Easy Access to Diverse Multiblock Copolymers with On-Demand Blocks via Thioester-Relayed In-Chain Cascade Copolymerization.

Multiblock copolymers are envisioned as promising materials with enhanced properties and functionality compared with their diblock/triblock counterparts. However, the current approaches can construct multiblock copolymers with a limited number of blocks but tedious procedures. Here, we report a thioester-relayed in-chain cascade copolymerization strategy for the easy preparation of multiblock copolymers with on-demand blocks, in which thioester groups with on-demand numbers are built in the polymer backbone by controlled/living polymerizations. These thioester groups further serve as the in-chain initiating centers to trigger the acyl group transfer ring-opening polymerization of episulfides independently and concurrently to extend the polymer backbone into multiblock structures. The compositions, number of blocks, and block degree of polymerization can be easily regulated. This strategy can offer easy access to a library of multiblock copolymers with ≈100 blocks in only 2 to 4 steps.

Synthesis of Poly(thioester sulfonamide)s via the Ring-Opening Copolymerization of Cyclic Thioanhydride with N-Sulfonyl Aziridine Using Mild Phosphazene Base.

Providing access to diverse polymer structures is highly desirable, which helps to explore new polymer materials. Poly(thioester sulfonamide)s, combining both the advantages of thioesters and amides, however, are rarely available in polymer chemistry. Here, the ring-opening copolymerization (ROCOP) of cyclic thioanhydride with N-sulfonyl aziridine using mild phosphazene base, resulting in well-defined poly(thioester sulfonamide)s with highly alternative structures, high yields, and controlled molecular weights, is reported. Additionally, benefiting from the mild catalytic process, this ROCOP can be combined with ROCOP of N-sulfonyl aziridines with cyclic anhydrides to produce novel block copolymers.

Interactions in DNA Condensation: An Important Factor for Improving the Efficacy of Gene Transfection.

The rapid developments of gene therapy are benefit from the construction of efficient gene vectors, which help therapy genes efficiently overcome the barriers in the transport and transfection. Condensing DNA into nanoparticles is a crucial role in gene transfection, and the electrostatic interactions of synthetic cationic liposomes and cationic polymers with DNA are generally used for condensing DNA. Recent research has shown that the introduction of the hydrophobic interaction, hydrogen bonding, and coordinative interactions to the gene delivery vectors is also very important for DNA condensation, delivery, and transfection. This review focuses on the four types of interactions in condensed DNA nanoparticles, which could provide a new perspective for improving gene transfection efficacy.

Precise Antibiotic Delivery to the Lung Infection Microenvironment Boosts the Treatment of Pneumonia with Decreased Gut Dysbiosis.

Bacterial pneumonia is a common disease with significant health risks. However, the overuse antibiotics in clinics face challenges such as inadequate targeting and limited drug utilization, leading to drug resistance and gut dysbiosis. Herein, a dual-responsive lung inflammatory tissue targeted nanoparticle (LITTN), designed for targeting lung tissue and bacteria, is screened from a series of prepared nanoparticles consisting of permanent cationic lipids, acid-responsive lipids, and reactive oxygen species-responsive and phenylboronic acid-modified lipids with different surface properties. Such nanoparticle is further verified to enhance the adsorption of vitronectin in serum. Additionally, the optimized nanoparticle exhibits more positive charge and coordination of boric acid with cis-diol in the infected microenvironment, facilitating electrostatic interactions with bacteria and biofilm penetration. Importantly, the antibacterial efficiency of dual-responsive rifampicin-loaded LITTN (Rif@LITTN) against methicillin-resistant staphylococcus aureus is 10 times higher than that of free rifampicin. In a mouse model of bacterial pneumonia, the intravenous administration of Rif@LITTN could precisely target the lungs, localize in the lung infection microenvironment, and trigger the responsive release of rifampicin, thereby effectively alleviating lung inflammation and reducing damage. Notably, the targeted delivery of rifampicin helps protect against antibiotic-induced changes in the gut microbiota. This study establishes a new strategy for precise delivery to the lung-infected microenvironment, promoting treatment efficacy while minimizing the impact on gut microbiota. STATEMENT OF SIGNIFICANCE: Intravenous antibiotics play a critical role in clinical care, particularly for severe bacterial pneumonia. However, the inability of antibiotics to reach target tissues causes serious side effects, including liver and kidney damage and intestinal dysbiosis. Therefore, achieving precise delivery of antibiotics is of great significance. In this study, we developed a novel lung inflammatory tissue-targeted nanoparticle that could target lung tissue after intravenous administration and then target the inflammatory microenvironment to trigger dual-responsive antibiotics release to synergistically treat pneumonia while maintaining the balance of gut microbiota and reducing the adverse effects of antibiotics. This study provides new ideas for targeted drug delivery and reference for clinical treatment of pneumonia.

