Three-Component Dynamic Covalent Chemistry: From Janus Small Molecules to Functional Polymers.

A new multicomponent reaction involving 2-hydroxybenzaldehyde, amine, and 2-mercaptobenzaldehyde (HAM reaction) has been developed and applied to multicomponent polymerization and controlled radical polymerization for the construction of random and block copolymers. This chemistry features mild reaction conditions, high yield, simple isolation, and water as the only byproduct. With the advantages of the distinct nucleophilicity of thiol and hydroxyl groups, the chemistry could be used for stepwise labeling and modifications on primary amines. The Janus chemical joint formed from this reaction exhibits degradability in buffers and generates the corresponding starting reagents, allowing amine release. Interestingly, the chemical joint exhibits thermally activated reversibility with water as the catalyst. This multicomponent dynamic covalent feature has been applied to the metamorphosis of random and block copolymers, generating polymers with diverse architectures. This chemistry is expected to be broadly applicable to synthetic polymer chemistry and materials science.

Covalent Labeling with an α,ß-Unsaturated Carbonyl Scaffold for Studying Protein Structure and Interactions by Mass Spectrometry.

A new covalent labeling (CL) reagent based on an α,ß-unsaturated carbonyl scaffold has been developed for studying protein structure and protein-protein interactions when coupled with mass spectrometry. We show that this new reagent scaffold can react with up to 13 different types of residues on protein surfaces, thereby providing excellent structural resolution. To illustrate the value of this reagent scaffold, it is used to identify the residues involved in the protein-protein interface that is formed upon Zn(II) binding to the protein ß-2-microglobulin. The modular design of the α,ß-unsaturated carbonyl scaffold allows facile variation of the functional groups, enabling labeling kinetics and selectivity to be tuned. Moreover, by introducing isotopically enriched functional groups into the reagent structure, labeling sites can be more easily identified by MS and MS/MS. Overall, this reagent scaffold should be a valuable CL reagent for protein higher order structure characterization by MS.

Cellular AND Gates: Synergistic Recognition to Boost Selective Uptake of Polymeric Nanoassemblies.

The development of nanoparticle-based biomedical applications has been hampered due to undesired off-target effects. Herein, we outline a cellular AND gate to enhance uptake selectivity, in which a nanoassembly-cell interaction is turned on, only in the concurrent presence of two different protein functions, an enzymatic reaction (alkaline phosphatase, ALP) and a ligand-protein (carbonic anhydrase IX, CA IX) binding event. Selective uptake of nanoassemblies was observed in cells that overexpress both of these proteins (unicellular AND gate). Interestingly, selective uptake can also be achieved in CA IX overexpressed cells, when cocultured with ALP overexpressed cells, where the nanoassembly presumably acts as a mediator for cell-cell communication (bicellular AND gate). This logic-gated cellular uptake could find use in applications such as tumor imaging or theranostics.

Cellular- and Subcellular-Targeted Delivery Using a Simple All-in-One Polymeric Nanoassembly.

Nanocarrier-mediated drug delivery is a promising strategy to maximize the power of chemotherapy and minimize side effects. However, current approaches show insufficient drug-loading capacity and inefficient drug release, and require complex modification processes. Attempts to enhance one of these features often compromise other merits. We describe here a block copolymer assembly system that combines desirable characteristics. The design of self-immolative and crosslinkable hydrophobic moieties offer stable and high encapsulation. Redox-triggerable polymer self-immolation promotes drug release by switching the hydrophobic core into completely hydrophilic chains. The reactive amine handles, presented on their surface, allow "plug to direct" modification with targeting ligands. Functionalized nanoassemblies have been programmed to target specific subcellular compartments. The simplicity, versatility, and efficacy of the system open up possibilities for an all-in-one delivery system.

Supramolecular Assemblies for Transporting Proteins Across an Immiscible Solvent Interface.

