Encapsulated fusion protein confers “sense and respond” activity to chitosan–alginate capsules to manipulate bacterial quorum sensing

Abstract

We demonstrate that "nanofactory"-loaded biopolymer capsules placed in the midst of a bacterial population can direct bacterial communication. Quorum sensing (QS) is a process by which bacteria communicate through small-molecules, such as autoinducer-2 (AI-2), leading to collective behaviors such as virulence and biofilm formation. In our approach, a "nanofactory" construct is created, which comprises an antibody complexed with a fusion protein that produces AI-2. These nanofactories are entrapped within capsules formed by electrostatic complexation of cationic (chitosan) and anionic (sodium alginate) biopolymers. The chitosan capsule shell is crosslinked by tripolyphosphate (TPP) to confer structural integrity. The capsule shell is impermeable to the encapsulated nanofactories, but freely permeable to small molecules. In turn, the capsules are able to take in substrates from the external medium via diffusion, and convert these via the nanofactories into AI-2, which then diffuses out. The exported AI-2 is shown to stimulate QS responses in vicinal Escherichia coli. Directing bacterial population behavior has potential applications in next-generation antimicrobial therapy and pathogen detection. We also envision such capsules to be akin to artificial "cells" that can participate in native biological signaling and communicate in real-time with the human microbiome. Through such interaction capabilities, these "cells" may sense the health of the microbiome, and direct its function in a desired, host-friendly manner.

Chitosan to Connect Biology to Electronics: Fabricating the Bio-Device Interface and Communicating Across This Interface

“…Table 2 illustrates further properties conferred by chitosan's amines. At low pH, the protonated amines make chitosan a polycation which promotes electrostatic interactions with (poly)anions (chitosan is often used for polyelectrolyte complexation) [33][34][35]. At high pH, the deprotonated amines have an unshared pair of electrons that are nucleophilic and can be readily modified by electrophiles (standard grafting/conjugation chemistries can be used to generate chitosan derivatives with diverse functional properties).…”

An investigation of the interactions between an E. coli bacterial quorum sensing biosensor and chitosan-based nanocapsules

“…In particular, in the recent years, an increasing number of studies have focused on exploring the impacts of nanomaterials on bacterial QS signaling. [30][31][32][33] These have included the study of nanomaterials loaded either with QS inhibitors [34], or with AIs, as well as polymeric materials obtained by molecular imprinting with high recognition capacity to sequester AHLs, and thus inhibit QS responses [35,36].…”

Directed assembly of a bacterial quorum

“…Recruiter capsules were developed largely as previously shown (Gupta et al, 2013). Cells (BL21 or BL21ΔluxS ) were grown to mid exponential phase and concentrated 30-fold by centrifugation and resuspension in LB broth.…”

“…Thus, CT104 are tracked by red fluorescence and when encountering a 'quorum'-producing level of AI-2, they fluoresce green. Non-fluorescing 'sentinel' cells were encapsulated within chitosan/alginate capsules (Gupta et al, 2013) in order to provide a centralized source of secreted AI-2 that diffuses into a quiescent buffer. We cocultured bacteria as depicted in Figure 4a; 'recruit' cells were placed in the top of a transwell apparatus and 'sentinel' cells were contained within capsules in the bottom compartment.…”