Near-infrared quantum dots labelled with a tumor selective tetrabranched peptide for in vivo imaging

Simultaneous fingerprinting of multiplex collagen biomarkers in connective tissues by multicolor quantum dots-based peptide probes

The accurate detection of multiplex collagen biomarkers is vital for diagnosing and treating various critical diseases such as tumors and fibrosis. Despite the attractive optical properties of quantum dots (QDs), it remains technically challenging to create stable and specific QDs-based probes for multiplex biological imaging. We report for the first time the construction of multi-color QDs-based peptide probes for the simultaneous fingerprinting of multiplex collagen biomarkers in connective tissues. A bipeptide system composed of a glutathione (GSH) host peptide and a collagen-targeting guest peptide (CTP) has been developed, yielding CTP-QDs probes that exhibit exceptional luminescence stability when exposed to ultraviolet irradiation and mildly acidic conditions. The versatile bipeptide system allows for facile one-pot synthesis of high-quality multicolor CTP-QDs probes, exhibiting superior selectivity in targeting critical collagen biomarkers including denatured collagen, type I collagen, type II collagen, and type IV collagen. The multicolor CTP-QDs probes have demonstrated remarkable efficacy in simultaneously fingerprinting multiple collagen types in diverse connective tissues, irrespective of their status, whether affected by injury, diseases, or undergoing remodeling processes. The innovative multicolor CTP-QDs probes offer a robust toolkit for the multiplex fingerprinting of the collagen suprafamily, demonstrating significant potential in the diagnosis and treatment of collagen-related diseases.

Uptake pathways of cell-penetrating peptides in the context of drug delivery, gene therapy, and vaccine development

Cell-penetrating peptides have been extensively utilized for the purpose of facilitating the intracellular delivery of cargo that is impermeable to the cell membrane. The researchers have exhibited proficient delivery capabilities for oligonucleotides, thereby establishing cell-penetrating peptides as a potent instrument in the field of gene therapy. Furthermore, they have demonstrated a high level of efficiency in delivering several additional payloads. Cell penetrating peptides (CPPs) possess the capability to efficiently transport therapeutic molecules to specific cells, hence offering potential remedies for many illnesses. Hence, their utilization is imperative for the improvement of therapeutic vaccines. In contemporary studies, a plethora of cell-penetrating peptides have been unveiled, each characterized by its own distinct structural attributes and associated mechanisms. Although it is widely acknowledged that there are multiple pathways through which particles might be internalized, a comprehensive understanding of the specific mechanisms by which these particles enter cells has to be fully elucidated. The absorption of cell-penetrating peptides can occur through either direct translocation or endocytosis. However, it is worth noting that categories of cell-penetrating peptides are not commonly linked to specific entrance mechanisms. Furthermore, research has demonstrated that cell-penetrating peptides (CPPs) possess the capacity to enhance antigen uptake by cells and facilitate the traversal of various biological barriers. The primary objective of this work is to examine the mechanisms by which cell-penetrating peptides are internalized by cells and their significance in facilitating the administration of drugs, particularly in the context of gene therapy and vaccine development. The current study investigates the immunostimulatory properties of numerous vaccine components administered using different cell-penetrating peptides (CPPs). This study encompassed a comprehensive discussion on various topics, including the uptake pathways and mechanisms of cell-penetrating peptides (CPPs), the utilization of CPPs as innovative vectors for gene therapy, the role of CPPs in vaccine development, and the potential of CPPs for antigen delivery in the context of vaccine development.

A robust and versatile host-guest peptide toolbox for developing highly stable and specific quantum dot-based peptide probes for imaging extracellular matrices and cells

Multiplex fluorescence imaging plays a vital role in precision medicine for targeting complex diseases with diverse biomolecular signatures. Quantum dot (QD) probes with vibrant colors are promising candidates for multiplex imaging, but their stability and specificity are frequently compromised by the current tedious post-modification process. We have herein developed a robust and versatile host-guest peptide (HGP) toolbox for creating highly stable and specific QD-based peptide probes for imaging extracellular matrices and cells. The HGP system comprises a host peptide and a guest peptide with a shared sequence pattern of cysteine and negatively charged amino acids, allowing for QD stabilization and specificity towards targeted biomarkers. HGP has been demonstrated as a convenient one-step approach to construct hydrophilic QD-based peptide probes with superior stability under various conditions. Six multicolor HGP-modified QDs have been developed to specifically target extracellular matrix proteins such as collagen, laminin, and nidogen, as well as major cellular elements like the membrane, nucleus, and cytoplasm, providing an efficient tool for real-time monitoring of high-resolution interactions between cancer cells and the extracellular matrix. The HGP system represents a next-generation approach to developing QDs with unprecedented stability and specificity, holding great potential in multiplex imaging and precision medicine.

