## 3 Functions of Dextran and Its Derivatives
### Dextran a Vehicle and Carrier for Drug Delivery
Reports have recommended that delivery vehicles with neutral surfaces of a hydrophilic nature, as in dextran molecules, are perfect for mucus permeation of drug molecules [35]. [PERSON] et al. investigated the issue of overcoming the diffusion barrier in mucus and the absorption barrier in epithelium by using self-assembled nanoparticles for the safer oral administration of insulin. Therefore, the above-mentioned properties make dextran an appropriate nanomaterial used to deliver micro concentrations of pharmaceutical compounds [36]. [PERSON] et al. studied the development of porous particles in a dry powder inhaler for enhanced delivery of rifampicin in the deep lung [37]. In this device, the acetalated dextran was applied as a sugar excipient. A suspension was prepared by mixing an ethanolic solution of rifampicin with an aqueous dextran solution, and then the powder was prepared by a spray-drying process of rifampicin suspension. Dextran-based nanoparticles have been explored as a vehicle for delivering therapeutic chemicals in the treatment of a few diseases. Although chemotherapy has been broadly used for the treatment of cancers, most drugs used as anticancer chemicals have insignificant water solubility and serious toxicity. The dextran nanocarriers have been suggested to enhance the bioavailability of pharmaceuticals. Carriers also lengthen the time for drugs' blood circulation and passively improve the accumulation of drugs in tumors by their higher permeation and retention [38; 39]. Many forms of nanoparticulate systems based on dextran for anticancer drug delivery have been investigated in the last few years [40; 41; 42; 43]. The current therapy for diabetes mellitus using insulin presents inconvenience and reduced conformity for patients' independence for physical intake; hence, nanocarriersbased on biopolymers have been developed for oral delivery of insulin [44; 45]. The dextran-based biodegradable and biocompatible nanoparticles have been formulated to solve this issue. [PERSON] et al. performed in vitro and in vivo evaluation of dextran-b-poly (lactide-co-glycolide) polymersome for oral administration of insulin [46]. A new dextran-based glucose/pH-responsive insulin delivery method was fabricated, and the insulin release in response to varying pH levels and glucose concentrations was further investigated in vitro by [PERSON] et al. [47]. In this design, an enzyme glucose oxidase was immobilized on acryloyl cross-linked dialdehyde dextran nanoparticles in a Schiff-base reaction. Nanocarrier using dextran is one of the favorable agents for traumatic spinal cord injury treatment. In a study by [PERSON] et al., methylprednisolone (MP) was integrated into ibuprofen-modified dextran nanoparticles for the delivery process; otherwise, it could cause serious side effects at high dosages [48]. The MP-loaded nanoparticles showed comparable therapeutic efficacy compared to free molecules of MP in in vivo experiments conducted on acute spinal cord injury model rats. [PERSON] et al. formulated acetalated dextran nanoparticles for the delivery of paclitaxel in the treatment of spinal cord injury [49]. An effective delivery approach with a profile of sustained release was developed to eliminate the biofilm matrix and destroy contained pathogenic microbes causing skin infections. The biocide hydrogel for antibiofilm treatment was prepared with dextran methacrylate copolymer as a delivery vehicle for the destruction of bacterial growth in biofilms [50]. [PERSON] and [PERSON] have reported that these dextran hydrogels could release the biocide chemical for a prolonged time period of 5 days. The retention of biocide chemicals helped in completely clearing the infection caused by _Escherichia coli_, _Staphylococcus aureus_, and methicillin-resistant _S. aureus_. Some dextran-based hydrogels presented advantages over other cationic hydrogels based on chitosan, with a higher strength to eradicate biofilm [51].