Enantioselective Detection of Gaseous Odorants with Peptide-Graphene Sensors Operating in Humid Environments.

Replicating the sense of smell presents an ongoing challenge in the development of biomimetic devices. Olfactory receptors exhibit remarkable discriminatory abilities, including the enantioselective detection of individual odorant molecules. Graphene has emerged as a promising material for biomimetic electronic devices due to its unique electrical properties and exceptional sensitivity. However, the efficient detection of nonpolar odor molecules using transistor-based graphene sensors in a gas phase in environmental conditions remains challenging due to high sensitivity to water vapor. This limitation has impeded the practical development of gas-phase graphene odor sensors capable of selective detection, particularly in humid environments. In this study, we address this challenge by introducing peptide-functionalized graphene sensors that effectively mitigate undesired responses to changes in humidity. Additionally, we demonstrate the significant role of humidity in facilitating the selective detection of odorant molecules by the peptides. These peptides, designed to mimic a fruit fly olfactory receptor, spontaneously assemble into a monomolecular layer on graphene, enabling precise and specific odorant detection. The developed sensors exhibit notable enantioselectivity, achieving a remarkable 35-fold signal contrast between d- and l-limonene. Furthermore, these sensors display distinct responses to various other biogenic volatile organic compounds, demonstrating their versatility as robust tools for odor detection. By acting as both a bioprobe and an electrical signal amplifier, the peptide layer represents a novel and effective strategy to achieve selective odorant detection under normal atmospheric conditions using graphene sensors. This study offers valuable insights into the development of practical odor-sensing technologies with potential applications in diverse fields.

Osmotic stress induces the formation of migrasome-like vesicles.

Migrasomes are extracellular vesicles that form on the retraction fibers of migrating cells. In this study, we report the formation of migrasome-like vesicles enriched in tetraspanin 4 and containing cytoplasmic components in response to hypoosmotic stress. When migrating cells were subjected to hypoosmotic stress, vesicles with a size distribution of 0.5 to 2 µm formed on the retraction fibers, and vanished in a few minutes. The vesicles are rich in cholesterol, and their number was reduced when cells were pretreated with lipoprotein-deficient serum. The formation of migrasome-like vesicles upon hypoosmotic stress may provide biophysical cues regarding the cellular response to this external stimulus in cells and tissues.

Screening of novel DPP-IV inhibitory peptides derived from bovine milk proteins using a peptide array platform.

Dipeptidyl peptidase IV (DPP-IV) has become an important target in the prevention and treatment of diabetes. Although many DPP-IV inhibitory peptides have been identified by a general approach involving the repeated fractionation of food protein hydrolysates, the obtained results have been dependent on the content of each peptide and fractionation conditions. In the present study, a peptide array that provides comprehensive assays of peptide sequences was used to identify novel DPP-IV inhibitory peptides derived from bovine milk proteins; these peptides were then compared with those identified using the general approach. While the general approach identified only known peptides that were abundant in the hydrolysate, the peptide array-based approach identified 10 novel DPP-IV inhibitory peptides, all of which had proline at the second residue from the N-terminus. The proper or combined use of these two approaches, which have different advantages, will enable the efficient development of novel bioactive foods and drugs.

O-GlcNAcylation is essential for therapeutic mitochondrial transplantation.

BACKGROUND: Transplantation of mitochondria is increasingly explored as a novel therapy in central nervous system (CNS) injury and disease. However, there are limitations in safety and efficacy because mitochondria are vulnerable in extracellular environments and damaged mitochondria can induce unfavorable danger signals. METHODS: Mitochondrial O-GlcNAc-modification was amplified by recombinant O-GlcNAc transferase (OGT) and UDP-GlcNAc. O-GlcNAcylated mitochondrial proteins were identified by mass spectrometry and the antiglycation ability of O-GlcNAcylated DJ1 was determined by loss-of-function via mutagenesis. Therapeutic efficacy of O-GlcNAcylated mitochondria was assessed in a mouse model of transient focal cerebral ischemia-reperfusion. To explore translational potential, we evaluated O-GlcNAcylated DJ1 in CSF collected from patients with subarachnoid hemorrhagic stroke (SAH). RESULTS: We show that isolated mitochondria are susceptible to advanced glycation end product (AGE) modification, and these glycated mitochondria induce the receptor for advanced glycation end product (RAGE)-mediated autophagy and oxidative stress when transferred into neurons. However, modifying mitochondria with O-GlcNAcylation counteracts glycation, diminishes RAGE-mediated effects, and improves viability of mitochondria recipient neurons. In a mouse model of stroke, treatment with extracellular mitochondria modified by O-GlcNAcylation reduces neuronal injury and improves neurologic deficits. In cerebrospinal fluid (CSF) samples from SAH patients, levels of O-GlcNAcylation in extracellular mitochondria correlate with better clinical outcomes. CONCLUSIONS: These findings suggest that AGE-modification in extracellular mitochondria may induce danger signals, but O-GlcNAcylation can prevent glycation and improve the therapeutic efficacy of transplanted mitochondria in the CNS.

