Low Nonspecific Interactions Research Articles

Bioconjugated Nanomaterial for Targeted Diagnosis of SARS-CoV-2.

ConspectusInfectious diseases by pathogenic microorganisms are one of the leading causes of mortality worldwide. Healthcare and socio-economic development have been seriously affected for different civilizations because of bacterial and viral infections. According to the Centers for Disease Control and Prevention (CDC), pandemic in 1918 by the Influenza A virus of the H1N1 subtype was responsible for 50 to 100 million deaths worldwide. Similarly, the Asian flu pandemic in 1957, Hong Kong flu in 1968, and H1N1pdm09 flu pandemic in 2009 were responsible for more than 1 million deaths across the globe each time. As per the World Health Organization (WHO), the current pandemic by coronavirus disease 2019 (COVID-19) due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is responsible for more than 4.8 M death worldwide until now. Since the gold standard polymerase chain reaction (PCR) test is more time-consuming, the health care system cannot test all symptomatic and asymptomatic Covid patients every day, which is extremely important to tackle the outbreak. One of the significant challenges during the current pandemic is developing mass testing tools, which is critical to control the virus spread in the community. Therefore, it is highly desirable to develop advanced material-based approaches that can provide a rapid and accurate diagnosis of COVID-19, which will have the capability to save millions of human lives.Aiming for the targeted diagnosis of deadly virus, researchers have developed nanomaterials with various sizes, shapes, and dimensions. These nanomaterials have been used to identify biomolecules via unique optical, electrical, magnetic, structural, and functional properties, which are lacking in other materials. Despite significant progress, nanomaterial-based diagnosis of biomolecules is still facing several obstacles due to low targeting efficiency and nonspecific interactions. To overcome these problems, the bioconjugated nanoparticle has been designed via surface coating with polyethylene glycol (PEG) and then conjugated with antibodies, DNA, RNA, or peptide aptamers. Therefore, the current Account summarizes an overview of the recent advances in the design of bioconjugated nanomaterial-based approached as effective diagnosis of the SARS-CoV-2 virus and the SARS-CoV-2 viral RNA, antigen, or antibody, with a particular focus on our work and other’s work related to this subject. First, we present how to tailor the surface functionalities of nanomaterials to achieve bioconjugated material for targeted diagnosis of the virus. Then we review the very recent advances in the design of antibody/aptamer/peptide conjugated nanostructure, which represent a powerful platform for naked-eye colorimetric detection via plasmonic nanoparticles. We then discuss nanomaterial-based surface-enhanced Raman scattering (SERS) spectroscopy, which has the capability for very low-level fingerprint identification of virus, antigen, and antibody via graphene, plasmonic nanoparticle, and heterostructure material. After that, we summarized about fluorescence and nanoparticle surface energy transfer (NSET)-based on specific identification of SARS-CoV-2 infections via CNT, quantum dots (QDs), and plasmonic nanoparticles. Finally, we highlight the merit and significant challenges of nanostructure-based tools in infectious diseases diagnosis. For the researchers who want to engage in the new development of bioconjugated material for our survival from the current and future pandemics, we hope that this Account will be helpful for generating ideas that are scientifically stimulating and practically challenging.

In Silico Based Approach to Investigate Plant Lignans as Inhibitor Candidates for Estrogen Receptor in Breast Cancer

