Fast functionalization of ultrasound microbubbles using strain promoted click chemistry

Abstract

Functionalization of microbubbles (MBs) is a difficult issue due to their unstable nature. Here we report a fast and versatile method using a strain promoted alkyne-azide cycloaddition (SPAAC) click reaction for microbubble functionalization. An azadibenzocyclooctyne (DBCO) group was first introduced onto the MB surface and then an azide group into the desired ligand. Without any initiators or catalysts, essential click ligation occurred within 1 min and a majority of the reaction completed in 5 min at 37 °C. This fast ligation shortens the microbubble reaction time and preserves essential amounts of microbubbles for further in situ imaging and delivery of therapeutics.

Ultrasound‐Triggered Delivery of Iproplatin from Microbubble‐Conjugated Liposomes

“…The click reaction between L(Pt)‐N 3 liposomes and DBCO (18 : 1 dibenzocyclooctyl PE) lipid was carried out immediately after liposome fabrication and purification, by addition of the liposome solution to a mixture of DPPC, DSPE−mPEG(2000) and DSPE−PEG(2000)‐DBCO (82 : 9 : 9 molar ratio) which had been rehydrated with an 8 : 1 : 1 mixture of phosphate‐buffered saline (PBS), propylene glycol and glycerine (see Supporting Information). The time to completion for the click reaction was anticipated to depend on the components; although the reaction of DBCO‐functionalised MB with azido‐containing compounds has been reported to complete within 5 min, [60] the reaction between a DBCO‐containing compound and an azido‐functionalised cellular surface component has been reported to continue to progress over a 30 min period. [61] We allowed the click reaction to proceed overnight before microbubble manufacture.…”

“…Loading method c(drug) [mg mL À 1 ] c(drug) [mm] Pt : P ratio c(lipid) [mg mL À 1 ] Drug/lipid ratio [mg mg tion). The time to completion for the click reaction was anticipated to depend on the components; although the reaction of DBCO-functionalised MB with azido-containing compounds has been reported to complete within 5 min, [60] the reaction between a DBCO-containing compound and an azidofunctionalised cellular surface component has been reported to continue to progress over a 30 min period. [61] We allowed the click reaction to proceed overnight before microbubble manufacture.…”

Microbubbles Stabilized by Protein Shell: From Pioneering Ultrasound Contrast Agents to Advanced Theranostic Systems

“…An important and insufficiently disclosed area at the moment is synthetic biopolymers based on oligopeptides for MB fabrication. At the moment, the main natural proteins used for MB fabrication are (Figure 2): bovine and human serum albumins (BSA and HSA) [43,44,[66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84], hemoglobin [85], lysozyme [86][87][88][89][90][91][92][93], hydrophobin [94], and oleosin [95,96].…”

Improving accessibility of EPR-insensitive tumor phenotypes using EPR-adaptive strategies: Designing a new perspective in nanomedicine delivery

“…It encompasses both encapsulation of nanoparticles within the microbubble and chemical tethering of agents to the microbubble shell (Figure 2E) 80. While encapsulation is largely limited to hydrophobic loads that can sequester within the microbubble shell or sit at the shell-air interface 81,82, tethering allows for attachment of almost any agent using reliable linking strategies such as biotin-streptavidin binding 83,84,85,86 or click chemistry 87,88 and versatile carriers such as liposomes 85,89. Tinkov et al were one of the first groups to fabricate microbubbles with liposomal doxorubicin and showed a 12-fold increase in drug accumulation in DSL6A murine pancreatic xenografts compared to non-irradiated tumors in a bilateral tumor model (Figure 2F) 90.…”