Mitochondria are the part of a cell that generate most of its energy to perform its functions. In injury or disease, mitochondrial function can become disrupted. Transplantation of healthy mitochondria is being explored as a potential therapy to replace damaged mitochondria and restore normal cellular function. However, this approach is difficult to perform because mitochondria are not able to maintain their healthy state outside of cells. Here, we show that one of the reasons for this is due to a molecular process called advanced glycation end product modification. We show that simple modification of mitochondria with a sugar prevents this process and helps to improve the success of therapeutic mitochondrial transplantation in cells and in a mouse model of stroke. Our findings may help to guide future efforts to develop therapies based on mitochondrial transplantation.

Antibacterial and biofilm-inhibiting cotton fabrics decorated with copper nanoparticles grown on graphene nanosheets.

Infectious pathogens can be transmitted through textiles. Therefore, additional efforts are needed to develop functional fabrics containing antimicrobial substances to prevent the growth of antibiotic-resistant bacteria and their biofilms. Here, we developed a cotton fabric coated with reduced graphene oxide (rGO) and copper nanoparticles (Cu NPs), which possessed hydrophobic, antimicrobial, and anti-biofilm properties. Once the graphene oxide was dip-coated on a cellulose cotton fabric, Cu NPs were synthesized using a chemical reduction method to fabricate an rGO/Cu fabric, which was analyzed through FE-SEM, EDS, and ICP-MS. The results of our colony-forming unit assays indicated that the rGO/Cu fabric possessed high antibacterial and anti-biofilm properties against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Corynebacterium xerosis, and Micrococcus luteus. Particularly, the fabric could inhibit the growth of E. coli, C. xerosis, and M. luteus with a 99% efficiency. Furthermore, our findings confirmed that the same concentrations of rGO/Cu had no cytotoxic effects against CCD-986Sk and Human Dermal Fibroblast (HDF), human skin cells, and NIH/3T3, a mouse skin cell. The developed rGO/Cu fabric thus exhibited promising applicability as a cotton material that can maintain hygienic conditions by preventing the propagation of various bacteria and sufficiently suppressing biofilm formation while also being harmless to the human body.

Detection of CpG methylation level using methyl-CpG-binding domain-fused fluorescent protein.

Methylation of cytosine to 5-methylcytosine on CpG dinucleotides is the most frequently studied epigenetic modification involved in the regulation of gene expression. In normal tissues, tissue-specific CpG methylation patterns are established during development. In contrast, alterations in methylation patterns have been observed in abnormal cells, such as cancer cells. Cancer type-specific CpG methylation patterns have been identified and used as biomarkers for cancer diagnosis. In this study, we developed a hybridization-based CpG methylation level sensing system using a methyl-CpG-binding domain (MBD)-fused fluorescent protein. In this system, the target DNA is captured by a complementary methylated probe DNA. When the target DNA is methylated, a symmetrically methylated CpG is formed in the double-stranded DNA. MBD specifically recognizes symmetrical methyl-CpG on double-stranded DNA; therefore, the methylation level is quantified by measuring the fluorescence intensity of the bound MBD-fused fluorescent protein. We prepared MBD-fused AcGFP1 and quantified the CpG methylation levels of the target DNA against SEPT9, BRCA1, and long interspersed nuclear element-1 (LINE-1) using MBD-AcGFP1. This detection principle can be applied to the simultaneous and genome-wide modified base detection systems using microarrays coupled with modified base binding proteins fused to fluorescent proteins.

