Enhancing the Efficacy of Photodynamic Therapy through a Porphyrin/POSS Alternating Copolymer

Tannic acid and carboxymethyl chitosan-based multi-functional double-layered hydrogel with pH-stimulated response behavior for smart real-time infection monitoring and wound treatment

The dramatic increase of drug-resistant pathogenic bacteria has seriously effect on human health, appealing the needs of developing theranostic platforms with stimuli-responsive materials to realize the accurate bacterial diagnostics and therapeutics. Herein, a tannic acid and carboxymethyl chitosan-based multifunctional ZIF-90@i-PPOPs-phenol red double-layered hydrogel with stimuli-responsiveness and antibacterial activity was fabricated. The inner layer hydrogel (ZIF-90@i-PPOPs-based TFC hydrogels) was fabricated based on ZIF-90@i-PPOPs, integrate tannic acid and carboxymethyl chitosan linked by formylphenylboronic acid (FPBA), which exhibited outstanding injectable, biodegradability and antibacterial activity. The outer layer hydrogel (PR@PAM hydrogels) were constructed from polyacrylamide (PAM) and pH indicator phenol red, owning porous structure and excellent tissue adhesion. Due to the weakly acidic microenvironment within wound, the inner-layer hydrogel was stimulus-responsively decomposed, resulting in the accurate delivery of the positively charged ZIF-90@i-PPOPs to the lesion site to capture and kill bacteria by enhanced Zn2+ and ROS release. Meantime, the outer-layer hydrogel could real-timely monitor the pH changes to evaluate the wound recovery status. These double-layered hydrogels possessed precisely pH monitoring capacity, excellent antibacterial ability and negligible side effect to normal tissue in vivo, implying the high potential of the suggested hydrogels as theranostic platform for antibacterial treatment.

Imaging of Cancer Cells and Dictated Cytotoxicity Using Aptamer-Guided Hybridization Chain Reaction (HCR)-Generated G-Quadruplex Chains

DNA nanotechnology provides powerful tools for developing cancer theranostics. Here we introduce the autonomous surface-nucleolin-guided HCR that leads to the polymerization of G-quadruplex polymer chains, in which the Zn^II -protoporphyrin IX is intercalated. We demonstrate that MDA-MB-231 (Triple Negative Breast Cancer cells, TNBC) with overexpressed surface nucleolin were able to induce HCR leading to the formation of the Zn^II PPIX-loaded G-quadruplex polymer chains, while the M10 epithelial breast cells served as control. The Zn^II PPIX-loaded nanowires allow the selective imaging of TNBC, and their permeation into the TNBC leads to selective cytotoxicity and guided photodynamic therapy toward the cancer cells due to structural perturbation of the membranes. The aptamer-guided HCR-generated G-quadruplex polymer chains may serve as a versatile tool to target TNBC featuring poor prognosis and high pathological risk of recurrence, thus offering a promising theranostic platform.

Self-assembly of Amphiphilic Porphyrins To Construct Nanoparticles for Highly Efficient Photodynamic Therapy

Hydrophobic photosensitizers greatly affect cell permeability and enrichment in tumors, but they cannot be used directly for clinical applications because they always aggregate in water, preventing their circulation in the blood and accumulation in tumor cells. As a result, amphiphilic photosensitizers are highly desirable. Although nanomaterial-based photosensitizers can solve water solubility, they have the disadvantages of complicated operation, poor reproducibility, low drug loading, and poor stability. In this work, an efficient synthesis strategy is proposed that converts small molecules into nanoparticles in 100 % aqueous solution by molecular assembly without the addition of any foreign species. Three photosensitizers with triphenylphosphine units and ethylene glycol chains of different lengths, TPP-PPh₃ , TPP-PPh₃ -2PEG and TPP-PPh₃ -4PEG, were synthesized to improve amphiphilicity. Of the three photosensitizers, TPP-PPh₃ -4PEG is the most efficient (singlet oxygen yield: 0.89) for tumor photodynamic therapy not only because of its definite constituent, but also because its amphiphilic structure allows it to self-assemble in water.

Acid-Activatable Transmorphic Peptide-Based Nanomaterials for Photodynamic Therapy

Inspired by the dynamic morphology control of molecular assemblies in biological systems, we have developed pH-responsive transformable peptide-based nanoparticles for photodynamic therapy (PDT) with prolonged tumor retention times. The self-assembled peptide-porphyrin nanoparticles transformed into nanofibers when exposed to the acidic tumor microenvironment, which was mainly driven by enhanced intermolecular hydrogen bond formation between the protonated molecules. The nanoparticle transformation into fibrils improved their singlet oxygen generation ability and enabled high accumulation and long-term retention at tumor sites. Strong fluorescent signals of these nanomaterials were detected in tumor tissue up to 7 days after administration. Moreover, the peptide assemblies exhibited excellent anti-tumor efficacy via PDT in vivo. This in situ fibrillar transformation strategy could be utilized to design effective stimuli-responsive biomaterials for long-term imaging and therapy.

GSH-triggered release of sulfur dioxide gas to regulate redox balance for enhanced photodynamic therapy

Herein, a promising strategy is explored to regulate redox balance in tumor cells by simultaneously consuming GSH and releasing SO₂ gas for enhanced photodynamic therapy.

Acid-Triggered Nanoexpansion Polymeric Micelles for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) as a noninvasive and selective treatment technology has presented great potential in cancer prevention and precision medicine, but its therapeutic efficacy is still greatly inhibited by the limitations of photosensitizers (PSs) in the microenvironment such as the aggregation caused quenching (ACQ) of PSs. Herein, we proposed an "acid-triggered nanoexpansion" method to further reduce the aggregation of photosensitizers by constructing acetal-based polymeric micelles. A pH-responsive amphiphilic block copolymer, POEGMA-b-[PTTMA-co-PTPPC6MA] was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and self-assembled into spherical micelles. In the normal physiological environment, the micelles were stable and had good biocompatibility. Upon entry into the acidic microenvironment of the tumor, the acid-responsive hydrophobic 2, 4, 6-trimethoxybenzaldehyde in the micelles hydrolyzed and generated a hydrophilic diol moiety. Although the hydrophility of the micellar core was increased, the assembled structure of block copolymers was not dissociated but expanded. The responsive expansion of the micelles could allow the photosensitizers to well-disperse in the core, whereas more tumor-dissolved oxygen entered the micelles. This phenomenon could provide a better nanoenvironment for photosensitizers to reduce the ACQ of the photosensitizers, leading to more singlet oxygen (¹O₂) produced under the laser irradiation (650 nm). Both in vitro and in vivo studies have demonstrated that the remarkable photodynamic therapeutic efficacy of acid-responsive micelles could be realized. Thus, the acid-triggered nanoexpansion method might provide more possibilities to develop efficient platforms for treating cancers.