslinking degree by either changing the concentration of the monomer introduced in the synthesis process or by altering the crosslinking agent–monomer ratio, or adding a reinforcing agent; the water absorption of the hydrogels is simultaneously affected in all these cases [ 2 , 6 , 7 ].…”

Self-Crosslinked Ellipsoidal Poly(Tannic Acid) Particles for Bio-Medical Applications

“…As microgels are versatile and have a broad range of applications covering food, cosmetic, energy, sensor, and medical fields, a facile and rapid synthesis without using many chemicals makes them more significant in these applications [ 38 , 39 , 40 ]. The tunable small sizes and functionality of microgels dignifies the value-added potentials in human-related in vivo applications [ 41 , 42 ].…”