Lipid-based colloidal nanoparticles for applications in targeted vaccine delivery.

Bioactive molecules and their effects have been influenced by their solubility and administration route. In many therapeutic reagents, the performance of therapeutics is dependent on physiological barriers in the human body and delivery efficacy. Therefore, an effective and stable therapeutic delivery promotes pharmaceutical advancement and suitable biological usage of drugs. In the biological and pharmacological industries, lipid nanoparticles (LNPs) have emerged as a potential carrier to deliver therapeutics. Since studies reported doxorubicin-loaded liposomes (Doxil®), LNPs have been applied to numerous clinical trials. Lipid-based nanoparticles, including liposomes, solid lipid nanoparticles (SLNs), and nanostructured lipid nanoparticles, have also been developed to deliver active ingredients in vaccines. In this review, we present the type of LNPs used to develop vaccines with attractive advantages. We then discuss messenger RNA (mRNA) delivery for the clinical application of mRNA therapeutic-loaded LNPs and recent research trend of LNP-based vaccine development.

Screening of EWI-2-Derived Peptides for Targeting Tetraspanin CD81 and Their Effect on Cancer Cell Migration.

CD81, a transmembrane protein belonging to the tetraspanin family, has recently been suggested as a therapeutic target for cancers. Here, we screened peptides that bind to the tetraspanin CD81 protein, and evaluated their inhibitory activity in cancer cell migration. To screen for CD81-binding peptides (CD81-BP), a peptide array membrane was prepared from the amino acid sequence of the EWI-2 protein, a major partner of CD81, before binding to fluorescently labeled CD81. As a result, four candidate CD81-BPs were identified and characterized. In particular, the CFMKRLRK peptide (called P152 in this study) was found to be the best candidate that preferentially binds to the extracellular loop of CD81, with an estimated dissociation constant of 0.91 µM. Since CD81 was reported to promote cancer cell migration, an initial step in metastasis, the Boyden chamber assay, was next performed to assess the effect of CD81-BP candidates on the migration of MDA-MB-231 human breast cancer cells. Interestingly, our result indicated that P152 could suppress MDA-MB-231 cell migration at the level comparable to that of an anti-human CD81 antibody (5A6). Thus, we propose these CD81-BPs with the anti-migration property against cancer cells for the development of novel therapeutic strategies.

Volatile Organic Compound Detection by Graphene Field-Effect Transistors Functionalized with Fly Olfactory Receptor Mimetic Peptides.

An olfactory receptor mimetic peptide-modified graphene field-effect transistor (gFET) is a promising solution to overcome the principal challenge of low specificity graphene-based sensors for volatile organic compound (VOC) sensing. Herein, peptides mimicking a fruit fly olfactory receptor, OR19a, were designed by a high-throughput analysis method that combines a peptide array and gas chromatography for the sensitive and selective gFET detection of the signature citrus VOC, limonene. The peptide probe was bifunctionalized via linkage of a graphene-binding peptide to facilitate one-step self-assembly on the sensor surface. The limonene-specific peptide probe successfully achieved highly sensitive and selective detection of limonene by gFET, with a detection range of 8-1000 pM, while achieving facile sensor functionalization. Taken together, our target-specific peptide selection and functionalization strategy of a gFET sensor demonstrates advancement of a precise VOC detection system.

A peptide binding to the tetraspanin CD9 reduces cancer metastasis.

As an organizer of multi-molecular membrane complexes, the tetraspanin CD9 has been implicated in a number of biological processes, including cancer metastasis, and is a candidate therapeutic target. Here, we evaluated the suppressive effects of an eight-mer CD9-binding peptide (CD9-BP) on cancer cell metastasis and its mechanisms of action. CD9-BP impaired CD9-related functions by adversely affecting the formation of tetraspanin webs-networks composed of CD9 and its partner proteins. The anti-cancer metastasis effect of CD9-BP was evidenced by the in vitro inhibition of cancer cell migration and invasion as well as exosome secretion and uptake, which are essential processes during metastasis. Finally, using a mouse model, we showed that CD9-BP reduced lung metastasis in vivo. These findings provide insight into the mechanism by which CD9-BP inhibits CD9-dependent functions and highlight its potential application as an alternative therapeutic nano-biomaterial for metastatic cancers.

