Red Fluorescence from Organic Microdots: Leveraging Foldamer-Linked Azobenzene for Enhanced Stability and Intensity in Bioimaging Applications.

Azobenzene, while relevant, has faced constraints in biological system applications due to its suboptimal quantum yield and short-wavelength emission. This study presents a pioneering strategy for fabricating organic microdots by coupling foldamer-linked azobenzene, resulting in robust fluorescence intensity and stability, especially in aggregated states, thereby showing promise for bioimaging applications. Comprehensive experimental and computational examinations elucidate the mechanisms underpinning enhanced photostability and fluorescence efficacy. In vitro and in vivo evaluations disclose that the external layer of cis-azo-foldamer microdots performs a self-sacrificial function during photo-bleaching. Consequently, these red-fluorescent microdots demonstrate extraordinary structural and photochemical stabilities over extended periods. The conjugation of a ß-peptide foldamer to the azobenzene chromophore through a glycine linker instigates a blue-shifted and amplified π*-n transition. Molecular dynamics simulations reveal that the aggregated state of cis-azo-foldamers fortifies the stability of cis isomers, thereby augmenting fluorescence efficiency. This investigation furnishes crucial insights into conceptualizing novel, biologically inspired materials, promising stable and enduring imaging applications, and carries implications for diverse arenas such as medical diagnostics, drug delivery, and sensing technologies.

Simultaneous coupling of metal removal and visual detection by nature-inspired polyphenol-amine surface chemistry.

The interplay between polyphenols, amines, and metals has broad implications for surface chemistry, biomaterials, energy storage, and environmental science. Traditionally, polyphenol-amine combinations have been recognized for their ability to form adhesive, material-independent thin layers that offer a diverse range of surface functionalities. Herein, we demonstrate that a coating of tannic acid (TA) and polyethyleneimine (PEI) provides an efficient platform for capturing and monitoring metal ions in water. A unique feature of our PEI/TA-coated microbeads is the 'Detection-Capture' (Detec-Ture) mechanism. The galloyl groups in TA coordinate with Fe(III) ions (capture), initiating their oxidation to gallol-quinone. These oxidized groups subsequently react with PEI amines, leading to the formation of an Fe(II/III)-gallol-PEI network that produces a vivid purple color, thereby enabling visual detection. This mechanism couples metal capture directly with detection, distinguishing our approach from existing studies, which have either solely focused on metal removal or metal detection. The metal capturing capacity of our materials stands at 0.55 mg g-1, comparable to that of established materials like alginate and wollastonite. The detection sensitivity reaches down to 0.5 ppm. Our findings introduce a novel approach to the utility of metal-polyphenol-amine networks, presenting a new class of materials suited for simultaneous metal ion detection and capture in environmental applications.

Ferritin Nanoshuttle for Long-Lasting Self-Healing of Phenolic Hydrogels.

Herein, we highlight a novel finding that ferritin can play a crucial role in the "self-healing lifetime" of soft phenolic materials. Ferritin interacts with a catechol-functionalized polymer to form a self-healable and adhesive hydrogel bidirectionally by providing and retrieving Fe3+. As a result of its unique role as a nanoshuttle to store and release iron, ferritin significantly increases the self-healing lifetime of the hydrogel compared with that afforded by catechol-Fe3+ coordination through direct Fe3+ addition without ferritin. Ferritin also induces stable oxidative coupling between catechol moieties following metal coordination, which contributes to double cross-linking networks of catechol-catechol adducts and catechol-Fe3+ coordination. Thus, ferritin-mediated cross-linking can provide phenolic hydrogels with the advantages of hydrogels prepared by both metal coordination and oxidative coupling, thereby overcoming the limitations of the current cross-linking methods of phenolic hydrogels and broadening their versatility in biomedical applications.

Distinguishing between DNA-Loaded Full and Empty Capsids of Adeno-Associated Virus with Atomic Force Microscopy Imaging.