Recent Breakthroughs in Using Quantum Dots for Cancer Imaging and Drug Delivery Purposes

Cancer is one of the leading causes of death worldwide. Because each person's cancer may be unique, diagnosing and treating cancer is challenging. Advances in nanomedicine have made it possible to detect tumors and quickly investigate tumor cells at a cellular level in contrast to prior diagnostic techniques. Quantum dots (QDs) are functional nanoparticles reported to be useful for diagnosis. QDs are semiconducting tiny nanocrystals, 2-10 nm in diameter, with exceptional and useful optoelectronic properties that can be tailored to sensitively report on their environment. This review highlights these exceptional semiconducting QDs and their properties and synthesis methods when used in cancer diagnostics. The conjugation of reporting or binding molecules to the QD surface is discussed. This review summarizes the most recent advances in using QDs for in vitro imaging, in vivo imaging, and targeted drug delivery platforms in cancer applications.

Artificial Photosynthesis: Current Advancements and Future Prospects

Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field.

Targeting Peptides: The New Generation of Targeted Drug Delivery Systems

Peptides can act as targeting molecules, analogously to oligonucleotide aptamers and antibodies. They are particularly efficient in terms of production and stability in physiological environments; in recent years, they have been increasingly studied as targeting agents for several diseases, from tumors to central nervous system disorders, also thanks to the ability of some of them to cross the blood-brain barrier. In this review, we will describe the techniques employed for their experimental and in silico design, as well as their possible applications. We will also discuss advancements in their formulation and chemical modifications that make them even more stable and effective. Finally, we will discuss how their use could effectively help to overcome various physiological problems and improve existing treatments.

Molecular Complementarity of Proteomimetic Materials for Target-Specific Recognition and Recognition-Mediated Complex Functions

As biomolecules essential for sustaining life, proteins are generated from long chains of 20 different α-amino acids that are folded into unique 3D structures. In particular, many proteins have molecular recognition functions owing to their binding pockets, which have complementary shapes, charges, and polarities for specific targets, making these biopolymers unique and highly valuable for biomedical and biocatalytic applications. Based on the understanding of protein structures and microenvironments, molecular complementarity can be exhibited by synthesizable and modifiable materials. This has prompted researchers to explore the proteomimetic potentials of a diverse range of materials, including biologically available peptides and oligonucleotides, synthetic supramolecules, inorganic molecules, and related coordination networks. To fully resemble a protein, proteomimetic materials perform the molecular recognition to mediate complex molecular functions, such as allosteric regulation, signal transduction, enzymatic reactions, and stimuli-responsive motions; this can also expand the landscape of their potential bio-applications. This review focuses on the recognitive aspects of proteomimetic designs derived for individual materials and their conformations. Recent progress provides insights to help guide the development of advanced protein mimicry with material heterogeneity, design modularity, and tailored functionality. The perspectives and challenges of current proteomimetic designs and tools are also discussed in relation to future applications.

Heparan sulfate proteoglycans in cancer: Pathogenesis and therapeutic potential

The heparan sulfate proteoglycans (HSPGs) are glycoproteins that consist of a proteoglycan "core" protein and covalently attached heparan sulfate (HS) chain. HSPGs are ubiquitously expressed in mammalian cells on the cell surface and in the extracellular matrix (ECM) and secretory vesicles. Within HSPGs, the protein cores determine when and where HSPG expression takes place, and the HS chains mediate most of HSPG's biological roles through binding various protein ligands, including cytokines, chemokines, growth factors and receptors, morphogens, proteases, protease inhibitors, and ECM proteins. Through these interactions, HSPGs modulate cell proliferation, adhesion, migration, invasion, and angiogenesis to display essential functions in physiology and pathology. Under physiological conditions, the expression and localization of HSPGs are finely regulated to orchestrate their physiological functions, and this is disrupted in cancer. The HSPG dysregulation elicits multiple oncogenic signaling, including growth factor signaling, ECM and Integrin signaling, chemokine and immune signaling, cancer stem cell, cell differentiation, apoptosis, and senescence, to prompt cell transformation, proliferation, tumor invasion and metastasis, tumor angiogenesis and inflammation, and immunotolerance. These oncogenic roles make HSPGs an attractive pharmacological target for anti-cancer therapy. Several therapeutic strategies have been under development, including anti-HSPG antibodies, peptides and HS mimetics, synthetic xylosides, and heparinase inhibitors, and shown promising anti-cancer efficacy. Therefore, much progress has been made in this line of study. However, it needs to bear in mind that the roles of HSPGs in cancer can be either oncogenic or tumor-suppressive, depending on the HSPG and the cancer cell type with the underlying mechanisms that remain obscure. Further studies need to address these to fill the knowledge gap and rationalize more efficient therapeutic targeting.

