# Emerging Biomedical Applications of Carbon Dot and Polymer Composite Materials
## 3 Biomedical Applications of Carbon Dot/Polymer Composite Materials  
The low-dimensional nanoscale materials are increasingly studied in the healthcare area. Among them, metallic quantum dots (QDs) received considerable attention compared with carbon-based CDs nanoparticles. However, the CDs have unique physicochemical and photo-physical merits that can be better in different preclinical and clinical research. For instance, PEG-passivated CDs can provide biocompatibility and stealth character in an in vivo environment. Such attempts can be utilized in combination with different organic/inorganic agents for desired biomedical applications. It has been found in different studies that desired CDs/polymeric nanomaterials can be a potential candidate for drugand gene delivery in target areas such as a tumor (Figure 1b). It is one of few relatively less explored areas of CDs/polymeric nanomaterials in biomedical applications [58; 59]. The use of CD/polymer composites as a drug delivery system for chemotherapy drugs like doxorubicin, an anticancer drug, or biological molecules such as insulin-smart nanocarriers made by integrating insulin into CD/polymer hydrogels containing phenyl-boronic acid, which demonstrate a self-release pattern, are some of the most notable bio-medical applications [60; 61]. This makes it possible for the medicine to be delivered to the target tissue efficiently (Figure 1b). In addition, the developments for advanced drug delivery that can trigger externally are an attractive area of research. Such triggers can be used to control the dose and extend therapeutic outcomes. Recently, several triggerable nanomaterials have been studied that can be triggered such as light, ultrasound, and microwave. In this case, the CD/polymer can work as light trigger drug carriers. The drug release can be regulated through a photo-degradable bond, photo-induced hydrophobic/hydrophilic phase transition, or thermally by photothermal heat [23; 62; 63]. Additionally, PEG in this CD/polymer system can allow for long-term circulation before degradation and elimination from the body. The composite merit of the CD/polymer can be engineered in such a promising desired light-trigger drug delivery system [23; 64]. The nanoscale size and electronic conductivity features of carbon-based CDs exhibited photoluminescent (PL) properties. As a consequence of PL merits, the CDs can be studied in photothermal heat and photosensitive singlet oxygen (ROS, reactive oxygen species) generation for photothermal therapy (PTT) and photodynamic therapy (PDT)-based cancer therapy. The morphological and electronical properties of CD/polymer composites are also allowed for covalent and non-covalent conjugation with diagnostic and therapeutic drugs and genes. The prospect of CD/polymer NPs of such easy functionalization causes favorable diagnostic and therapeutic applications [59]. The growing nanotechnology and nanofabrication techniques address sensitive analytes detection up to nano-molar quantity at an affordable cost [58]. It is particularly essential since most existing detection and measurement processes involve sophisticated costly analytical instruments [65]. The sample preparation and conventional limit of detection (LOD) may not be suitable for all analyses. In this case, the optoelectronic, electronic, PL, and surface adsorption properties of the CD/polymeric NPs probe can be given superior strength in medical diagnoses, sensing, and treating different diseases [66]. Although organic fluorescence dyes are widely used in bioimaging, their stability and photo-bleaching are prime drawback features. The stable and biocompatible CD/polymer can be used as an alternative for live cell imaging and in vivo bioimaging materials [67; 68]. In addition, carbon dot/polymer composites are used in biosensing, bioimaging, and diagnostic applications to detect drugs and genetic materials (DNA or RNA) due to CDs' broad UV absorption spectrum and other physical, photothermal, mechanical stability, and chemical aspects [69].