Recently, miraculous therapy approaches involving adeno-associated virus (AAV) for incurable diseases such as spinal muscular atrophy and inherited retinal dysfunction have been introduced. Nonreplicative, nonpathogenic, low rates of chromosome insertional properties and the existence of neutralizing antibodies are main safety reasons why the FDA approved its use in gene delivery. To date, AAV production always results in a mixture of nontherapeutic (empty) and therapeutic (DNA-loaded) full capsids (10-98%). Such existence of empty viral particles inevitably increases viral doses to human. Thus, the rapid monitoring of empty capsids and reducing the empty-to-full ratio are critical in AAV science. However, transmission electron microscopy (TEM) is the primary tool for distinguishing between empty and full capsids, which creates a research bottleneck because of instrument accessibility and technical difficulty. Herein, we demonstrate that atomic force microscopy (AFM) can be an alternative tool to TEM. The simple, noncontact-mode imaging of AAV particles allows the distinct height difference between full capsids (∼22 nm) and empty capsids (∼16 nm). The sphere-to-ellipsoidal morphological distortion observed for empty AAV particles clearly distinguishes them from full AAV particles. Our study indicates that AFM imaging can be an extremely useful, quality-control tool in AAV particle monitoring, which is beneficial for the future development of AAV-based gene therapy.

Phototoxicity-free blue light for enhancing therapeutic angiogenic efficacy of stem cells.

Low-level light therapy (LLLT) is a safe and noninvasive technique that has drawn attention as a new therapeutic method to treat various diseases. However, little is known so far about the effect of blue light for LLLT due to the generation of reactive oxygen species (ROS) that can cause cell damage. We introduced a blue organic light-emitting diode (bOLED) as a safe and effective light source that could generate a low amount of heat and luminance compared to conventional light sources (e.g., light-emitting diodes). We compared phototoxicity of bOLED light with different light fluences to human adipose-derived stem cells (hADSC). We further explored molecular mechanisms involved in the therapeutic efficacy of bOLED for enhancing angiogenic properties of hADSC, including intracellular ROS control in hADSCs. Using optimum conditions of bOLED light proposed in this study, photobiomodulation and angiogenic properties of hADSCs were enhanced. These findings might open new methods for using blue light in LLLT. Such methods can be implemented in future treatments for ischemic disease.

Antagonistically Functionalized Diatom Biosilica for Bio-Triboelectric Generators.

Although biomaterial-based triboelectric nanogenerators (Bio-TENGs) for use in wearable electronics and implantable sensors have been developed, power generation is not suitable for satisfying the basic requirements for practical applications. Here, to greatly enhance output performances of Bio-TENG devices, an antagonistic approach of diatom frustules (DFs) with amine and fluorine chemical functionalizations is reported. The DFs are treated with piranha solution to increase the density of hydroxyl groups and tribo-positive and tribo-negative composite films are designed with antagonistically functionalized DFs. The tribo-positive composites having electron donating functionality consist of aminated DFs and cellulose nanocrystals (CNCs), while the tribo-negative composite is composed of fluorinated DFs and polydimethylsiloxane (PDMS). An antagonistically and chemically functionalized TENG (ACF TENG) with an efficient contact area of 9.6 cm2 under a force of 8 N and a frequency of 5 Hz exhibits an output voltage of 248 V, a short-circuit current of 16.4 µA, and a power density of 2.01 W m-2 , which is 16.6 times higher than a reference (CNC:PDMS) TENG. This study shows a simple antagonistic approach for chemical functionalization as an efficient method to manipulate the tribo-polarity of bio-additives for enhancing power generation of Bio-TENGs.

Generalized Approach towards Secretion-Based Protein Production via Neutralization of Secretion-Preventing Cationic Substrate Residues.