The Alterations and Roles of Glycosaminoglycans in Human Diseases

Glycosaminoglycans (GAGs) are a heterogeneous family of linear polysaccharides which are composed of a repeating disaccharide unit. They are also linked to core proteins to form proteoglycans (PGs). GAGs/PGs are major components of the cell surface and the extracellular matrix (ECM), and they display critical roles in development, normal function, and damage response in the body. Some properties (such as expression quantity, molecular weight, and sulfation pattern) of GAGs may be altered under pathological conditions. Due to the close connection between these properties and the function of GAGs/PGs, the alterations are often associated with enormous changes in the physiological/pathological status of cells and organs. Therefore, these GAGs/PGs may serve as marker molecules of disease. This review aimed to investigate the structural alterations and roles of GAGs/PGs in a range of diseases, such as atherosclerosis, cancer, diabetes, neurodegenerative disease, and virus infection. It is hoped to provide a reference for disease diagnosis, monitoring, prognosis, and drug development.

Extracellular matrix-degrading STING nanoagonists for mild NIR-II photothermal-augmented chemodynamic-immunotherapy

Regulation of stimulator of interferon genes (STING) pathway using agonists can boost antitumor immunity for cancer treatment, while the rapid plasma clearance, limited membrane permeability, and inefficient cytosolic transport of STING agonists greatly compromise their therapeutic efficacy. In this study, we describe an extracellular matrix (ECM)-degrading nanoagonist (dNAc) with second near-infrared (NIR-II) light controlled activation of intracellular STING pathway for mild photothermal-augmented chemodynamic-immunotherapy of breast cancer. The dNAc consists of a thermal-responsive liposome inside loading with ferrous sulfide (FeS₂) nanoparticles as both NIR-II photothermal converters and Fenton catalysts, 2′3′-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) as the STING agonist, and an ECM-degrading enzyme (bromelain) on the liposome surface. Mild heat generated by dNAc upon NIR-II photoirradiation improves Fenton reaction efficacy to kill tumor cells and cause immunogenic cell death (ICD). Meanwhile, the generated heat triggers a controlled release of cGAMP from thermal-responsive liposomes to active STING pathway. The mild photothermal activation of STING pathway combined with ICD promotes anti-tumor immune responses, which leads to improved infiltration of effector T cells into tumor tissues after bromelain-mediated ECM degradation. As a result, after treatment with dNAc upon NIR-II photoactivation, both primary and distant tumors in a murine mouse model are inhibited and the liver and lung metastasis are effectively suppressed. This work presents a photoactivatable system for STING pathway and combinational immunotherapy with improved therapeutic outcome.

Real-time cancer diagnosis of breast cancer using fluorescence lifetime endoscopy based on the pH

A biopsy is often performed for the diagnosis of cancer during a surgical operation. In addition, pathological biopsy is required to discriminate the margin between cancer tissues and normal tissues in surgical specimens. In this study, we presented a novel method for discriminating between tumor and normal tissues using fluorescence lifetime endoscopy (FLE). We demonstrated the relationship between the fluorescence lifetime and pH in fluorescein using the proposed fluorescence lifetime measurement system. We also showed that cancer could be diagnosed based on this relationship by assessing differences in pH based fluorescence lifetime between cancer and normal tissues using two different types of tumor such as breast tumors (MDA-MB-361) and skin tumors (A375), where cancer tissues have ranged in pH from 4.5 to 7.0 and normal tissues have ranged in pH from 7.0 to 7.4. To support this approach, we performed hematoxylin and eosin (H&E) staining test of normal and cancer tissues within a certain area. From these results, we showed the ability to diagnose a cancer using FLE technique, which were consistent with the diagnosis of a cancer with H&E staining test. In summary, the proposed pH-based FLE technique could provide a real time, in vivo, and in-situ clinical diagnostic method for the cancer surgical and could be presented as an alternative to biopsy procedures.

