Self-adaptive non-covalent albumin-binding near-infrared probe conjugates enabling precise sentinel lymph node metastasis illumination and primary tumor imaging

Tumor sentinel lymph node(SLN)metastasis plays a vital role in tumor staging and therapeutic decision-making process.However,precise diagnosis of primary tumors and lymphatic metastases is still hindered by low imaging resolution and poor photostability of fluorescent probes.Herein,we report three novel IR820-fatty acid(FA)conjugates(IR-OA,IR-LA,and IR-PA)for precise lymphatic metastasis illumination and primary tumor diagnosis.The IR-FA conjugates are able to non-covalently bound to albumin in vivo,and the fluorescence quantum yield is significantly enhanced after incubation with bovine serum albumin(BSA)in vitro.Moreover,the BSA-IR-FA conjugates display large Stokes shift(>120 nm),dramatically improving in vivo imaging resolution.Among them,IR-PA demonstrates distinct advantage over IR-OA,IR-LA,and IR-maleimide(MAL)(fluorescent probe previously reported by our group)in terms of fluorescence quantum yield,photostability,and imaging resolution.As a result,IR-PA exhibits satisfactory imaging results with high fluorescence intensity and imaging resolution in sentinel lymph node metastasis illumination and primary tumor location.Our findings provide a self-adaptive albumin-binding near-infrared probe conjugate for accurate diagnosis of primary tumors and lymphatic metastases.

Facile synthesis of insulin fusion derivatives through sortase A ligation

Insulin derivatives such as insulin detemir and insulin degludec are U.S.Food and Drug Administration(FDA)-approved long-acting insulin currently used by millions of people with diabetes.These derivatives are modified in C-terminal B29 lysine to retain insulin bioactivity.New and efficient methods for facile synthesis of insulin derivatives may lead to new discovery of therapeutic insulin.Herein,we report a new method using sortase A(SrtA)-mediated ligation for the synthesis of insulin derivatives with high efficiency and functional group tolerance in the C-terminal B chain.This new insulin molecule(Ins-SA) with an SrtA-recognizing motif can be conjugated to diverse groups with N-terminal oligoglycines to generate new insulin derivatives.We further demonstrated that a new insulin derivative synthesized by this SrtA-mediated ligation shows strong cellular and in vivo bioactivity.This enzymatic method can therefore be used for future insulin design and development.