Many heterologous proteins can be secreted by bacterial ATP-binding cassette (ABC) transporters, provided that they are fused with the C-terminal signal sequence, but some proteins are not secretable even though they carry the right signal sequence. The invention of a method to secrete these non-secretable proteins would be valuable both for understanding the secretory physiology of ABC transporters and for industrial applications. Herein, we postulate that cationic "supercharged" regions within the target substrate protein block the secretion by ABC transporters. We also suggest that the secretion of such substrate proteins can be rescued by neutralizing those cationic supercharged regions via structure-preserving point mutageneses. Surface-protruding, non-structural cationic amino acids within the cationic supercharged regions were replaced by anionic or neutral hydrophilic amino acids, reducing the cationic charge density. The examples of rescued secretions we provide include the spike protein of SARS-CoV-2, glutathione-S-transferase, streptavidin, lipase, tyrosinase, cutinase, growth factors, etc. In summary, our study provides a method to predict the secretability and a tool to rescue the secretion by correcting the secretion-blocking regions, making a significant step in understanding the physiological properties of ABC transporter-dependent protein secretion and laying the foundation for the development of a secretion-based protein-producing platform.

Material-Independent Surface Chemistry beyond Polydopamine Coating.

Various methods have been developed in surface chemistry to control interface properties of a solid material. A selection rule among surface chemistries is compatibility between a surface functionalization tool and a target material. For example, alkanethiol deposition on noble metal surfaces, widely known as the formation of a self-assembled monolayer (SAM), cannot be performed on oxide material surfaces. One must choose organosilane molecules to functionalize oxide surfaces. Thus, the surface chemistry strictly depends on the properties of the surface. Polydopamine coating is now generally accepted as the first toolbox for functionalization of virtually any material surface. Layer-by-layer (LbL) assembly is a widely used method to modify properties of versatile surfaces, including organic materials, metal oxides, and noble metals, along with polydopamine coating. On flat solid substrates, the two chemistries of polydopamine coating and LbL assembly provide similar levels of surface modifications. However, there are additional distinct features in polydopamine. First, polydopamine coating is effective for two- or three-dimensional porous materials such as metal-organic frameworks (MOFs), synthetic polyolefin membranes, and others because small-sized dopamine (MW = 153.18 u) and its oxidized oligomers are readily attached onto narrow-spaced surfaces without exhibiting steric hindrance. In contrast, polymers used in LbL assembly are slow in diffusion because of steric hindrance due to their high molecular weight. Second, it is applicable to structurally nonflat surfaces showing special wettability such as superhydrophobicity or superoleophobicity. Third, a nonconducting, insulating polydopamine layer can be converted to be a conducting layer by pyrolysis. The product after pyrolysis is a N-doped graphene-like material that is useful for graphene or carbon nanotube-containing composites. Fourth, it is a suitable method for engineering the surface properties of various composite materials. The surface properties of participating components in composite materials can be unified by polydopamine coating with a simple one-step process. Fifth, a polydopamine layer exhibits intrinsic chemical reactivity by the presence of catecholquinone moieties and catechol radical species on surfaces. Nucleophiles such as amine and thiolate spontaneously react with the functionalized layer. Applications of polydopamine coating are exponentially growing and include cell culture/patterning, microfluidics, antimicrobial surfaces, tissue engineering, drug delivery systems, photothermal therapy, immobilization of photocatalysts, Li-ion battery membranes, Li-sulfur battery cathode materials, oil/water separation, water detoxification, organocatalysts, membrane separation technologies, carbonization, and others. In this Account, we describe various polydopamine coating methods and then introduce a number of chemical derivatives of dopamine that will open further development of material-independent surface chemistry.

Antiadhesive Properties of Oil-Infused Gels against the Universal Adhesiveness of Polydopamine.

Polydopamine (PDA) is well-known as the first material-independent adhesive, which firmly attaches to various substances, even hydrophobic materials, through strong coordinative interactions between the phenolic hydroxyl groups of PDA and the substances. In contrast, oil-infused materials such as self-lubricating gels (SLUGs) exhibit excellent antiadhesive properties against viscous liquids, ice/snow, (bio)fouling, and so on. In this study, we simply questioned: "What will happen when these two materials with contrary nature meet"? To answer this, we formed a PDA layer on a SLUG surface that exhibits thermoresponsive syneretic properties (release of liquid from the gel matrix to the outer surface) and investigated its interfacial behavior. The oil layer caused by syneresis from the SLUGs at -20 °C was found to show resistance to adhesion of universally adhesive PDA.