Trends in targeted delivery of nanomaterials in colon cancer diagnosis and treatment

Colon cancer is an adenocarcinoma, which subsequently develops into malignant tumors, if not treated properly. The current colon cancer therapy mainly revolves around chemotherapy, radiotherapy and surgery, but the search continues for more effective interventions. With the advancement of nanoparticles (NPs), it is now possible to diagnose and treat colon cancers with different types, shapes, and sizes of NPs. Nanoformulations such as quantum dots, iron oxide, polymeric NPs, dendrimers, polypeptides, gold NPs, silver NPs, platinum NPs, and cerium oxide have been either extensively used alone or in combination with other nanomaterials or drugs in colon cancer diagnosis, and treatments. These nanoformulations possess high biocompatibility and bioavailability, which makes them the most suitable candidates for cancer treatment. The size and shape of NPs are critical to achieving an effective drug delivery in cancer treatment and diagnosis. Most NPs currently are under different testing phases (in vitro, preclinical, and clinical), whereas some of them have been approved for therapeutic applications. We have comprehensively reviewed the recent advances in the applications of NPs-based formulations in colon cancer diagnosis and treatment.

NIR-quantum dots in biomedical imaging and their future

Fluorescence imaging has gathered interest over the recent years for its real-time response and high sensitivity. Developing probes for this modality has proven to be a challenge. Quantum dots (QDs) are colloidal nanoparticles that possess unique optical and electronic properties due to quantum confinement effects, whose excellent optical properties make them ideal for fluorescence imaging of biological systems. By selectively controlling the synthetic methodologies it is possible to obtain QDs that emit in the first (650-950 nm) and second (1000-1400 nm) near infra-red (NIR) windows, allowing for superior imaging properties. Despite the excellent optical properties and biocompatibility shown by some NIR QDs, there are still some challenges to overcome to enable there use in clinical applications. In this review, we discuss the latest advances in the application of NIR QDs in preclinical settings, together with the synthetic approaches and material developments that make NIR QDs promising for future biomedical applications.

Application and Importance of Theranostics in the Diagnosis and Treatment of Cancer

The number of cancer cases worldwide in terms of morbidity and mortality is a serious concern, despite the presence of therapeutic interventions and supportive care. Limitations in the current available diagnosis methods and treatments methods may contribute to the increase in cancer mortality. Theranostics, is a novel approach that has opened avenues for the simultaneous precise diagnosis and treatment for cancer patients. Although still in the early development stage, theranostic agents such as quantum dots, radioisotopes, liposomes and plasmonic nanobubbles can be bound to anticancer drugs, cancer cell markers and imaging agents, with the support of available imaging techniques, provide the potential to facilitate diagnosis, treatment and management of cancer patients. Herein, we discuss the potential benefits of several theranostic tools for the management of cancer. Specifically, quantum dots, radio-labelled isotopes, liposomes and plasmonic nanobubbles coupled with targeting agents and/or anticancer molecules and imaging agents as theranostic agents are deliberated upon in this review. Overall, the use of theranostic agents shows promise in cancer management. Nevertheless, intensive research is required to realize these expectations.

Heparan Sulfate Proteoglycans Can Promote Opposite Effects on Adhesion and Directional Migration of Different Cancer Cells

Heparan sulfate proteoglycans take part in crucial events of cancer progression, such as epithelial-mesenchymal transition, cell migration, and cell invasion. Through sulfated groups on their glycosaminoglycan chains, heparan sulfate proteoglycans interact with growth factors, morphogens, chemokines, and extracellular matrix (ECM) proteins. The amount and position of sulfated groups are highly variable, thus allowing differentiated ligand binding and activity of heparan sulfate proteoglycans. This variability and the lack of specific ligands have delayed comprehension of the molecular basis of heparan sulfate proteoglycan functions. Exploiting a tumor-targeting peptide tool that specifically recognizes sulfated glycosaminoglycans, we analyzed the role of membrane heparan sulfate proteoglycans in the adhesion and migration of cancer cell lines. Starting from the observation that the sulfated glycosaminoglycan-specific peptide exerts a different effect on adhesion, migration, and invasiveness of different cancer cell lines, we identified and characterized three cell migration phenotypes, where different syndecans are associated with alternative signaling for directional cell migration.