Physiological significance of elevated levels of lactate by exercise training in the brain and body.

For the past 200 years, lactate has been regarded as a metabolic waste end product that causes fatigue during exercise. However, lactate production is closely correlated with energy metabolism. The lactate dehydrogenase-catalyzed reaction uses protons to produce lactate, which delays ongoing metabolic acidosis. Of note, lactate production differs depending on exercise intensity and is not limited to muscles. Importantly, controlling physiological effect of lactate may be a solution to alleviating some chronic diseases. Released through exercise, lactate is an important biomarker for fat oxidation in skeletal muscles. During recovery after sustained strenuous exercise, most of the lactate accumulated during exercise is removed by direct oxidation. However, as the muscle respiration rate decreases, lactate becomes a desirable substrate for hepatic glucose synthesis. Furthermore, improvement in brain function by lactate, particularly, through the expression of vascular endothelial growth factor and brain-derived neurotrophic factor, is being increasingly studied. In addition, it is possible to improve stress-related symptoms, such as depression, by regulating the function of hippocampal mitochondria, and with an increasingly aging society, lactate is being investigated as a preventive agent for brain diseases such as Alzheimer's disease. Therefore, the perception that lactate is equivalent to fatigue should no longer exist. This review focuses on the new perception of lactate and how lactate acts extensively in the skeletal muscles, heart, brain, kidney, and liver. Additionally, lactate is now used to confirm exercise performance and should be further studied to assess its impact on exercise training.

Designable peptides on graphene field-effect transistors for selective detection of odor molecules.

Gas sensing based on graphene field-effect transistors (GFETs) has gained broad interest due to their high sensitivity. Further progress in gas sensing with GFETs requires to detection of various odor molecules for applications in the environmental monitoring, healthcare, food, and cosmetic industries. To develop the ubiquitous odor-sensing system, establishing an artificial sense of smell with electronic devices by mimicking olfactory receptors will be key. Although the application of olfactory receptors to GFETs is straightforward for odor sensing, synthetic molecules with a similar function to olfactory receptors would be desirable to realize the robust performance of sensing. In this work, we designed three new peptides consisting of two domains: a bio-probe to the target molecules and a molecular scaffold. These peptides were rationally designed based on a motif sequence in olfactory receptors and self-assembled into a molecular thin film on GFETs. Limonene, methyl salicylate, and menthol were employed as representative odor molecules of plant flavors to demonstrate the biosensing of odor molecules. The conductivity change of GFETs against the binding to odor molecules with various concentrations and the dynamic response revealed a distinct signature of three different peptides against individual species of the target molecules. The kinetic response of each peptide exhibited characteristic time constants in the adsorption and desorption process, also supported by the principal component analysis. Our demonstration of the graphene odor sensors with the designed peptides opens a way to establish future peptide-array sensors with multi-sequence of peptide, realizing an odor sensing system with higher selectivity.

Endothelial cells regulate astrocyte to neural progenitor cell trans-differentiation in a mouse model of stroke.

The concept of the neurovascular unit emphasizes the importance of cell-cell signaling between neural, glial, and vascular compartments. In neurogenesis, for example, brain endothelial cells play a key role by supplying trophic support to neural progenitors. Here, we describe a surprising phenomenon where brain endothelial cells may release trans-differentiation signals that convert astrocytes into neural progenitor cells in male mice after stroke. After oxygen-glucose deprivation, brain endothelial cells release microvesicles containing pro-neural factor Ascl1 that enter into astrocytes to induce their trans-differentiation into neural progenitors. In mouse models of focal cerebral ischemia, Ascl1 is upregulated in endothelium prior to astrocytic conversion into neural progenitor cells. Injecting brain endothelial-derived microvesicles amplifies the process of astrocyte trans-differentiation. Endothelial-specific overexpression of Ascl1 increases the local conversion of astrocytes into neural progenitors and improves behavioral recovery. Our findings describe an unexpected vascular-regulated mechanism of neuroplasticity that may open up therapeutic opportunities for improving outcomes after stroke.