Phenol-Derived Carbon Sealant Inspired by a Coalification Process.

Recently, emerging functions utilizing phenolic molecules, such as surface functionalizing agents or bioadhesives, have attracted significant interest. However, the most important role of phenolic compounds is to produce carbonized plant matter called "coal", which is widely used as an energy source in nearly all countries. Coalification is a long-term, high-temperature process in which phenols are converted into conducting carbonized matter. This study focuses on mimicking coalification processes to create conducting sealants from non-conducting phenolic compounds by heat treatment. We demonstrate that a phenolic adhesive, tri-hydroxybenzene (known as pyrogallol), and polyethylenimine mixture initially acts as an adhesive sealant that can be converted to a conducting carbon sealing material. The conductivity of the phenolic sealant is about 850 Ω-1 cm-1 , which is an approximately two-fold enhancement of the performance of carbon matter. Applications of the biomimetic adhesives described herein include conducting defect sealants in carbon nanomaterials and conducting binders for metal/carbon or ceramic/carbon composites.

Safety and efficacy evaluations of an adeno-associated virus variant for preparing IL10-secreting human neural stem cell-based therapeutics.

Gene therapy technologies are inevitably required to boost the therapeutic performance of cell therapies; thus, validating the efficacy of gene carriers specifically used for preparing cellular therapeutics is a prerequisite for evaluating the therapeutic capabilities of gene and cell combinatorial therapies. Herein, the efficacy of a recombinant adeno-associated virus derivative (rAAVr3.45) was examined to evaluate its potential as a gene carrier for genetically manipulating interleukin-10 (IL10)-secreting human neural stem cells (hNSCs) that can potentially treat ischemic injuries or neurological disorders. Safety issues that could arise during the virus preparation or viral infection were investigated; no replication-competent AAVs were detected in the final cell suspensions, transgene expression was mostly transient, and no severe interference on endogenous gene expression by viral infection occurred. IL10 secretion from hNSCs infected by rAAVr3.45 encoding IL10 did not alter the transcriptional profile of any gene by more than threefold, but the exogenously boosted IL10 was sufficient to provoke immunomodulatory effects in an ischemic brain injury animal model, thereby accelerating the recovery of neurological deficits and the reduction of brain infarction volume. This study presents evidence that rAAVr3.45 can be potentially used as a gene carrier to prepare stem cell therapeutics.

Tat-Dependent Heterologous Secretion of Recombinant Tyrosinase by Pseudomonas fluorescens Is Aided by a Translationally Fused Caddie Protein.

Tyrosinase is a monooxygenase that catalyzes both the hydroxylation of p-hydroxyphenyl moieties to o-catechols and the oxidation of o-catechols to o-quinones. Apart from its critical functionality in melanogenesis and the synthesis of various neurotransmitters, this enzyme is also used in a variety of biotechnological applications, most notably mediating covalent cross-linking between polymers containing p-hydroxyphenyl groups, forming a hydrogel. Tyrosinases from the genus Streptomyces are usually secreted as a complex with their caddie protein. In this study, we report an increased secretion efficiency observed when the Streptomyces antibioticus tyrosinase gene melC2 was introduced into Pseudomonas fluorescens along with its caddie protein gene melC1, which has the DNA sequence for the Tat (twin-arginine translocation) signal.IMPORTANCE We observed that the S. antibioticus extracellular tyrosinase secretion level was even higher in its nonnatural translationally conjugated fusion protein form than in the natural complex of two separated polypeptides. The results of this study demonstrate that tyrosinase-expressing P. fluorescens can be a stable source of bacterial tyrosinase through exploiting the secretory machinery of P. fluorescens.

