Preface

Hydrogels are part of our day-to-day lives. They are components of our food and everyday objects. Most importantly, they are valuable intermediaries in the most innovative and unexpected attempts to cure, reduce the effects of diseases, and regenerate—in other words, to heal.

Hydrogels, as three-dimensional (3D) polymer networks, are able to retain a large amount of water in their swollen state and are the first biomaterials useful for therapy in humans. They are fascinating materials for developing innovative formulations and applications. Hydrogels have unique properties derived from their 3D viscoelastic networks, essentially permitting attachment and later diffusion of particles, molecules, or cells, as well as serving as 3D bioprinting materials for tissue engineering.

The applications of hydrogels cover a range of domains, from the food industry to pharmaceuticals (for example, in controlled drug or cell delivery) to modern medicine (for example, implants, diagnostics, wound dressings, bone regeneration, and soft contact lenses, to name only a few).

In the last few years, new methods have been developed for the preparation of hydrophilic polymers and hydrogels, which may be used in future biomedical and drug delivery applications. Such efforts include the synthesis of self-organized nanostructures based on triblock copolymers with applications in controlled drug delivery. These hydrogels could be used as carriers for drug delivery when combined with the techniques of drug imprinting and subsequent release.

Engineered protein hydrogels have many potential advantages. They are excellent biomaterials and biodegradables. Furthermore, they can encapsulate drugs and be used in an injectable form to replace surgery, to repair damaged cartilage, in regenerative medicine, or in tissue engineering. Also, they have potential use in gene therapy.

Significant advances have been made in the field of hydrogels as intelligent and functional materials. Their application in the biomedical field has been inherently hidden by the toxicity of cross-linking agents. Emerging knowledge in the field of chemistry, as well as the proper understanding of biological processes, has led to the rational use of hydrogels as versatile materials and as matrices helping in minimally invasive therapies. Today, hydrogels appear to have tremendously promising application potentials. However, a number of challenges remain for clinical translation.

This book provides an overview of multidisciplinary hydrogel research and the wider applicability of hydrogels.

> **Popa Lăcrămioara, PhD, Ghica Mihaela Violeta, PhD and Dinu-Pîrvu Cristina Elena, PhD** Faculty of Pharmacy, University of Medicine and Pharmacy Carol Davila, Bucharest, Romania

> > **1**

**Chapter 1**

**1. Introduction**

exemplify only a few.

specific environmental cues.

expanding.

Introductory Chapter: Hydrogels -

Hydrogels are part of our everyday life. They are components of our food [1–4], our everyday objects [5–7], but most importantly, they are valuable intermediaries in the most innovative and unexpected attempts to cure, to reduce the effects of the

Today, modern therapy gives a great value to tissue engineering and regenerative medicine (TERM) in various disease treatments [29]. In TERM, a great number of biomaterials are developed, and among them, hydrogels and scaffolds are occupying important places. The interest of the researchers in this subject is enormously

This book comes to give a small overview for multidisciplinary hydrogel research and widen applicability. That is the reason why the book opens with a board over-

The chapters of the book were majorly focused on the latest and emergent fields of interest: superabsorbent hydrogels, natural hydrogels based on chitosan, and a clinical grade hydrogel platform for drugs or cell/gene delivery, with potential-

An innovated class of recent generation of hydrogels includes superabsorbent hydrogels, and among them, cellulose-based superabsorbent hydrogels are important representative, due to a large availability of cellulose, it being environmental friendly, and its biocompatibility. It is largely presented in one of the chapters of the book. It is noted as smart materials, displaying stimuli-sensitive responsiveness to

Among the natural hydrogels, those based on chitosan and chitosan derivatives are described in another important chapter, with their biomedical application. Chitosan, as natural hydrophilic polymer, presents important deal of interest for hydrogel structures due to its biocompatibility and biodegradability. As biological

view of the hydrogel applications in drug delivery over last 10 years.

derived future organoid culture or bioprinting applications.

Hydrogels are known as the first biomaterials useful for therapy in humans [12], but they are still fascinating materials and subject for developing innovative formulations and applications [13–15]. They have unique properties derived from its three-dimensional (3D) viscoelastic network [16], essentially permitting attachment and later diffusion of particles, molecules, in controlled drug or cell/ gene delivery [17, 18], as well as serving as 3D bioprinting material [19, 20], in modern medicine, for tissue engineering [21, 22], as implants [23], for diagnostics [24], wound dressing [25], bone regeneration [26, 27], and soft contact lens [28], to

From First Natural Hydrocolloids

to Smart Biomaterials

*and Cristina Elena Dinu-Pîrvu*

*Lăcrămioara Popa, Mihaela Violeta Ghica* 

diseases, and to regenerate, in a single word—to heal [8–11].

## **Chapter 1**