An adhesion-switchable hydrogel dressing for painless dressing removal without secondary damage.

Hydrogels with strong adhesion to wet tissues are considered promising for wound dressings. However, the clinical application of adhesive hydrogel dressing remains a challenge due to the issues of secondary damage during dressing changes. Herein, we fabricated an adhesion-switchable hydrogel formed with poly(acrylamide)-co-poly(N-isopropyl acrylamide), quaternary ammonium chitosan and tannic acid. This hydrogel forms instant and robust adhesion to the skin at body temperature. However, as the temperature rises above the lower critical solution temperature (LCST), the hydrogel loses its adhesion towards the wound area due to the temperature-dependent volume phase transition of the copolymer, occurring around 45 °C. Consequently, the designed hydrogel can be easily detached from adhered tissues upon demand, providing a facile and effective method for painless dressing changes without secondary damage. This hydrogel holds great promise for long-term application in wound dressings.

Nanogalvanic Cells Release Highly Reactive Electrons in Tumors to Effectively Eliminate Tumors.

External stimuli triggering chemical reactions in cancer cells to generate highly reactive chemical species are very appealing for cancer therapy, in which external irradiation activating sensitizers to transfer energy or electrons to surrounding oxygen or other molecules is critical for generating cytotoxic reactive species. However, poor light penetration into tissue, low activity of sensitizers, and reliance on oxygen supply restrict the generation of cytotoxic chemical species in hypoxic tumors, which lowers the therapeutic efficacy. Here, this work presents galvanic cell nanomaterials that can directly release highly reactive electrons in tumors without external irradiation or photosensitizers. The released reactive electrons directly react with surrounding biomolecules such as proteins and DNA within tumors to destroy them or react with other surrounding (bio)molecules to yield cytotoxic chemical species to eliminate tumors independent of oxygen. Administering these nanogalvanic cells to mice results in almost complete remission of subcutaneous solid tumors and deep metastatic tumors. The results demonstrate that this strategy can further arouse an immune response even in a hypoxic environment. This method offers a promising approach to effectively eliminate tumors, similar to photodynamic therapy, but does not require oxygen or irradiation to activate photosensitizers.

Clinical value of perivascular fat attenuation index and computed tomography derived fractional flow reserve in identification of culprit lesion of subsequent acute coronary syndrome.

Purpose: To explore the potential of perivascular fat attenuation index (FAI) and coronary computed tomography angiography (CCTA) derived fractional flow reserve (CT-FFR) in the identification of culprit lesion leading to subsequent acute coronary syndrome (ACS). Methods: Thirty patients with documented ACS event who underwent invasive coronary angiography (ICA) from February 2019 to February 2021 and had received CCTA in the previous 6 months were collected retrospectively. 40 patients with stable angina pectoris (SAP) were matched as control group according to sex, age and risk factors. The study population has a mean age of 59.3 ± 12.3 years, with a male prevalence of 81.4%. The plaque characteristics, perivascular fat attenuation index (FAI), and coronary computed tomography angiography-derived fractional flow reserve (CT-FFR) of 32 culprit lesions and 30 non-culprit lesions in ACS patients and 40 highest-grade stenosis lesions in SAP patients were statistically analyzed. Results: FAI around culprit lesions was increased significantly (-72.4 ± 3.2 HU vs. -79.0 ± 7.7 HU, vs. -80.4 ± 7.0HU, all p < 0.001) and CT-FFR was decreased for culprit lesions of ACS patients [0.7(0.1) vs. 0.8(0.1), vs.0.8(0.1), p < 0.001] compared to other lesions. According to multivariate analysis, diameter stenosis (DS), FAI, and CT-FFR were significant predictors for identification of the culprit lesion. The integration model of DS, FAI, and CT-FFR showed the significantly highest area under the curve (AUC) of 0.917, compared with other single predictors (all p < 0.05). Conclusions: This study proposes a novel integrated prediction model of DS, FAI, and CT-FFR that enhances the diagnostic accuracy of traditional CCTA for identifying culprit lesions that trigger ACS. Furthermore, this model also provides improved risk stratification for patients and offers valuable insights for predicting future cardiovascular events.

