Nowadays, there are still numerous challenges for well-known biomedical applications, such as tissue engineering (TE), wound healing and controlled drug delivery, which must be faced and solved. Hydrogels have been proposed as excellent candidates for these applications, as they have promising properties for the mentioned applications, including biocompatibility, biodegradability, great absorption capacity and tunable mechanical properties. However, depending on the material or the manufacturing method, the resulting hydrogel may not be up to the specific task for which it is designed, thus there are different approaches proposed to enhance hydrogel performance for the requirements of the application in question. The main purpose of this review article was to summarize the most recent trends of hydrogel technology, going through the most used polymeric materials and the most popular hydrogel synthesis methods in recent years, including different strategies of enhancing hydrogels’ properties, such as cross-linking and the manufacture of composite hydrogels. In addition, the secondary objective of this review was to briefly discuss other novel applications of hydrogels that have been proposed in the past few years which have drawn a lot of attention.

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Novel Trends in Hydrogel Development for Biomedical Applications: A Review

High-strength hydrogels: Fabrication, reinforcement mechanisms, and applications

Highly flexible interconnected Li+ ion-sieve porous hydrogels with self-regulating nanonetwork structure for marine lithium recovery

While microgels and nanogels are most commonly used for the delivery of hydrophilic therapeutics, the water-swollen structure, size, deformability, colloidal stability, functionality, and physicochemical tunability of microgels can also offer benefits for addressing many of the barriers of conventional vehicles for the delivery of hydrophobic therapeutics. In this review, we describe approaches for designing microgels with the potential to load and subsequently deliver hydrophobic drugs by creating compartmentalized microgels (e.g., core-shell structures), introducing hydrophobic domains in microgels, leveraging host-guest interactions, and/or applying "smart" environmentally responsive materials with switchable hydrophobicity. In particular, the challenge of promoting hydrophobic drug loading without compromising the inherent advantages of microgels as delivery vehicles and ensuring practically relevant release kinetics from such structures is highlighted, with an eye toward the practical translation of such vehicles to the clinic.

Microgels and Nanogels for the Delivery of Poorly Water-Soluble Drugs.

While the intranasal administration of drugs to the brain has been gaining both research attention and regulatory success over the past several years, key fundamental and translational challenges remain to fully leveraging the promise of this drug delivery pathway for improving the treatment of various neurological and psychiatric illnesses. In response, this review highlights the current state of understanding of the nose-to-brain drug delivery pathway and how both biological and clinical barriers to drug transport using the pathway can been addressed, as illustrated by demonstrations of how currently approved intranasal sprays leverage these pathways to enable the design of successful therapies. Moving forward, aiming to better exploit the understanding of this fundamental pathway, we also outline the development of nanoparticle systems that show improvement in delivering approved drugs to the brain and how engineered nanoparticle formulations could aid in breakthroughs in terms of delivering emerging drugs and therapeutics while avoiding systemic adverse effects. 

https://link.springer.com/content/pdf/10.1007/s40263-022-00930-4.pdf

Using the Intranasal Route to Administer Drugs to Treat Neurological and Psychiatric Illnesses: Rationale, Successes, and Future Needs

A Review of Design and Fabrication Methods for Nanoparticle Network Hydrogels for Biomedical, Environmental, and Industrial Applications

Although nanoparticle-based chemotherapeutic strategies have gained in popularity, the efficacy of such therapies is still limited in part due to the different nanoparticle sizes needed to best accommodate different parts of the drug delivery pathway. Herein, we describe a nanogel-based nanoassembly based on the entrapment of ultrasmall starch nanoparticles (size 10-40 nm) within disulfide-crosslinked chondroitin sulfate-based nanogels (size 150-250 nm) to address this challenge. Upon exposure of the nanoassembly to the reductive tumor microenvironment, the chondroitin sulfate-based nanogel can degrade to release the doxorubicin-loaded starch nanoparticles in the tumor to facilitate improved intratumoral penetration. CT26 colon carcinoma spheroids could be efficiently penetrated by the nanoassembly (resulting in 1 order of magnitude higher DOX-derived fluorescence inside the spheroid relative to free DOX), while in vivo experiments showed that doxorubicin-loaded nanoassemblies reduced tumor sizes by 6× relative to saline controls and 2× relative to free DOX after 21 days. Together, these data suggest that nanogel-based nanoassemblies are a viable option for improving the efficacy and safety of nanoparticle-based drug delivery vehicles treating cancer.

Disulfide-Cross-Linked Nanogel-Based Nanoassemblies for Chemotherapeutic Drug Delivery.

Investigating the Kinetics and Structure of Network Formation in Ultraviolet-Photopolymerizable Starch Nanogel Network Hydrogels via Very Small-Angle Neutron Scattering and Small-Amplitude Oscillatory Shear Rheology

Matthew A. Campea

Papers

A Review of Design and Fabrication Methods for Nanoparticle Network Hydrogels for Biomedical, Environmental, and Industrial Applications

Disulfide-Cross-Linked Nanogel-Based Nanoassemblies for Chemotherapeutic Drug Delivery.

Investigating the Kinetics and Structure of Network Formation in Ultraviolet-Photopolymerizable Starch Nanogel Network Hydrogels via Very Small-Angle Neutron Scattering and Small-Amplitude Oscillatory Shear Rheology