Polymeric supramolecular assemblies that can effectively transport proteins across an incompatible solvent interface are described. We show that electrostatics and ligand-protein interactions can be used to selectively transport proteins from an aqueous phase to organic phase. These transported proteins have been shown to maintain their tertiary structure and function. This approach opens up new possibilities for application of supramolecular assemblies in sensing, diagnostics and catalysis.

Biodistribution Analysis of NIR-Labeled Nanogels Using in Vivo FMT Imaging in Triple Negative Human Mammary Carcinoma Models.

The purpose of this study is to evaluate the biodistribution properties of random-copolymer-based core-cross-linked nanogels of various sizes and surface poly(ethylene glycol) composition. Systematic variations of near-IR labeled nanogels, comprising varying particle sizes (28-135 nm), PEG corona quantity (0-50 mol %), and PEG length (PEG Mn 1000, 2000, and 5000), were prepared and injected in mice that had been subcutaneously implanted with MDA-MB-231-luc-D3H2LN human mammary carcinoma. In vivo biodistribution was obtained using fluorescence molecular tomography imaging at 0, 6, 24, 48, and 72 h postinjection. Retention of total body probe and percentages of total injected dose in the tumor, liver, spleen, lungs, heart, intestines, and kidneys were obtained. Smaller nanogels (∼30-40 nm) with a high PEG conjugation (∼43-46 mol %) of Mn 2000 on their coronas achieved the highest tumor specificity with peak maximum 27% ID/g, a statistically significant propensity toward accumulation with 16.5% ID/g increase from 0 to 72 h of imaging, which constitutes a 1.5-fold increase. Nanogels with greater tumor localization also had greater retention of total body probe over 72 h. Nanogels without extensive PEGylation were rapidly excreted, even at similar sizes to PEGylated nanogels exhibiting whole body retention. Of all tissues, the liver had the highest % ID, however, like other tissues, it displayed a monotonic decrease over time, suggesting nanogel clearance by hepatic metabolism. Ex vivo quantification of individual tissues from gross necropsy at 72 h postinjection generally correlated with the FMT analysis, providing confidence in tissue signal segmentation in vivo. The parameters determined to most significantly direct a nanogel to the desired tumor target can lead to improve effectiveness for nanogels as therapeutic delivery vehicles.

Propagation of Enzyme-Induced Surface Events inside Polymer Nanoassemblies for a Fast and Tunable Response.

We report a new molecular design strategy that allows for the propagation of surface enzymatic events inside a supramolecular assembly for accelerated molecular release. The approach addresses a key shortcoming encountered with many of the currently available enzyme-induced disassembly strategies, which rely on the unimer-aggregate equilibria of amphiphilic assemblies. The enzymatic response of the host to predictably tune the kinetics of guest-molecule release can be programmed by controlling substrate accessibility through electrostatic complexation with a complementary polymer. Accelerated guest release in response to the enzyme is shown to be accomplished by a cooperative mechanism of enzyme-triggered supramolecular host disassembly and host reorganization.

Templated Self-Assembly of a Covalent Polymer Network for Intracellular Protein Delivery and Traceless Release.

Trafficking proteins inside cells is an emerging field with potential utility in basic cell biology and biological therapeutics. A robust and sustainable delivery strategy demands not only good protection of the cargo but also reversibility in conjugation and activity. We report a protein-templated polymer self-assembly strategy for forming a sheath around the proteins and then tracelessly releasing them in the cytosol. The versatility of the approach, demonstrated here, suggests that the strategy is compatible with a wide array of biologics.

Programmable Nanoassemblies from Non-Assembling Homopolymers Using Ad†Hoc Electrostatic Interactions.

Robust nanostructures were obtained from polymers that otherwise do not assemble by using a novel approach based on electrostatic self-assembly. The essence of this strategy involves the use of divalent counterions to temporarily perturb the packing features of the ionic groups in a homopolymer, which results in a vesicle-like structure that is captured in situ through a simple crosslinking reaction. The fidelity of the assembly has been tested for molecular transport across the nanomembrane, both for the molecules encapsulated in the lumen and for those trapped in the membrane itself. The membranes are addressable for robust multifunctionalization of their surfaces and for tunable transmembrane molecular transport.