H2S-removing UiO-66 MOFs for sensitized antibacterial therapy.

Antibiotic tolerance is implicated in difficult-to-treat infections and the development and spread of antibiotic resistance. The high storage capacities and excellent biocompatibilities of UiO-66-based metal-organic frameworks (MOFs) have made them emerging candidates as drug-delivery vectors. In view of hydrogen sulfide (H2S) having been associated with the development of intrinsic resistance to antibacterial agents, we designed a strategy to potentiate existing antibiotics by eliminating bacterial endogenous H2S. We efficiently fabricated an antibiotic enhancer Gm@UiO-66-MA to remove bacterial H2S and sensitize an antibacterial by modifying UiO-66-NH2 with maleic anhydride (MA) and then loading it with gentamicin (Gm). UiO-66-MA achieved the removal of bacterial endogenous H2S and the destruction of bacterial biofilm by selectively undergoing Michael addition with H2S. Moreover, Gm@UiO-66-MA further enhanced the susceptibility of tolerant E. coli to Gm after reducing bacterial intracellular H2S levels. An in vivo skin wound healing experiment confirmed that Gm@UiO-66-MA could greatly reduce the risk of bacterial reinfection and accelerate wound healing. Overall, Gm@UiO-66-MA offers a promising antibiotic sensitizer for minimizing bacterial resistance and a therapeutic strategy for tolerant bacteria-related refractory infections.

DPA-Zinc around Polyplexes Acts Like PEG to Reduce Protein Binding While Targeting Cancer Cells.

Gene therapy holds great promise as an effective treatment for many diseases of genetic origin. Gene therapy works by employing cationic polymers, liposomes, and nanoparticles to condense DNA into polyplexes via electronic interactions. Then, a therapeutic gene is introduced into target cells, thereby restoring or changing cellular function. However, gene transfection efficiency remains low in vivo due to high protein binding, poor targeting ability, and substantial endosomal entrapment. Artificial sheaths containing PEG, anions, or zwitterions can be introduced onto the surface of gene carriers to prevent interaction with proteins; however, they reduce the cellular uptake efficacy, endosomal escape, targeting ability, thereby, lowering gene transfection. Here, it is reported that linking dipicolylamine-zinc (DPA-Zn) ions onto polyplex nanoparticles can produce a strong hydration water layer around the polyplex, mimicking the function of PEGylation to reduce protein binding while targeting cancer cells, augmenting cellular uptake and endosomal escape. The polyplexes with a strong hydration water layer on the surface can achieve a high gene transfection even in a 50% serum environment. This strategy provides a new solution for preventing protein adsorption while improving cellular uptake and endosomal escape.

Co-delivery of a tumor microenvironment-responsive disulfiram prodrug and CuO2 nanoparticles for efficient cancer treatment.

Disulfiram (DSF) has been used as a hangover drug for more than seven decades and was found to have potential in cancer treatment, especially mediated by copper. However, the uncoordinated delivery of disulfiram with copper and the instability of disulfiram limit its further applications. Herein, we synthesize a DSF prodrug using a simple strategy that could be activated in a specific tumor microenvironment. Poly amino acids are used as a platform to bind the DSF prodrug through the B-N interaction and encapsulate CuO2 nanoparticles (NPs), obtaining a functional nanoplatform Cu@P-B. In the acidic tumor microenvironment, the loaded CuO2 NPs will produce Cu2+ and cause oxidative stress in cells. At the same time, the increased reactive oxygen species (ROS) will accelerate the release and activation of the DSF prodrug and further chelate the released Cu2+ to produce the noxious copper diethyldithiocarbamate complex, which causes cell apoptosis effectively. Cytotoxicity tests show that the DSF prodrug could effectively kill cancer cells with only a small amount of Cu2+ (0.18 µg mL-1), inhibiting the migration and invasion of tumor cells. In vitro and in vivo experiments have demonstrated that this functional nanoplatform could kill tumor cells effectively with limited toxic side effects, showing a new perspective in DSF prodrug design and cancer treatment.