Mitochondrial surface coating with artificial lipid membrane improves the transfer efficacy.

Extracellular mitochondria are present and act as non-cell-autonomous signals to support energetic homeostasis. While mitochondria allograft is a promising approach in rescuing neurons, glia, and vascular cells in CNS injury and disease, there are profound limitations in cellular uptake of mitochondria together with the efficacy. Here, we modified mitochondria by coating them with cationic DOTAP mixed with DOPE via a modified inverted emulsion method to improve mitochondrial transfer and efficacy. We initially optimized the method using control microbeads and liposomes followed by using mitochondria isolated from intact cerebral cortex of male adult C57BL/6J mice. After the coating process, FACS analysis indicated that approximately 86% of mitochondria were covered by DOTAP/DOPE membrane. Moreover, the artificial membrane-coated mitochondria (AM-mito) shifted the zeta-potential toward positive surface charge, confirming successful coating of isolated mitochondria. Mitochondrial proteins (TOM40, ATP5a, ACADM, HSP60, COX IV) and membrane potentials were well maintained in AM-mito. Importantly, the coating improved mitochondrial internalization and neuroprotection in cultured neurons. Furthermore, intravenous infusion of AM-mito immediately after focal cerebral ischemia-reperfusion amplified cerebroprotection in vivo. Collectively, these findings indicate that mitochondrial surface coating with artificial lipid membrane is feasible and may improve the therapeutic efficacy of mitochondria allograft.

Sensitive and specific capture of polystyrene and polypropylene microplastics using engineered peptide biosensors.

Owing to increased environmental pollution, active research regarding microplastics circulating in the ocean has attracted significant interest in recent times. Microplastics accumulate in the bodies of living organisms and adversely affect them. In this study, a new method for the rapid detection of microplastics using peptides was proposed. Among the various types of plastics distributed in the ocean, polystyrene and polypropylene were selected. The binding affinity of the hydrophobic peptides suitable for each type of plastic was evaluated. The binding affinities of peptides were confirmed in unoxidized plastics and plasma-oxidized plastics in deionised or 3.5% saline water. Also, the detection of microplastics in small animals' intestine extracts were possible with the reported peptide biosensors. We expect plastic-binding peptides to be used in sensors to increase the detection efficiency of microplastics and potentially help separate microplastics from seawater.

Surface glycan targeting for cancer nano-immunotherapy.

Cancer immunotherapy is an emerging therapeutic strategy for cancer treatment. Most of the immunotherapeutics approved by the FDA regulate the innate immune system and associated immune cell activity, with immune check inhibitors in particular having transformed the field of cancer immunotherapy due to their significant clinical potential. However, previously reported immunotherapeutics have exhibited undesirable side effects, including autoimmune toxicity and inflammation. Controlling these deleterious responses and designing therapeutics that can precisely target specific regions are thus crucial to improving the efficacy of cancer immunotherapies. Recent studies have reported that cancer cells employ glycan-immune checkpoint interactions to modulate immune cell activity. Thus, the recognition of cancer glycan moieties such as sialoglycans may improve the anticancer activity of immune cells. In this review, we discuss recent advances in cancer immunotherapies involving glycans and glycan-targeting technologies based on nanomaterial-assisted local delivery systems.

Enrichment of membrane curvature-sensing proteins from Escherichia coli using spherical supported lipid bilayers.

Bacteria display dynamically organized curved membrane structures, especially during cell division. The importance of membrane curvature-sensing (MCS) proteins for the recognition and regulation of biological membrane morphologies has predominately been investigated in eukaryotic cells. Recently, a technique for screening MCS proteins from solutions that contain peripheral membrane proteins was developed, and MCS protein candidates were identified from mammalian cells. The technique uses differently sized spherical supported lipid bilayers (SSLBs), which consist of spherical SiO2 particles covered with a lipid bilayer. To discriminate between proteins possessing the MCS property, SSLBs with the same surface area were used in a comparative sedimentation assay with shotgun proteome analysis. In this study, to prove that the technique could be applied to other samples, MCS proteins in Escherichia coli were investigated. Through a comparative proteomic study, 35 and 47 proteins were enriched as candidate MCS proteins preferentially bound to SSLBs of 100 nm and 1000 nm, respectively. Among the identified MCS candidate proteins, FtsZ and SecA were further examined for their MCS properties using the two SSLB sizes, which revealed a high binding affinity for the low membrane curvature (large SSLB). This is the first study to explore MCS proteins in prokaryotic cells and the MCS property of the SecA protein. The results demonstrate a method to enrich MCS proteins that could be utilized to better elucidate membrane dynamics and protein function expression on curved membrane structures in prokaryotic cells.