Background: In the last decades, growing evidence demonstrates interest in phytoestrogen intake to modulate targets in different types of cancer. Plant lignans have proven efficacious in blocking estrogen receptors of breast cancer cells. Among them, four phytoestrogen lignans: pinoresinol, matairesinol, lariciresinol, and secoisolariciresinol have been most studied. However, available studies have mostly dealt with the anti-cancer effects of groups of lignans in certain foods or plants and the effects of specific lignans, especially from a molecular interaction viewpoint, have been rarely addressed in the literature. Objective: We aimed to in silico predict pharmacological properties, binding ability and binding strength of pinoresinol, matairesinol, lariciresinol and secoisolariciresinol as possible inhibitors of estrogen receptor alpha which is the most important biomarker in breast cancer. Methods: Firstly, we evaluated the pharmacological properties of four lignans using SwissADME. Then we investigated the ligand-receptor interactions of these molecules as positively appraised ligands for ER-positive breast cancer targeted therapy using docking method. We finally compared the inhibitory effect possibility of the lignans against endoxifen which is the active metabolite of tamoxifen. Results: The best binding affinity of endoxifen, matairesinol, pinoresinol, lariciresinol and secoisolariciresinol were respectively -9.2, -7.5, -6.7, -6.7, -5.8 kcal/mol. In the meantime, matairesinol showed a minimum binding energy than other studied lignans in addition to the most similar interactions to endoxifen with conserved domain residues of the active site pocket in Leu:391, Ala:350, Met:421, and Phe:404. Conclusion: Among the studied lignans, matairesinol showed favorable pharmacokinetics and drug-likeliness properties, the least binding energy as well as the most common interactions in conserved residues of the active site pocket with estrogens. This makes it a molecule with low number of nonspecific interactions, better target selectivity, and hence fewer side effects. Thus, our results introduce matairesinol as a possibly effective anti-estrogen receptor inhibitor candidate.

An Ultrastable and Dense Single-Molecule Click Platform for Sensing Protein-Deoxyribonucleic Acid Interactions.

An ultrastable, highly dense single-molecule assay ideal for observing protein-DNA interactions is demonstrated. Stable click tethered particle motion leverages next generation click-chemistry to achieve an ultrahigh density of surface tethered reporter particles, and has low non-specific interactions, is stable at elevated temperatures to at least 45°C, and is compatible with Mg2+ , an important ionic component of many regulatory protein-DNA interactions. Prepared samples remain stable, with little degradation, for >6 months in physiological buffers. These improvements enable the authors to study previously inaccessible sequence and temperature-dependent effects on DNA binding by the bacterial protein, histone-like nucleoid-structuring protein, a global transcriptional regulator found in Escherichia coli. This greatly improved assay can directly be translated to accelerate existing tethered particle-based, single-molecule biosensing applications.

Sono-Polymerization of Poly(ethylene glycol)-Based Nanoparticles for Targeted Drug Delivery.

Engineering functional nanoparticles (NPs) with low nonspecific interactions and a high specific targeting property is highly desired for improved drug delivery. Herein, we report a targeted poly(ethylene glycol) (PEG)-based chemotherapy system synthesized via a catalyst-free sono-polymerization process for drug delivery. The polymerization process was fast (20 min), and different monomers were able to be polymerized to form NPs in a one-pot process. Glutathione (GSH)-responsive platinum prodrugs and fluorescent dyes could be encapsulated in NPs by amidation formation. Cyclic peptides containing Arg-Gly-Asp (RGD)-modified PEG-based NPs possessed a much higher cell targeting (∼90%) than the unmodified PEG-based NPs (∼10%) after a 12 h incubation with U87 MG cells, which could improve drug delivery efficacy. The IC50 (50% inhibitory concentration) could also be reduced more than 50% compared to the nontargeted PEG-based NPs. Importantly, these PEG-based NPs can be freeze-dried into a powder form and redispersed in an aqueous solution without aggregation, which may facilitate the storage and transportation of nanomedicine. This study establishes a green and efficient method to engineer targeted drug carriers for drug delivery.

Advances in surface-coated single-walled carbon nanotubes as near-infrared photoluminescence emitters for single-particle tracking applications in biological environments