Olfactory bulb-targeted quantum dot (QD) bioconjugate and Kv1.3 blocking peptide improve metabolic health in obese male mice

The olfactory system is a driver of feeding behavior, whereby olfactory acuity is modulated by the metabolic state of the individual. The excitability of the major output neurons of the olfactory bulb (OB) can be modulated through targeting a voltage-dependent potassium channel, Kv1.3, which responds to changes in metabolic factors such as insulin, glucose, and glucagon-like peptide-1. Because gene-targeted deletion or inhibition of Kv1.3 in the periphery has been found to increase energy metabolism and decrease body weight, we hypothesized that inhibition of Kv1.3 selectively in the OB could enhance excitability of the output neurons to evoke changes in energy homeostasis. We thereby employed metal-histidine coordination to self-assemble the Kv1.3 inhibitor margatoxin (MgTx) to fluorescent quantum dots (QDMgTx) as a means to label cells in vivo and test changes in neuronal excitability and metabolism when delivered to the OB. Using patch-clamp electrophysiology to measure Kv1.3 properties in heterologously expressed cells and native mitral cells in OB slices, we found that QDMgTx had a fast rate of inhibition, but with a reduced IC_50, and increased action potential firing frequency. QDMgTx was capable of labeling cloned Kv1.3 channels but was not visible when delivered to native Kv1.3 in the OB. Diet-induced obese mice were observed to reduce body weight and clear glucose more quickly following osmotic mini-pump delivery of QDMgTx/MgTx to the OB, and following MgTx delivery, they increased the use of fats as fuels (reduced respiratory exchange ratio). These results suggest that enhanced excitability of bulbar output neurons can drive metabolic responses.

Molecular definition of the interaction between a tumor-specific tetrabranched peptide and LRP6 receptor

The tumor-specific tetrabranched peptide NT4 binds membrane sulfate glycosaminoglycans and receptors belonging to the low density lipoprotein receptor-related protein (LRP) family, like LRP6, which are overexpressed in cancer. The binding occurs through a multimeric positively-charged motif of NT4 that interacts with negatively charged motives in both glycosaminoglycans and LRP receptors. LRP6 has an essential function in canonical Wnt signaling, acting together with receptors of the Frizzled family as coreceptor for Wnt ligands. The extracellular domain of LRP6 contains four YWTD β-propellers, which are fundamental for interactions with ligands, such as Wnt and Wnt inhibitors. To investigate the molecular interactions between the NT4 peptide and LRP6 receptor, we synthesized a library of epitope mapping peptides reproducing the YWTD β-propeller 3 and 4 of LRP6. The peptides that showed to bind NT4 represented the portion of LRP6 located on the top face of β-propeller 3 and contained negatively charged residues, including glutamic acid-708 which is known to be involved in Wnt3a interaction. The results pave the way for a possible development of peptide inhibitors of Wnt3a pathway to be used as drugs in oncology.

Bone Morphogenetic Protein-2 Conjugated to Quantum Dot®s is Biologically Functional

Quantum Dot^®s (QDot^®s) are novel, semi-conductive nanostructures that emit a certain fluorescence when excited by specific wavelengths. QDot^®s are more photostable, brighter, and photobleach less than other fluorescent dyes. These characteristics give them the potential to be used in many biological applications. The shells of QDot^®s are coated with functional groups, such as carboxylate and organic groups, allowing them to couple to peptides/proteins and be used for real-time imaging and high-resolution microscopy. Here, we utilize Quantum Dot^®s and Bone Morphogenetic Protein-2 (BMP-2) to create a BMP-2-QDot^®s conjugate. BMP-2 is a growth factor that drives many processes such as cardiogenesis, neural growth, and osteogenesis. Despite its numerous roles, the trafficking and uptake of BMP-2 into cells is not well-established, especially during progression of diseases. The results presented here demonstrate for the first time a fluorescent BMP-2 analog that binds to the BMP-receptors (BMPRs), remains biologically active, and is stable for long time periods. Previous attempts to develop a biological BMP-2 analog with Fluorescein isothiocyanate (FITC) or nanodiamonds lacked data on the analog’s stability. Furthermore, these analogs did not address whether they can signal within the cell by binding to the BMPRs or were mediated by non-stable conjugates.

