M. Valizadeh Lakeh, YL Kong, MY Leong, C.Y. Looi
Hydrogels have long been utilized in biomedical implants and are now widely applied in the biomedical field as crosslinked polymers that closely mimic the properties of the body’s organs and tissues. Their unique characteristics make them excellent carriers for drugs, cells, and proteins. Over time, hydrogels have played a crucial role in advancing bioengineering, drug delivery, and tissue engineering by enhancing drug efficacy while reducing costs and side effects. Among their various applications, hydrogel-based nanocarriers have emerged as highly effective drug delivery systems. These carriers are designed with specialized strategies to incorporate stimuli-responsive properties, enabling them to react to external triggers such as light, ultrasound, pH, and temperature. Furthermore, their ability to selectively target specific cells or organs improves the precision of cytotoxic drug delivery, minimizing off-target effects. This review explores different hydrogel types, their mechanisms of action under specific stimuli, and the latest advancements and challenges in drug delivery research.