Poly(phenylene ethynylene) Conjugated Polyelectrolytes Synthesized via Chain-Growth Polymerization

A Perspective Looking Backward and Forward on the 25th Anniversary of Conjugated Polyelectrolytes

Conjugated polyelectrolytes are π-conjugated polymers that contain ionic charged groups such as sulfonate (R-SO3-), carboxylate (R-COO-), or ammonium (R-NR3+) combined with a π-conjugated backbone. This perspective provides a summary review of the key developments in the field, starting from the first reports of their synthesis and properties to application-focused developments. The applications include optical sensors for molecular and biomolecular targets, organic electronic applications, and specific biological applications including cellular imaging and photodynamic therapy. This perspective concludes with a discussion of where the field of conjugated polyelectrolytes is expected to lead in the coming years.

Self-Amplifying Nanotherapeutic Drugs Homing to Tumors in a Manner of Chain Reaction

Active tumor-targeting drug delivery has great potency in cancer therapy. However, the targeting efficiency of traditional active tumor-targeting nanotherapeutic drugs is limited by the scarcity of their accessible targets/receptors in tumors. Here, a novel self-amplifying tumor-targeting strategy with a chain reaction mechanism is developed. A coagulation targeting peptide (GNQEQVSPLTLLKXC, termed A15)-decorated poly(L-glutamic acid)-graft-maleimide poly(ethylene glycol)/combretastatin A4 conjugate (A15-PLG-CA4) is prepared to obtain a self-amplifying nanotherapeutic platform homing to tumors. After administration to tumor-bearing mice, A15-PLG-CA4 starts a chain reaction cycle consisting of intratumoral hemorrhage, target FXIIIa amplification, blood clot binding, and CA4 release in tumors. In this way, A15-PLG-CA4 increases the level of its accessible targets (FXIIIa) in a manner of chain reaction. The FXIIIa activity at 8 h is 4.1-fold more than the one at 0 h in the C26 tumors treated with A15-PLG-CA4. The total CA4 concentration at 24 h is 2.9-fold more than the control. A15-PLG-CA4 shows a significantly higher antitumor effect against large C26 tumors (≈500 mm3 ) thanks to the remarkable tumor-targeting ability compared with the control. Therefore, this report highlights the potential of the self-amplifying tumor-targeting strategy in the development of next generation active tumor-targeting nanotherapeutic drugs for tumor therapy.

Emerging theranostic gold nanostructures to combat cancer: Novel probes for Combinatorial Immunotherapy and Photothermal Therapy

The application of gold nanoparticles in immunotherapy has emerged as one of the most effective therapeutic strategy for eradicating cancer by releasing antigens, oligonucleotides, adjuvants, immune-stimulating agents into the body. Gold nanoparticles are found to be a superior choice, for generating attack on oncogenic cells, due to their low toxicity, better target specificity, diagnostic capabilities, and enhanced cellular uptake rate. This review focuses on the efficiency of several functionalized gold nanoparticles of diverse shapes and sizes as delivery vehicles to desired target cells through effective immunotherapy, along with a brief discussion about photothermal therapy.

Biofunctionalization of Water-Soluble poly(Phenylene Ethynylene)s

We report the use of amide coupling chemistry to covalently link five different biofunctional groups onto an anionic water-soluble poly(phenylene ethynylene) (PPE) polymer. Two of the biofunctionalized PPEs are used in prototype applications, including pH sensing and flow cytometry labeling. The PPE is functionalized with carboxylate (R-CO2-) and sulfonate (R-SO3-) ionic groups. By using an activated ester, the amine-functionalized groups are covalently linked to the PPE polymer via amide linkages. The reaction chemistry is optimized using biotin-ethylene diamine, making it possible to control the loading of the biotin functionality on the PPE chains. Using the optimized approach, a family of five PPEs were prepared that contain biotin, rhodamine, cholesterol, mannose, or folic acid moieties appended to the polymer backbones. The rhodamine- and biotin-modified PPEs were further applied for pH response and flow cytometry applications. The reported approach can be utilized for other classes of water-soluble conjugated polymers, allowing facile development of a variety of new functionalized water-soluble conjugated polymers for a range of applications including sensing, bioimaging, and flow cytometry analysis.

Aggregation-Enhanced Two-Photon Absorption of Anionic Conjugated Polyelectrolytes

The two-photon absorption properties of anionic poly(phenylene ethynylene)-type conjugated oligo- and polyelectrolytes are studied in molecularly dissolved and aggregated forms in aqueous solution. Several different polyvalent cations are used to induce aggregation. It is found that both materials in the aggregated form exhibit enhanced two-photon excited fluorescence (2PEF) and two-photon cross section (σ₂) compared with the molecularly dissolved structures. The 2PEF and σ₂ are unaffected by the nature of the polyvalent cation that is used to induce aggregation. The two-photon absorption cross section enhancement arises because of the increase in the difference dipole moment (Δμ) in the aggregates of the conjugated materials, an effect that is attributed to the introduction of charge transfer character into the aggregate excited state.

Near-Infrared-Light-Assisted in Situ Reduction of Antimicrobial Peptide-Protected Gold Nanoclusters for Stepwise Killing of Bacteria and Cancer Cells

Biomolecule-protected gold nanostructures show good performance in biomedical applications. However, precise control over gold nanocluster (AuNC) preparation with biomolecules remains challenging. Here, we develop a simple near-infrared (NIR)-light-assisted method for in situ reduction of antimicrobial peptide (AMP)-protected AuNCs. Take advantage of the high photothermal conversion efficiency of the conjugated polymer (CP) upon NIR light irradiation, we promote the rapid reduction of AuNCs by the AMP on the surface of the CP. The fluorescent properties of the AuNCs were improved owing to the formation of a unique Au(0)NC@Au(I)AMP core-shell nanostructure. This nanostructure is attributed to the rapid reduction of Au(0) and collision and fusion of Au(0) at high temperatures. Integrating antibacterial AMPs, fluorescent AuNCs, and photothermal CPs, the composites facilitated different killing mechanisms for both bacteria and cancer cells. This material system provides an all-in-one strategy for the stepwise killing of cancer cells and bacterial infection.