Evolving deep convolutional neural networks by IP-based marine predator algorithm for COVID-19 diagnosis using chest CT scans.

This paper proposes an optimal structured deep convolutional neural network (DCNN) based on the marine predator algorithm (MPA) to construct a novel automatic diagnosis platform that may help radiologists identify COVID-19 and non-COVID-19 patients based on CT scan categorization and analysis. The goal is met with the help of three modifications based on the regular MPA. First, a novel encoding scheme based on Internet Protocol (IP) addresses is proposed, followed by introducing an Enfeebled layer to build a variable-length DCNN. Finally, the learning process divides big datasets into smaller chunks that are randomly evaluated. The proposed model is compared to the COVID-CT and SARS-CoV-2 datasets to undertake a complete evaluation. Following that, the performance of the developed model (DCNN-IPMPA) is compared to that of a typical DCNN and seven variable-length models using five well-known comparison metrics, as well as the receiver operating characteristic and precision-recall curves. The results show that the DCNN-IPMPA outperforms other benchmarks, with a final accuracy of 97.21% on the SARS-CoV-2 dataset and 97.94% on the COVID-CT dataset. Also, timing analysis indicates that the DCNN processing time is the best among all benchmarks as expected; however, DCNN-IPMPA represents a competitive result compared to the standard DCNN.

Cyclic topology enhances the killing activity of polycations against planktonic and biofilm bacteria.

Bacterial biofilms, as a fortress to protect bacteria, enhance resistance to antibiotics because of their limited penetration, which has become a major threat to current anti-infective therapy. Antimicrobial polycations have received wide attention to kill planktonic bacteria because of their unique antimicrobial mechanism without drug resistance but it is still hard to kill the bacteria in the deep of the biofilm. Unlike linear polymers, the cyclic topology has been demonstrated with enhanced penetration in tissues, which is attributed to the lack of end groups, constrained conformation and a smaller hydrodynamic volume, opening a new sight of polycations in the antibacterial application against biofilms. Here, polycations with different topologies including linear and cyclic polycations were synthesized and their killing activity against planktonic and biofilm bacteria was studied. The experimental results showed the enhanced antibacterial activity of cyclic polycations for planktonic bacteria, which is presumably attributed to their smaller hydrodynamic volume, higher local density of positive charge and more interactions between cation units and the bacterial membrane than their linear analogues. Besides, cyclic polycations exhibit enhanced killing effect for biofilm bacteria and inhibition effect for biofilms with 5-7 times and 2-3 times enhancements than the linear polycations, respectively. Furthermore, an Escherichia coli infection model on mice was established and the therapeutic effects of cyclic and linear polycations were evaluated. Compared with the linear polycations, the cyclic polycations exhibited enhanced antibacterial activity with an ∼4 times increase, promoting the healing of the infected wounds. This work provides a new perspective in the development of antimicrobial polycations, which are promising therapeutic agents to kill planktonic and biofilm bacteria without drug resistance.

Phenylboronic acid-functionalized silver nanoparticles for highly efficient and selective bacterial killing.

With the widespread use of antibiotics, the number of severe infections caused by unknown pathogens is increasing and novel antibacterial agents with high antibacterial efficiency and selective bacterial killing are urgently needed. In this work, we developed a new kind of functional material based on silver nanoparticles (AgNPs), whose surfaces were functionalized with phenylboronic acid (AgNPs-PBAn). The phenylboronic acid groups on the surface of AgNPs-PBAn could form covalent bonds with the cis-diol groups of lipopolysaccharide or teichoic acid on the bacterial surface, which highly promoted the interaction between AgNPs-PBAn and bacteria, resulting in a very strong enhancement of their antibacterial action via membrane disruption. The scanning electron microscopy images revealed that the accumulation of phenylboronic acid-functionalized AgNPs on the bacterial surface is much more than that of the nonfunctionalized AgNPs. Importantly, the antibacterial efficiency of the phenylboronic acid-functionalized AgNPs on a series of bacteria is 32 times higher than that of bare AgNPs. Moreover, AgNPs-PBAn showed a high selectivity toward bacteria with an IC50 (half maximal inhibitory concentration to mammalian cells) more than 160 times its MBC (minimum bactericidal concentration). In a model of an E. coli-infected wound in vivo, AgNPs-PBAn could effectively kill the bacteria with an accelerated wound healing rate. This study demonstrates that phenylboronic acid surface functionalization is an efficient way to drastically promote the antibacterial activity of AgNPs, improving the selectivity of silver-based nanoparticles against a variety of bacteria.

