Polyphosphoester-stabilized cubosomes encapsulating a Ru(II) complex for the photodynamic treatment of lung adenocarcinoma

The clinical translation of photosensitizers based on ruthenium(II) polypyridyl complexes (RPCs) in photodynamic therapy of cancer faces several challenges. To address these limitations, we conducted an investigation to assess the potential of a cubosome formulation stabilized in water against coalescence utilizing a polyphosphoester analog of Pluronic F127 as a stabilizer and loaded with newly synthesized RPC-based photosensitizer [Ru(dppn)2(bpy-morph)](PF6)2 (bpy-morph = 2,2'-bipyridine-4,4'-diylbis(morpholinomethanone)), PS-Ru. The photophysical characterization of PS-Ru revealed its robust capacity to induce the formation of singlet oxygen (1O2). Furthermore, the physicochemical analysis of the PS-Ru-loaded cubosomes dispersion demonstrated that the encapsulation of the photosensitizer within the nanoparticles did not disrupt the three-dimensional arrangement of the lipid bilayer. The biological tests showed that PS-Ru-loaded cubosomes exhibited significant phototoxic activity when exposed to the light source, in stark contrast to empty cubosomes and to the same formulation without irradiation. This promising outcome suggests the potential of the formulation in overcoming the drawbacks associated with the clinical use of RPCs in photodynamic therapy for anticancer treatments.

Real-time 31P NMR reveals different gradient strengths in polyphosphoester copolymers as potential MRI-traceable nanomaterials

Polyphosphoesters (PPEs) are used in tissue engineering and drug delivery, as polyelectrolytes, and flame-retardants. Mostly polyphosphates have been investigated but copolymers involving different PPE subclasses have been rarely explored and the reactivity ratios of different cyclic phospholanes have not been reported. We synthesized binary and ternary PPE copolymers using cyclic comonomers, including side-chain phosphonates, phosphates, thiophosphate, and in-chain phosphonates, through organocatalyzed ring-opening copolymerization. Reactivity ratios were determined for all cases, including ternary PPE copolymers, using different nonterminal models. By combining different comonomers and organocatalysts, we created gradient copolymers with adjustable amphiphilicity and microstructure. Reactivity ratios ranging from 0.02 to 44 were observed for different comonomer sets. Statistical ring-opening copolymerization enabled the synthesis of amphiphilic gradient copolymers in a one-pot procedure, exhibiting tunable interfacial and magnetic resonance imaging (MRI) properties. These copolymers self-assembled in aqueous solutions, 31 P MRI imaging confirmed their potential as MRI-traceable nanostructures. This systematic study expands the possibilities of PPE-copolymers for drug delivery and theranostics.

Biodegradable polyphosphoester micelles act as both background-free 31P magnetic resonance imaging agents and drug nanocarriers

In vivo monitoring of polymers is crucial for drug delivery and tissue regeneration. Magnetic resonance imaging (MRI) is a whole-body imaging technique, and heteronuclear MRI allows quantitative imaging. However, MRI agents can result in environmental pollution and organ accumulation. To address this, we introduce biocompatible and biodegradable polyphosphoesters, as MRI-traceable polymers using the ³¹P centers in the polymer backbone. We overcome challenges in ³¹P MRI, including background interference and low sensitivity, by modifying the molecular environment of ³¹P, assembling polymers into colloids, and tailoring the polymers' microstructure to adjust MRI-relaxation times. Specifically, gradient-type polyphosphonate-copolymers demonstrate improved MRI-relaxation times compared to homo- and block copolymers, making them suitable for imaging. We validate background-free imaging and biodegradation in vivo using Manduca sexta. Furthermore, encapsulating the potent drug PROTAC allows using these amphiphilic copolymers to simultaneously deliver drugs, enabling theranostics. This first report paves the way for polyphosphoesters as background-free MRI-traceable polymers for theranostic applications.

Confining the Sol-Gel Reaction at the Water/Oil Interface: Creating Compartmentalized Enzymatic Nano-Organelles for Artificial Cells

Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous-core silica nanocapsules. In order to confine the sol-gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi-permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme-carrying nanocapsules, as synthetic nano-organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.

Environment-friendly transesterification to seawater-degradable polymers expanded: Computational construction guide to breaking points

Marine plastic pollution caused by non-biodegradable polymers is a major worldwide concern. So-called "biodegradable" polymers should reduce plastic pollution in the environment by the safeguard of biodegradation. However, many polyesters degrade very slowly in seawater. We therefore designed a systematic library of "breaking points" that are installed into a polylactide backbone and simulated their degradation mechanisms, including internal and external S_N2 mechanisms, Addition-Elimination (AE) mechanisms, and RNA-inspired mechanisms. The breaking points are composed of phosphoesters with pendant nucleophiles directly at the P-atom, or structurally similar silicones, or side-chain functional polyesters. All P-containing breaking points react via the RNA-inspired mechanism, while Si-containing linkers undergo decomposition via the A-E mechanism. For C-containing linkers, only when a long pendant chain (4 carbon atoms) is present can the reaction proceed via the RNA-inspired mechanism. In cases of shorter pendants, the Addition-Elimination (AE) mechanism is energetically favorable. We believe that these calculations will pave the way for the synthesis of exceptionally seawater-degradable polyesters in the future that can act as a safeguard to prevent microplastic formation after eventual littering.

RNA-Inspired and Accelerated Degradation of Polylactide in Seawater

Marine plastic pollution is a worldwide challenge making advances in the field of biodegradable polymer materials necessary. Polylactide (PLA) is a promising biodegradable polymer used in various applications; however, it has a very slow seawater degradability. Herein, we present the first library of PLA derivatives with incorporated “breaking points” to vary the speed of degradation in artificial seawater from years to weeks. Inspired by the fast hydrolysis of ribonucleic acid (RNA) by intramolecular transesterification, we installed phosphoester breaking points with similar hydroxyethoxy side groups into the PLA backbone to accelerate chain scission. Sequence-controlled anionic ring-opening copolymerization of lactide and a cyclic phosphate allowed PLA to be prepared with controlled distances of the breaking points along the backbone. This general concept could be translated to other slowly degrading polymers and thereby be able to prevent additional marine pollution in the future.