David Gintsburg

Mucoadhesive polymers are widely used in drug delivery to prolong residence time on mucus‐covered surfaces and enhance drug bioavailability, but conventional systems often suffer from broad molecular weight distributions and inconsistent performance. Here, three different amphiphilic co‐polymers based on bio‐sourced myrcene and PEG‐methacrylate are synthesized via Reversible Addition–Fragmentation Chain Transfer polymerization, yielding well‐defined polymers with narrow molar mass distributions. Structural analyses using ¹ H NMR spectroscopy and gel permeation chromatography confirm predominant 1,4‐addition and low dispersity. Energy‐filtered transmission electron microscopy and dynamic light scattering show self‐assembled nanostructures with mean diameters below 60 nm. In vivo toxicity evaluation in Galleria mellonella larvae demonstrates 100% survival after 48 h and prolonged polymer residence compared with PEG_4000. Mucoadhesion and mucopermeation assays reveal enhanced adhesion with intestinal mucus, with up to 50% retention after 3 h, a 6.6‐fold increase in mucus viscosity, and limited permeation (∼20%) into the mucus gel. Additionally, the polymers exhibit pronounced antioxidant activity (EC ₅₀ = 0.05% (m/V)) and antimicrobial activity against Escherichia coli ( E. coli ). Overall, high regioselectivity and controllable polymerization, combined with strong interactions with the intestinal mucosa, low toxicity, and biological effects, indicate that myrcene‐based co‐polymers are promising bio‐sourced candidates for use as active excipients in drug delivery.

Two β-cyclodextrin conjugates differing in their sulfur-bearing substituent, 1,2-dithiolane versus free thiols, were synthesized and evaluated as crosslinkers for polymeric mucin glycoproteins and thiolated polysaccharides, providing a comparison of ring-strain-driven thiol-disulfide exchange and oxidative disulfide formation. Per-thiolated β-cyclodextrin (β-CD-SH) was prepared via complete substitution of hydroxyl groups using phosphorous pentasulfide, while α-lipoic acid modified β-cyclodextrin (β-CD-LA) was obtained via esterification, introducing strained 1,2-dithiolane moieties as exchange-reactive disulfide units. Structural characterization by ¹H NMR and colorimetric assays confirmed successful functionalization of both derivatives. Safety profiles of the modified β‑cyclodextrins were evaluated regarding cytotoxicity, hemolysis, free radical interactions, and biodegradation. Rheological studies revealed stronger crosslinking (5.7-fold) of β-CD-LA with mucus glycoproteins compared to β-CD-SH, resulting in substantial viscosity enhancement and reduced diffusion through model mucus layers. Furthermore, β-CD-LA increased the viscosity of thiolated alginate by 22.1-fold and of thiolated xanthan by 77.3-fold, indicating rapid formation of disulfide-mediated polymer networks. These findings place the two β-cyclodextrin conjugates into distinct mechanistic categories: strain-activated dithiolane versus oxidation-driven thiol systems. This demonstrates that 1,2-dithiolane functionalization represents a superior strategy over free thiols for introducing dynamic covalent crosslinking capability into cyclodextrin-based scaffolds, supporting the use of dithiolane-bearing cyclodextrins as versatile multiarm crosslinkers for polymer network formation.

Hyaluronic acid (HA) is degraded by Staphylococcal hyaluronate lyase (Hysa) and mammalian hyaluronidase (Hyal). Thiolated HA (HAMS) is used as a targeted gateway for Staphylococcus aureus killing while enhancing the previous M23 endolysin–polyphosphate (M23‐PP NPs) enzyme‐responsive nanoparticle formulation. Synthesis of HAMS and characterization for nuclear magnetic resonance, solubility, thiol content, pKa, and degradation by Hysa and Hyal are presented. Nanoparticles prepared via ionotropic gelation between M23‐PP NPs and either HAMS or HA yield M23‐PP/HAMS or M23‐PP/HA NPs, respectively. Their characterization includes size, zeta potential, morphology, release profiles, safety, targeted release, and efficacy. HAMS with a thiol content of 250.18 ± 90.32 µmol g ⁻¹ , solubility of 50.99 ± 0.02 mg mL ⁻¹ , exhibits pKa values of 3.2, 4.2, and 8.8. This thiolated polymer irreversibly inhibits Hyal activity, without affecting Hysa. M23‐PP/HAMS NPs (265 ± 47 nm, −25 mV) maintain their integrity for seven days at 37 °C, and HAMS coating prevents nonspecific degradation by Hyal, as confirmed by release studies. In a co‐culture ‘race for the surface’ experiment with MC3T3 osteoblasts and S. aureus ATCC 25923, M23‐PP/HAMS NPs produce 8‐log bacterial killing while promoting in vitro wound healing. These findings are pivotal to the development of new enzyme‐responsive excipients switchable by S. aureus .

Stimuli-responsive nanomaterials show promise in eradicating Staphylococcus aureus biofilm from implants. Peptidoglycan hydrolases (PGHs) are cationic antimicrobials that can be bioengineered to improve the targeting of persisters and drug-resistant bacteria. However, these molecules can be degraded before reaching the target and/or present limited efficacy against biofilm. Therefore, there is an urgent need to improve their potency. Herein, PGH–polyphosphate nanoparticles (PGH–PP NPs) are formed by ionotropic gelation between cationic PGHs and anionic polyphosphate, with the aim of protecting PHGs and delivering them at the target site triggered by alkaline phosphatase (AP) from S. aureus biofilm. Optimized conditions for obtaining M23–PP NPs and GH15–PP NPs are presented. Size, zeta potential, and transmission electron microscopy imaging confirm the nanoscale size. The system demonstrates outstanding performance, as evidenced by a dramatic reduction in PGHs’ minimum inhibitory concentration and minimum bactericidal concentration, together with protection against proteolytic effects, storage stability, and cytotoxicity towards the Caco-2 and HeLa cell lines. Time-kill experiments show the great potential of these negatively charged delivery systems in overcoming the staphylococcal biofilm barrier. Efficacy under conditions inhibiting AP proves the enzyme-triggered delivery of PGHs. The enzyme-responsive PGH–PP NPs significantly enhance the effectiveness of PGHs against bacteria residing in biofilm, offering a promising strategy for eradicating S. aureus biofilm.