Biodegradable hydrogels with photodynamic antibacterial activity promote wound healing and mitigate scar formation.

Bacterial proliferation and the disordered extracellular matrix (ECM) at the wound site are the major reasons for delayed healing and abnormal scarring. The development of new multifunctional dressing materials that can effectively prevent scar formation without delaying wound healing remains a challenge. In this study, we construct a verteporfin-loaded biodegradable hydrogel (VP-gel) using hyaluronic acid and thiol-terminated 4-arm polyethylene glycol (PEG). The injectable VP-gel sustainably releases small doses of verteporfin in the wound microenvironment that generates reactive oxygen species (ROS) under red light irradiation to kill bacteria efficiently. Importantly, the sustained release of VP could also regulate TGF-ß family-induced cellular responses and the downstream signaling molecule Smad2 in fibroblasts to reduce myofibroblast differentiation, promoting ECM reconstruction and scarless wound healing. Immunohistochemical examination of wound healing and histomorphology in a mouse full-thickness wound model demonstrates excellent acceleration effects of VP-gel for infected wound healing. Therefore, VP-gel with anti-scarring and antibacterial activity, as well as enhanced infection wound healing ability shows great potential in the clinical treatment of scar healing for infected wounds.

Tumor Microenvironment Triggered the In Situ Synthesis of an Excellent Sonosensitizer in Tumor for Sonodynamic Therapy.

An ultrasound-triggered sonodynamic therapy has shown great promise for cancer therapy. However, its clinical applications are very limited because the traditional sonosensitizers tend to suffer from very poor efficiency combined with low retention in cancer cells and low tumor selectivity. Therefore, sonosensitizers with higher effectivity, higher tumor cell retention, and higher tumor cell specificity are highly required. Herein, we constructed a Ti2C(OH)X nanosheet, which was a poor sonosensitizer but had a long circulation in the blood system. However, it was very interesting to find that the tumor microenvironment could in situ turn Ti2C(OH)X nanosheet into a novel and excellent sonosensitizer with a nanofiber structure in tumors, exhibiting excellent ability to generate reactive oxygen species (ROS) under ultrasound. Moreover, the nanofiber structure made it very difficult to get out of cancer cells, highly enhancing the retention of the sonosensitizer in the tumor, thereby enabling it to effectively and selectively kill cancer cells in vivo. Our findings demonstrate that the strategy of the tumor microenvironment triggering the in situ synthesis of an effective sonosensitizer in tumor provided a promising means to simultaneously increase the efficiency, sonosensitizer retention in cancer cells, and cancer selectivity, thereby effectively killing cancer cells but causing little damage to healthy tissues via the sonodynamic therapy.

Charge-reversal silver clusters for targeted bacterial killing.

Bacterial infections have become a common global health problem, causing a wide range of properties and life loss. The development of a highly efficient, low-toxicity and targeted bacterial agent is urgently needed. As a conventional antibacterial agent, silver nanoparticles have been used for a long time, but they are still unable to achieve targeted bacterial killing. Herein, we have prepared surface positively (Ag(+) nanoparticles) and negatively (Ag(-) nanoparticles) charged silver nanoparticles by reduction of AgNO3 to construct Ag(-)/Ag(+) clusters. The zeta potential of the Ag(-)/Ag(+) nanoclusters could be controlled by changing the ratio of Ag(-) nanoparticles to Ag(+) nanoparticles. The surface negatively changed silver nanoparticles were prepared from the reaction of methyl maleic anhydride with the amino on the surface positively changed silver nanoparticles. In the acidic environment, Ag(-) nanoparticles undergo charge reversal, and Ag(-)/Ag(+) clusters with negatively charged nanoparticles and big-size are transformed into positively charged nanoparticles with small size. The in vitro experimental results demonstrate that the positively charged nanoparticles can be well adsorbed on the negatively charged bacteria, exhibiting a high bactericidal ability. Furthermore, the in vivo skin wound healing experiment showed that the Ag(-)/Ag(+) clusters could serve as an efficient antibacterial agent to combat bacterial infection.