Sticking to the Problem: Engineering Adhesion in Molecular Endoscopic Imaging

Cancers of the digestive tract cause nearly one quarter of the cancer deaths worldwide, and nearly half of these are due to cancers of the esophagus and colon. Early detection of cancer significantly increases the rate of survival, and thus it is critical that cancer within these organs is detected early. In this regard, endoscopy is routinely used to screen for transforming/cancerous (i.e. dysplastic to fully cancerous) tissue. Numerous studies have revealed that the biochemistry of the luminal surface of such tissue within the colon and esophagus becomes altered throughout disease progression. Molecular endoscopic imaging (MEI), an emerging technology, seeks to exploit these changes for the early detection of cancer. The general approach for MEI is as follows: the luminal surface of an organ is exposed to molecular ligands, or particulate probes bearing a ligand, cognate to biochemistry unique to pre-cancerous/cancerous tissue. After a wash, the tissue is imaged to determine the presence of the probes. Detection of the probes post-washing suggests pathologic tissue. In the current review we provide a succinct, but extensive, review of ligands and target moieties that could be, or are currently being investigated, as possible cognate chemistries for MEI. This is followed by a review of the biophysics that determines, in large part, the success of a particular MEI design. The work draws an analogy between MEI and the well-advanced field of cell adhesion and provides a road map for engineering MEI to achieve assays that yield highly selective recognition of transforming/cancerous tissue in situ.

Cell Penetrating Peptides, Novel Vectors for Gene Therapy

Cell penetrating peptides (CPPs), also known as protein transduction domains (PTDs), first identified ~25 years ago, are small, 6-30 amino acid long, synthetic, or naturally occurring peptides, able to carry variety of cargoes across the cellular membranes in an intact, functional form. Since their initial description and characterization, the field of cell penetrating peptides as vectors has exploded. The cargoes they can deliver range from other small peptides, full-length proteins, nucleic acids including RNA and DNA, liposomes, nanoparticles, and viral particles as well as radioisotopes and other fluorescent probes for imaging purposes. In this review, we will focus briefly on their history, classification system, and mechanism of transduction followed by a summary of the existing literature on use of CPPs as gene delivery vectors either in the form of modified viruses, plasmid DNA, small interfering RNA, oligonucleotides, full-length genes, DNA origami or peptide nucleic acids.

A New NT4 Peptide-Based Drug Delivery System for Cancer Treatment

The development of selective tumor targeting agents to deliver multiple units of chemotherapy drugs to cancer tissue would improve treatment efficacy and greatly advance progress in cancer therapy. Here we report a new drug delivery system based on a tetrabranched peptide known as NT4, which is a promising cancer theranostic by virtue of its high cancer selectivity. We developed NT4 directly conjugated with one, two, or three units of paclitaxel and an NT4-based nanosystem, using NIR-emitting quantum dots, loaded with the NT4 tumor-targeting agent and conjugated with paclitaxel, to obtain a NT4-QD-PTX nanodevice designed to simultaneously detect and kill tumor cells. The selective binding and in vitro cytotoxicity of NT4-QD-PTX were higher than for unlabeled QD-PTX when tested on the human colon adenocarcinoma cell line HT-29. NT4-QD-PTX tumor-targeted nanoparticles can be considered promising for early tumor detection and for the development of effective treatments combining simultaneous therapy and diagnosis.

Unraveling Heparan Sulfate Proteoglycan Binding Motif for Cancer Cell Selectivity

Membrane heparan sulfate proteoglycans (HSPG) regulate cell proliferation, migration, and differentiation and are therefore considered key players in cancer cell development processes. Here, we used the NT4 peptide to investigate how the sulfation pattern of HSPG on cells drives binding specificity. NT4 is a branched peptide that binds the glycosaminoglycan (GAG) chains of HSPG. It has already been shown to inhibit growth factor-induced migration and invasiveness of cancer cells, implying antagonist binding of HSPG. The binding affinity of NT4 with recombinant HSPG showed that NT4 bound glypican-3 and -4 and, with lower affinity, syndecan-4. NT4 binding to the cancer cell membrane was inversely correlated with sulfatase expression. NT4 binding was higher in cell lines with lower expression of SULF-1 and SULF-2, which confirms the determinant role of sulfate groups for recognition by NT4. Using 8-mer and 9-mer heparan sulfate (HS) oligosaccharides with analog disaccharide composition and different sulfation sites, a possible recognition motif was identified that includes repeated 6-O-sulfates alternating with N- and/or 2-O-sulfates. Molecular modeling provided a fully descriptive picture of binding architecture, showing that sulfate groups on opposite sides of the oligosaccharide can interact with positive residues on two peptide sequences of the branched structure, thus favoring multivalent binding and explaining the high affinity and selectivity of NT4 for highly sulfated GAGs. NT4 and possibly newly selected branched peptides will be essential probes for reconstructing and unraveling binding sites for cancer-involved ligands on GAGs and will pave the way for new cancer detection and treatment options.