Direct Evidence for the Polymeric Nature of Polydopamine.

Inspired by the adhesive proteins of mussels, polydopamine (pDA) has emerged as one of the most widely employed materials for surface functionalization. Despite numerous attempts at characterization, little consensus has emerged regarding whether pDA is a covalent polymer or a noncovalent aggregate of low molecular weight species. Here, we employed single-molecule force spectroscopy (SMFS) to characterize pDA films. Retraction of a pDA-coated cantilever from an oxide surface shows the characteristic features of a polymer with contour lengths of up to 200 nm. pDA polymers are generally weakly bound to the surface through much of their contour length, with occasional "sticky" points. Our findings represent the first direct evidence for the polymeric nature of pDA and provide a foundation upon which to better understand and tailor its physicochemical properties.

Complete prevention of blood loss with self-sealing haemostatic needles.

Bleeding is largely unavoidable following syringe needle puncture of biological tissues and, while inconvenient, this typically causes little or no harm in healthy individuals. However, there are certain circumstances where syringe injections can have more significant side effects, such as uncontrolled bleeding in those with haemophilia, coagulopathy, or the transmission of infectious diseases through contaminated blood. Herein, we present a haemostatic hypodermic needle able to prevent bleeding following tissue puncture. The surface of the needle is coated with partially crosslinked catechol-functionalized chitosan that undergoes a solid-to-gel phase transition in situ to seal punctured tissues. Testing the capabilities of these haemostatic needles, we report complete prevention of blood loss following intravenous and intramuscular injections in animal models, and 100% survival in haemophiliac mice following syringe puncture of the jugular vein. Such self-sealing haemostatic needles and adhesive coatings may therefore help to prevent complications associated with bleeding in more clinical settings.

Dynamic Bonds between Boronic Acid and Alginate: Hydrogels with Stretchable, Self-Healing, Stimuli-Responsive, Remoldable, and Adhesive Properties.

For the increasing demand of soft materials with wide ranges of applications, hydrogels have been developed exhibiting variety of functions (e.g., stretchable, self-healing, stimuli-responsive, and etc.). So far, add-in components such as inorganic nanoparticles, carbon materials, clays, and many others to main polymers have been used to achieve various unique functions of hydrogels. The multicomponent hydrogel systems often exhibit batch-dependent inconsistent results and problems in multicomponent mixings, require labors during preparations, and accompany unpredictable cross-talk between the added components. Here, we developed 'single polymeric component', alginate-boronic acid (alginate-BA) hydrogel to overcome the aforementioned problems. It exhibits unprecedented multifunctionalities simultaneously, such as high stretchability, self-healing, shear-thinning, pH- and glucose-sensitivities, adhesive properties, and reshaping properties. Multifunctionalities of alginate-BA hydrogel is resulted from the reversible inter- and intramolecular interactions by dynamic equilibrium of boronic acid-diol complexation and dissociation, which was proved by single molecule level Atomic Force Microscopy (AFM) pulling experiments. We also found that the alginate-BA gel showed enhanced in vivo retentions along gastrointestinal (GI) tract. Our findings suggest that rational polymer designs can result in minimizing the number of a participating component for multifunctional hydrogels, instead of increasing complexity by adding various additional components.

Microwave-Accelerated Rapid, Chemical Oxidant-Free, Material-Independent Surface Chemistry of Poly(dopamine).

A simple strategy for the rapid preparation of multifunctional polydopamine (pDA) coatings is demonstrated. Microwave irradiation of the coating solution enables the formation of a ≈18 nm thick, genuine pDA coating in 15 min, which is ≈18 times faster than conventional coating. The acceleration effect results from the radical generation and temperature increase, which facilitate thermally accelerated radical polymerization of dopamine.

Precise Targeting of Liver Tumor Using Glycol Chitosan Nanoparticles: Mechanisms, Key Factors, and Their Implications.