Field Guide to Challenges and Opportunities in Antibody-Drug Conjugates for Chemists.

Antibody-drug conjugates have attracted a great amount of attention as a therapeutic strategy for diseases where targeting specific tissues and cells are critical components, such as in cancer therapy. Although promising, the number of approved ADC drugs is relatively limited. This emanates from the challenges associated with generating the conjugates and the complexities associated with the stability requirements for these conjugates during circulation and after reaching the target. Here, we provide a comprehensive overview of the design challenges facing the ADC field. These challenges also provide several unique research and development opportunities, which are also highlighted throughout the review.

Protein and enzyme gated supramolecular disassembly.

An amphiphilic nanoassembly was designed to respond to the concurrent presence of a protein and an enzyme. We present herein a system, where in the presence of these two stimuli supramolecular disassembly and molecular release occur. This molecular release arises in the form a fluorescence response that has been shown to be specific. We also show that this system can be modified to respond only if light stimulus is also present in addition to the protein and the enzyme. Demonstration of such supramolecular disassembly principles could have broad implications in a variety of biological applications.

Multi-stimuli responsive macromolecules and their assemblies.

In this review, we outline examples that illustrate the design criteria for achieving macromolecular assemblies that incorporate a combination of two or more chemical, physical or biological stimuli-responsive components. Progress in both fundamental investigation into the phase transformations of these polymers in response to multiple stimuli and their utilization in a variety of practical applications are highlighted. Using these examples, we aim to explain the origin of employed mechanisms of stimuli responsiveness which may serve as a guideline to inspire future design of multi-stimuli responsive materials.

Conferring liver selectivity to a thyromimetic using a novel nanoparticle increases therapeutic efficacy in a diet-induced obesity animal model.

Optimization of metabolic regulation is a promising solution for many pathologies, including obesity, dyslipidemia, type 2 diabetes, and inflammatory liver disease. Synthetic thyroid hormone mimics-based regulation of metabolic balance in the liver showed promise but was hampered by the low biocompatibility and harmful effects on the extrahepatic axis. In this work, we show that specifically directing the thyromimetic to the liver utilizing a nanogel-based carrier substantially increased therapeutic efficacy in a diet-induced obesity mouse model, evidenced by the near-complete reversal of body weight gain, liver weight and inflammation, and cholesterol levels with no alteration in the thyroxine (T4) / thyroid stimulating hormone (TSH) axis. Mechanistically, the drug acts by binding to thyroid hormone receptor ß (TRß), a ligand-inducible transcription factor that interacts with thyroid hormone response elements and modulates target gene expression. The reverse cholesterol transport (RCT) pathway is specifically implicated in the observed therapeutic effect. Overall, the study demonstrates a unique approach to restoring metabolic regulation impacting obesity and related metabolic dysfunctions.

Concurrent binding and delivery of proteins and lipophilic small molecules using polymeric nanogels.

Supramolecular nanoassemblies, which are capable of binding and delivering either lipophilic small molecules or hydrophilic molecules, are of great interest. Concurrently binding and delivering this combination of molecules is cumbersome, because of the opposing supramolecular host requirements. We describe the development of a versatile nanoassembly system that is capable of binding and delivering both, a protein and a lipophilic small molecule, simultaneously inside the cells.

Ligand-decorated nanogels: fast one-pot synthesis and cellular targeting.

