Redox-Responsive Hyaluronic Acid-Tacrolimus Conjugate: Synthesis, Characterization, and In Vitro Immunosuppressive Activity

Sulfated hyaluronic acid gel for the treatment of rheumatoid arthritis in rats

Rheumatoid arthritis (RA) is a chronic autoimmune disease. NSAIDS, cyclophosphamide and glucocorticoid were commonly used to treat RA in clinical application, which long-term administration of these drugs caused serious adverse reactions. Therefore, sulfated hyaluronic acid (sHA) gel (SG) was prepared to firstly treat the RA and avoid the problem of toxic side effect caused by long-term application. In vitro evaluation showed that sHA inhibited the level of reactive oxygen species and TNF-α, IL-1β, and IL-6, and decreased the ratio of macrophage M1/M2 type, which exerted better anti-inflammatory capacity. In vivo studies showed that the injection of SG into the joint cavity of collagen-induced rheumatoid arthritis (CIA) rats could effectively treat joint swelling and reduce the level of inflammatory factors in the serum. Immunofluorescence showed that SG exerted its anti-inflammatory activity by decreasing the ratio of M1/M2 type macrophages in synovial tissue. Cartilage tissue sections showed that SG reduced bone erosion and elevated chondrocyte expression. These results confirmed that sHA is expected to be developed as a drug to treat or relieve RA, which could effectively regulate the level of macrophages in rat RA, alleviate the physiological state of inflammatory over-excitation, and improve its anti-inflammatory and antioxidant capacity.

Recent advances in pH/enzyme-responsive polysaccharide-small-molecule drug conjugates as nanotherapeutics

Now-a-days, the polysaccharides are extensively employed for the delivery of small-molecule drugs ascribed to their excellent biocompatibility, biodegradability and modifiability. An array of drug molecules is often chemically conjugated with different polysaccharides to augment their bio-performances. As compared to their therapeutic precursors, these conjugates could typically demonstrate an improved intrinsic solubility, stability, bioavailability and pharmacokinetic profiles of the drugs. In current years, various stimuli-responsive particularly pH and enzyme-sensitive linkers or pendants are also exploited to integrate the drug molecules into the polysaccharide backbone. The resulting conjugates could experience a rapid molecular conformational change upon exposure to the microenvironmental pH and enzyme changes of the diseased states, triggering the release of the bioactive cargos at the targeted sites and eventually minimize the systemic side effects. Herein, the recent advances in pH and enzyme -responsive polysaccharide-drug conjugates and their therapeutic benefits are systematically reviewed, following a brief description on the conjugation chemistry of the polysaccharides and drug molecules. The challenges and future perspectives of these conjugates are also precisely discussed.