Photopolymerization performed under dark conditions using long-stored electrons in carbon nitride.

In nature, the chemical energy and electrons stored in ATP and NADPH generated during irradiation can facilitate biochemical reactions under dark conditions. However, in artificial photoreaction systems, it is still very difficult to perform photoreactions under dark conditions due to the fact that the photogenerated charge pairs can recombine immediately upon ceasing the irradiation. Preventing the recombination of photogenerated charge pairs still constitutes a major challenge at present. Here, it is reported that functionalized carbon nitride nanomaterials having many heptazine rings with a positive charge distribution, which can tightly trap photogenerated electrons, efficiently prevent the recombination of photogenerated charges. These stored charges are exceedingly long-lived (up to months) and can drive photopolymerization without light irradiation, even after one month. The system introduced here demonstrates a new approach for storing light energy as long-lived radicals, enabling photoreactions under dark conditions.

Tug-of-War between Covalent Binding and Electrostatic Interaction Effectively Killing E. coli without Detectable Resistance.

Antimicrobial resistance in Gram-negative bacteria has become one of the leading causes of morbidity and mortality and a serious worldwide public health concern due to the fact that Gram-negative bacteria have an additional outer membrane protecting them from an unwanted compound invading. It is still very difficult for antimicrobials to reach intracellular targets and very challenging to treat Gram-negative bacteria with the current strategies. Here, we found that (o-(bromomethyl)phenyl)boronic acid was incorporated into poly((2-N,N-diethyl)aminoethyl acrylate) (PDEA), forming a copolymer (poly(o-Bn-DEA)) having both phenylboronic acid (B) and ((2-N,N-diethyl)amino) (DEA) units. Poly(o-Bn-DEA) exhibits very strong intramolecular B-N coordination, which could highly promote the covalent binding of phenylboronic acid with lipopolysaccharide (LPS) on the outer membrane of E. coli and lodge poly(o-Bn-DEA) on the LPS layer on the surface of E. coli. Meanwhile, the strong electrostatic interaction between poly(o-Bn-DEA) and the negatively charged lipid preferred tugging the poly(o-Bn-DEA) into the lipid bilayer of E. coli. The combating interactions between covalent binding and electrostatic interaction form a tug-of-war action, which could trigger the lysis of the outer membrane, thereby killing Gram-negative E. coli effectively without detectable resistance.

Single nanosheet can sustainably generate oxygen and inhibit respiration simultaneously in cancer cells.

In a tumor, the abnormal cancer cell proliferation results in an insufficient O2 supply, and meanwhile cancer cells consume O2 very fast. The imbalance between a low oxygen supply and overwhelming oxygen consumption results in a low oxygen concentration in solid tumors. Therefore, in order to relieve hypoxia in tumors, it is necessary to not only sustainably generate O2, but also inhibit mitochondrial respiration simultaneously. Here, we found that a single Ti2C(OH)2 nanomaterial not only can sustainably generate O2 but also simultaneously highly inhibits mitochondrial respiration via binding phosphorylation proteins onto the surface in cancer cells. Ce6 was linked onto Ti2C(OH)2, forming Ti2C(OH)2-Ce6. Ti2C(OH)2-Ce6 could highly relieve hypoxia in tumors via the combination of sustainable O2 generation and respiration inhibition, produce enough 1O2 to kill cancer cells via PDT, and also effectively convert the absorbed light energy into thermal energy to kill cancer cell via PTT, thereby highly enhancing the cancer therapy.

Correction: Single nanosheet can sustainably generate oxygen and inhibit respiration simultaneously in cancer cells.

Correction for 'Single nanosheet can sustainably generate oxygen and inhibit respiration simultaneously in cancer cells' by Wei-Qiang Huang et al., Mater. Horiz., 2021, DOI: .