Nanoscale vehicles for delivery have been of interest and extensively studied for two decades. However, the encapsulation stability of hydrophobic drug molecules in delivery vehicles and selective targeting these vehicles into disease cells are potential hurdles for efficient delivery systems. Here we demonstrate a simple and fast synthetic protocol of nanogels that shows high encapsulation stabilities. These nanogels can also be modified with various targeting ligands for active targeting. We show that the targeting nanogels (T-NGs), which are prepared within 2 h by a one-pot synthesis, exhibit very narrow size distributions and have the versatility of surface modification with cysteine-modified ligands including folic acid, cyclic arginine-glycine-aspartic acid (cRGD) peptide, and cell-penetrating peptide. T-NGs hold their payloads, undergo facilitated cell internalization by receptor-mediated uptake, and release their drug content inside cells due to the reducing intracellular environment. Selective cytotoxicity to cells, which have complementary receptors, is also demonstrated.

"Seminal testosterone", rising viewpoint of local spermatogenesis in nonobstructive azoospermia: One center long-term bidirectional cohort study.

Objective: Reproductive hormones are a traditional good method to evaluate spermatogenesis but might not accurately represent local spermatogenesis. To find a more accurate method, seminal reproductive hormones were studied. Methods: A bidirectional cohort study was performed. A total of 126 infertile men from 2018 to 2019 were retrospectively analyzed. They were divided into nonobstructive azoospermia (NOA), oligozoospermia (OLZ) and normal (NOR) groups. A prospective study was conducted on patients in the NOA and OLZ groups for 2 years. Microscopic testicular sperm extraction was performed for NOA patients, who were divided into a focal spermatogenesis group (FS) and an idiopathic azoospermia group (IA). Drug treatment was for OLZ patients, who were divided into a valid group (VA) and an invalid group (IN). The differences in sperm parameters and reproductive hormones were compared. ANOSIM analysis was used between and within groups. Pearson correlation analysis, CO inertia analysis and Proctor's analysis were for relationships. ROC curve for the specificity and sensitivity. Time series analysis was for the trends between hormones and time. Results: The b-FSH, b-LH, s-T and ΔT in the NOA group were significantly higher than those in the OLZ and NOR groups. However, the s-FSH, s-E2, s-P, ΔFSH, ΔLH, ΔP and ΔE2 were lower. Thirty-one NOA patients underwent MTSE, of whom 12 had sperm (FS) and 19 had no sperm (IA). The s-FSH and s-E2 of the FS group were higher than those of the IA group. Twenty-six OLZ patients completed 30 days of treatment, of which 11 had an improved sperm count (VA) and 15 had no (IN). The ΔT of the VA group was higher than that of the IN group. After follow-up for 2 years, 18 patients' results showed that b-FSH, b-LH and s-T were different over time, with delays of 19, 3 and -19 days. SC is closely related to pH, s-FSH, s-LH, s-E2, s-P, s-T, b-FSH, b-LH, ΔFSH, ΔLH, ΔP, ΔE2 and ΔT. There were complex common trends and relationships between different kinds of hormones. s-FSH, s-LH, s-E2, s-P, s-T, b-FSH and b-LH were useful to judge spermatogenesis, of which s-T, b-FSH and b-LH were more sensitive. If s-T, b-FSH and b-LH reached 64.4, 9.4 and 4.7, respectively, their prediction performance was the strongest. Conclusion: Seminal testosterone is sensitive for judging local spermatogenesis in nonobstructive azoospermia patients, which may be the direction of local spermatogenesis in nonobstructive azoospermia. Clinical trial registration: http://www.chictr.org.cn/index.aspx, identifier ChiCTR2200060463.

Evaluating an external quality assurance program for semen analysis in China during 2009-2020.

