Small But Smart Delivery

People diagnosed with conditions tend to look at the bigger picture; they want their whole body back in healthy condition. However, sometimes it is necessary to zoom in on distinct parts of the picture. Focusing on the specific body part that needs treatment is essential. An example is when a patient requires the regeneration of tissues with the formation of neovessels. Neovessels help build up the tissues in our body by forming new blood vessels and “play a critical role in homeostasis, regeneration, and pathogenesis of tissues and organs, and their spatial organization is a major factor in influencing vascular function” [1]. A new method is being used to treat patients with few options on such a small scale: Hydrogels.

Hydrogels are used more for efficient drug delivery as they can act as carriers to various sites within the body. With a crosslinked network of hydrophilic polymers, hydrogels can swell up and retain a large volume of water while maintaining their structure [2]. Hydrogels are generally classified based on their composition and derivation. For example, hydrogels can be engineered with poly(ethylene oxide) (PEO), poly(hydroxyethyl methacrylate) (PHEMA), and poly(vinyl alcohol) (PVA). These are different types of neutral polymers that crosslink to form hydrogels. PEO and PEG polymers are highly soluble in water; thus the crosslinking mechanisms allow them to retain the swelling of water and act as an energy storage device. PVA is a common synthetic organic polymer that helps the structure maintain its elasticity and stability and is frequently used in pharmaceuticals, medicine, water purification, and energy storage [3].

The hydrophilic characteristics allow hydrogels to maintain their structure in the bloodstream. Therefore, instead of operating on the patient and attempting to fix the entire blood vessel, the hydrogels can be placed inside the body to implant the drug internally. For instance, Vascular Endothelial Growth Factor (VEGF), a growth factor for vascular endothelial cells, can be engineered in the center of the hydrogel to be released into the blood vessels for the development of neovessels. Thus, the hydrogel can be implemented into a person’s blood vessel and release VEGF, allowing new blood vessels to form to regenerate tissues [1]. In addition, health professionals can take advantage of how the drug can be kept between the cross-linkers by swelling and how the drug is slowly released in the body.

Although hydrogels have a high swelling factor that allows drugs and water to sustain their structure, they lack mechanical strength [4]. This causes the hydrogel to burst when the drugs are encapsulated within the hydrogel initially. Moreover, the cross-linking mechanisms do not have a method of sustained release for the drug [5]. In context, the VEGF engineered into the hydrogel would be released shortly after the hydrogel is implemented into the blood vessels which would not facilitate the natural regeneration of tissue.

The limitations of hydrogels demonstrate how extensive research allows the use of hydrogels in a healthcare setting.. For instance, the crosslinking mechanisms of polymers can be engineered such that the polymers self-assemble to naturally open up within the gel to allow drugs to be released over a long time period [1]. With this mechanism, hydrogels can be used beyond the regeneration of tissues and neovessels. For instance, it can be used to treat diabetic wounds in type 2 diabetes patients and cancer, both very prevalent diseases with few treatment options. By using inflammatory response drugs in the crosslinked hydrophilic polymer, patients with type 2 diabetes can speed up the process of angiogenesis during wound healing [6]. The flexible implications of hydrogels gives hope to thousands of patients without treatment options in hand.

References

1. Jeong, J. H., Chan, V., Cha, C., Zorlutuna, P., Dyck, C., Hsia, K. J., Bashir, R., & Kong, H. (2011). “Living” Microvascular Stamp for Patterning of Functional Neovessels; Orchestrated Control of Matrix Property and Geometry. Advanced Materials, 24(1), 58–63. https://doi.org/10.1002/adma.201103207

2. Bahram, M., Mohseni, N., & Moghtader, M. (2016). An Introduction to Hydrogels and Some Recent Applications. In (Ed.), Emerging Concepts in Analysis and Applications of Hydrogels. IntechOpen. https://doi.org/10.5772/64301

3. Youhong Guo, Jiwoong Bae, Zhiwei Fang, Panpan Li, Fei Zhao, and Guihua Yu (2020). Hydrogels and Hydrogel-Derived Materials for Energy and Water Sustainability. Chemical Reviews 2020 120 (15). DOI: 10.1021/acs.chemrev.0c00345

4. Billiet, T., Vandenhaute, M., Schelfhout, J., Van Vlierberghe, S., & Dubruel, P. (2012). A review of trends and limitations in hydrogel-rapid prototyping for tissue engineering. Biomaterials, 33(26), 6020–6041. https://doi.org/10.1016/j.biomaterials.2012.04.050

5. Billiet, T., Vandenhaute, M., Schelfhout, J., Van Vlierberghe, S., & Dubruel, P. (2012). A review of trends and limitations in hydrogel-rapid prototyping for tissue engineering. Biomaterials, 33(26), 6020–6041. https://doi.org/10.1016/j.biomaterials.2012.04.050

6. ‌Hao, M., Ding, C., Sun, S., Peng, X., & Liu, W. (2022). Chitosan/Sodium Alginate/Velvet Antler Blood Peptides Hydrogel Promotes Diabetic Wound Healing via Regulating Angiogenesis, Inflammatory Response and Skin Flora. Journal of Inflammation Research, Volume 15, 4921–4938. https://doi.org/10.2147/jir.s376692