Herein, we elucidated the mechanisms and key factors for the tumor-targeting ability of nanoparticles that presented high targeting efficiency for liver tumor. We used several different nanoparticles with sizes of 200-300 nm, including liposome nanoparticles (LNPs), polystyrene nanoparticles (PNPs) and glycol chitosan-5ß-cholanic acid nanoparticles (CNPs). Their sizes are suitable for the enhanced permeation and retention (EPR) effect in literature. Different in vitro characteristics, such as the particle structure, stability, and bioinertness, were carefully analyzed with and without serum proteins. Also, pH-dependent tumor cell uptakes of nanoparticles were studied using fluorescence microscopy. Importantly, CNPs had sufficient stability and bioinertness to maintain their nanoparticle structure in the bloodstream, and they also presented prolonged circulation time in the body (blood circulation half-life T1/2 = about 12.2 h), compared to the control nanoparticles. Finally, employing liver tumor bearing mice, we also observed that CNPs had excellent liver tumor targeting ability in vivo, while LNPs and PNPs demonstrated lower tumor-targeting efficiency due to the nonspecific accumulation in normal liver tissue. Liver tumor models were produced by laparotomy and direct injection of HT29 tumor cells into the left lobe of the liver of athymic nude mice. This study provides valuable information concerning the key factors for the tumor-targeting ability of nanoparticles such as stability, bioinertness, and rapid cellular uptake at targeted tumor tissues.

Astringent Mouthfeel as a Consequence of Lubrication Failure.

Herein, we systematically investigate the origin of astringent mouthfeel when we eat unripe fruits, drink coffee or tea, from the perspective of lubrication by simulating the dynamic weak interaction on the tongue with model protein (mucoprotein, MP) and polyphenolic compounds (tannic acid, TA). Astringency was due to the protein-mediated lubrication failure when encountering polyphenolic molecules that normally exist, for example in unripe fruits, coffee, tea. The underlying molecular mechanism of oral tribology is widely present in nature and enables us to engineer a tongue-like polyacrylamide composite hydrogel that exhibits high TA sensitivity and to develop a scientific strategy for catching slippery fish using TA-containing gloves. These results provide novel and useful insights into the failure of biological boundary lubrication on soft tissue surface with the adsorbed proteins.

Nanomechanics of Poly(catecholamine) Coatings in Aqueous Solutions.

Mussel-inspired self-polymerized catecholamine coatings have been widely utilized as a versatile coating strategy that can be applied to a variety of substrates. For the first time, nanomechanical measurements and an evaluation of the contribution of primary amine groups to poly(catecholamine) coatings have been conducted using a surface-forces apparatus. The adhesive strength between the poly(catecholamine) layers is 30-times higher than that of a poly(catechol) coating. The origin of the strong attraction between the poly(catecholamine) layers is probably due to surface salt displacement by the primary amine, π-π stacking (the quadrupole-quadrupole interaction of indolic crosslinks), and cation-π interactions (the monopole-quadrupole interaction between positively charged amine groups and the indolic crosslinks). The contribution of the primary amine group to the catecholamine coating is vital for the design and development of mussel-inspired catechol-based coating materials.

Painting blood vessels and atherosclerotic plaques with an adhesive drug depot.

The treatment of diseased vasculature remains challenging, in part because of the difficulty in implanting drug-eluting devices without subjecting vessels to damaging mechanical forces. Implanting materials using adhesive forces could overcome this challenge, but materials have previously not been shown to durably adhere to intact endothelium under blood flow. Marine mussels secrete strong underwater adhesives that have been mimicked in synthetic systems. Here we develop a drug-eluting bioadhesive gel that can be locally and durably glued onto the inside surface of blood vessels. In a mouse model of atherosclerosis, inflamed plaques treated with steroid-eluting adhesive gels had reduced macrophage content and developed protective fibrous caps covering the plaque core. Treatment also lowered plasma cytokine levels and biomarkers of inflammation in the plaque. The drug-eluting devices developed here provide a general strategy for implanting therapeutics in the vasculature using adhesive forces and could potentially be used to stabilize rupture-prone plaques.