INTRODUCTION: Semen analysis (SA) plays a key role in guiding treatments of male reproductive diseases and infertility due to male factors; however, it remains challenging to conduct an accurate SA due to lack of standardization, highly subjective assessments, and problems with automated procedures. Therefore, quality assurance (QA) and teaching courses are essential for making the laboratory results more consistent. MATERIALS AND METHODS: The external quality assurance (EQA) scheme was organized by national human sperm bank technology training bases in Guangdong province in China between 2009 and 2020. Until 2020, 124 laboratories from China participated in the EQA program. The EQA scheme per year has been organized involving two semen aliquots for sperm concentration, two video recordings for motility, and two smears for sperm morphology. All samples used in the EQA scheme were obtained from different healthy donors or patients. RESULTS: We estimated that the median coefficient of variation (CV) of sperm concentration, ignoring the method used, was 26.6%. Using a 100 µm deep counting chamber led to a decreasing CV of 13.6%. For sperm motility, the median CV of nonprogressive motility was high (50.8%), but the CV of progressive motility (13.2%), immotile sperm (14.3%), and total motility (11.8%) were acceptable. The morphology assessment revealed large variability (44.4%) irrespective of the classification criteria. DISCUSSION: The reduction of interlaboratory variability is still a challenge during SA in China. Therefore, it is critical to increase awareness of joining EQA schemes and establish standardized training centers to follow WHO-recommended procedures toward Chinese standards.

Triblock-Diblock Composite Nanoassemblies with Sequentially Addressable Host-Guest Properties for Hydrophobics and Hydrophilics.

Noncovalent encapsulation of multiple guest molecules with distinct physiochemical properties, especially hydrophilic and hydrophobic guests, into a single polymeric nanoassembly is challenging, but would be profoundly beneficial to combination therapeutic delivery strategies. Here, we report a nanocomposite co-assembled by coating a layer of an amphiphilic block copolymer onto surface of a crosslinked inverse micelle driven by hydrophobic interactions. The hydrophobic coating layer and water-filled inverse micelles were utilized to encapsulate hydrophobic and hydrophilic cargos respectively. Rationally introducing the pH and redox responsive moieties into coating polymer and inverse micelles, allows sequentially addressing triggered release of the encapsulated cargos.

Polymer with Competing Depolymerization Pathways: Chain Unzipping versus Chain Scission.

Interest in triggered depolymerization is growing, driven by needs in sustainable plastics, self-healing materials, controlled release, and sensory amplification. For many triggered depolymerization reactions, the rate-limiting step does not directly involve the stimulus, and therefore, depolymerization kinetics exhibit only weak or no correlation to the concentration and reactivity of the stimulus. However, for many applications, a direct relationship between the stimulus and the depolymerization kinetics is desired. Here we designed, synthesized, and studied a polymer in which a nucleophile-induced chain scission (NICS) mechanism competes with the chain unzipping pathway. We find that the choice of the chain end functionality and the character of the nucleophile determines which of these is the predominant pathway. The NICS pathway was found to be dependent on the stimulus concentration, in contrast to the chain unzipping mechanism. We demonstrate transferability of these molecular-scale, structure-property relationships to nanoscale materials by formulating the polymers into host nanoparticles.

A programmable chemical switch based on triggerable Michael acceptors.

Developing an engineerable chemical reaction that is triggerable for simultaneous chemical bond formation and cleavage by external cues offers tunability and orthogonality which is highly desired in many biological and materials applications. Here, we present a chemical switch that concurrently captures these features in response to chemically and biologically abundant and important cues, viz., thiols and amines. This thiol/amine-triggerable chemical switch is based on a Triggerable Michael Acceptor (TMAc) which bears good leaving groups at its ß-position. The acceptor undergoes a "trigger-to-release" process where thiol/amine addition triggers cascaded release of leaving groups and generates a less activated acceptor. The newly generated TMAc can be further reversed to liberate the original thiol/amine by a second nucleophile trigger through a "trigger-to-reverse" process. Within the small molecular volume of the switch, we have shown five locations that can be engineered to achieve tunable "trigger-to-release" kinetics and tailored reversibility. The potential of the engineerable bonding/debonding capability of the chemical switch is demonstrated by applications in cysteine-selective and reversible protein modification, universal self-immolative linkers, and orthogonally addressable hydrogels.