Peptide-modified substrate enhances cell migration and migrasome formation.

Extracellular vesicles (EVs) are cell-to-cell communication tools. Migrasomes are recently discovered microscale EVs formed at the rear ends of migrating cells, and thus are suggested to be involved in communicating with neighboring cells. In cell culture, peptide scaffolds on substrates have been used to demonstrate cellular function for regenerative medicine. In this study, we evaluated peptide scaffolds, including cell penetrating, virus fusion, and integrin-binding peptides, for their potential to enable the formation of migrasome-like vesicles. Through structural and functional analyses, we confirmed that the EVs formed on these peptide-modified substrates were migrasomes. We further noted that the peptide interface comprising cell-penetrating peptides (pVEC and R9) and virus fusion peptide (SIV) have superior properties for enabling cell migration and migrasome formation than fibronectin protein, integrin-binding peptide (RGD), or bare substrate. This is the first report of migrasome formation on peptide-modified substrates. Additionally, the combination of 95% RGD and 5% pVEC peptides provided a functional interface for effective migrasome formation and desorption of cells from the substrate via a simple ethylenediaminetetraacetic acid treatment. These results provide a functional substrate for the enhancement of migrasome formation and functional analysis.

Oxygen transport to mammalian cell and bacteria using nano-sized liposomes encapsulating oxygen molecules.

Hypoxic microenvironments emerge as tumor grow, leading to the over-expression and stabilization of hypoxia-inducible factor 1-alpha (HIF-1α). HIF-1α lowers the sensitization against chemotherapy, radiation therapy and photodynamic therapy in cancer. In this study, nano-sized oxygen carrier, namely oxygen dissolved nanoliposome (ODL) was synthesized, and oxygen was efficiently delivered to different types of mammalian cells to help relieve hypoxia. ODL confirmed that oxygen was released without inducing toxicity to cells. After artificially creating hypoxia in cancer cells, normal cells, and immune cells; various parameters such as cell morphology, HIF-1α expression, and degree of hypoxia were examined. The cellular environment was found to be altered by treatment with the ODL. Under hypoxia, the shape of the cells changed, and the cells began to die. After treatment with the ODL, the degree of hypoxia was reduced, indicating that HIF-1α expression and the rate of cell death decreased. Furthermore, bacteria proliferation was observed with the ODL. Therefore, ODL can be used for oxygen delivery platform in cancer therapy. ODL has a potential application in other microorganisms which needs future research.

Inhalable nanoparticles delivery targeting alveolar macrophages for the treatment of pulmonary tuberculosis.

Pulmonary tuberculosis is a highly prevalent respiratory disease that affects approximately a quarter of the world's population. The drug treatment protocol for tuberculosis is complex because the Mycobacterium tuberculosis (M. tuberculosis) invades macrophages and begins to infect. Thus treatment usually includes combination therapy with several drugs such as rifampicin, pyrazinamide, isoniazid, and ethambutol over a long dosing period. Therefore, drug-delivery technologies have been developed to improve patient compliance with medication, reduce adverse effects, and increase effectiveness of the treatment. In the present review, we have discussed recent inhalable nanopharmaceutical systems for the treatment of pulmonary tuberculosis and investigated their design and effectiveness. We examined the underlying processes and characteristics of spray-drying technology and studied the formulation of a dry carrier using spray-drying method. Moreover, we reviewed various research articles on pulmonary delivery of nanoparticles using these carriers, and studied their alveolar macrophage targeting ability and therapeutic effects. Further, we appraised the effectiveness of nanoparticle inhalation therapy for the treatment of pulmonary tuberculosis and its potential as a treatment strategy for lung diseases.