Single-particle tracking (SPT) represents a powerful tool for revealing the single-molecule dynamics in a number of biological processes in live cells and biological tissue. Single-walled carbon nanotubes (SWCNTs) are promising photoluminescence emitters for SPT applications in various biological environments due to their characteristic large-aspect-ratio structures along with their bright and stable near-infrared (NIR) photoluminescence, which are invaluable for long-term video-rate imaging and tracking applications at the single-molecule level with high signal-to-noise ratios (SNRs). Recent advances in applying SWCNTs as NIR photoluminescence emitters have highlighted the understanding of brain tissue organization at the nanometer scale. In the first section, this review article summarizes the latest advances in different surface coatings commonly used for encapsulating SWCNT surfaces via molecular self-assembly in order to obtain surface-coated nanotubes with low cytotoxicity and minimal nonspecific interactions with live cells while maintaining their emission of bright photoluminescence to enable long-term photoluminescent imaging and tracking at the single-nanotube level in biological environments. The second section offers a comparison of different excitation strategies of (6,5) SWCNTs to determine the best excitation wavelength for efficient video-rate imaging and tracking of individual nanotubes in live brain tissue for up to tens of minutes without inducing unacceptable phototoxicity or temperature increases. Finally, this review showcases that, by utilizing the photoluminescence tracking of single nanotubes combined with super-resolution single-molecule localization microscopy technologies, it is practical to elucidate the ultrafine nanometer-scale organization of the brain extracellular space (ECS) and probe the local rheological properties of young rat brain with a subdiffraction optical resolution down to 50 nm at a subwavelength accuracy of ~40 nm. The findings primarily indicate the great diversity of the brain ECS and the inhomogeneous properties of the local viscosity in live brain tissue. Overall, because of their advantages of low cytotoxicity, bright photoluminescence, high SNRs (~25), and deep tissue penetration (~100 μm) for long-term video-rate imaging and tracking at the single-nanotube level under 845 nm excitation (K-momentum exciton–phonon sideband, KSB), phospholipid-polyethylene glycol-coated SWCNTs hold great potential as NIR photoluminescence emitters for single-particle tracking in biological environments, as exemplified here in live brain tissue, and may find extended applications in elucidating the fundamental roles of the brain ECS in various biological processes, such as sleep, memory, aging, brain tumor progression, and neurodegenerative disease development.

Creation of antifouling microarrays by photopolymerization of zwitterionic compounds for protein assay and cell patterning

Nonspecific binding or adsorption of biomolecules presents as a major obstacle to higher sensitivity, specificity and reproducibility in microarray technology. We report herein a method to fabricate antifouling microarray via photopolymerization of biomimetic betaine compounds. In brief, carboxybetaine methacrylate was polymerized as arrays for protein sensing, while sulfobetaine methacrylate was polymerized as background. With the abundant carboxyl groups on array surfaces and zwitterionic polymers on the entire surfaces, this microarray allows biomolecular immobilization and recognition with low nonspecific interactions due to its antifouling property. Therefore, low concentration of target molecules can be captured and detected by this microarray. It was proved that a concentration of 10ngmL−1 bovine serum albumin in the sample matrix of bovine serum can be detected by the microarray derivatized with anti-bovine serum albumin. Moreover, with proper hydrophilic-hydrophobic designs, this approach can be applied to fabricate surface-tension droplet arrays, which allows surface-directed cell adhesion and growth. These light controllable approaches constitute a clear improvement in the design of antifouling interfaces, which may lead to greater flexibility in the development of interfacial architectures and wider application in blood contact microdevices.

Biodegradable zwitterionic sulfobetaine polymer and its conjugate with paclitaxel for sustained drug delivery.

The applicability of FDA-approved biodegradable aliphatic polyesters has been significantly restricted because they are hydrophobic and lack functionalities. Recently zwitterionic polymers have emerged as promising hydrophilic biomaterials, but most of the reported zwitterionic polymers are non-biodegradable. This study reports a novel aliphatic polyester-based zwitterionic polymer and the corresponding polymer-drug conjugate. Their aliphatic polyester and zwitterionic components provide them with high enzymatic degradability and low nonspecific interactions with biomolecules, respectively. While the zwitterionic polymer did not show noticeable cytotoxicity, the corresponding polymer-anticancer drug conjugate exhibited acid-sensitive sustained drug release, remarkable effectiveness in killing cancer cells, as well as the ready cellular internalization. This work lays a foundation for the further development of synthetic biodegradable zwitterionic polymer-based materials which potentially may have broad and significant biomedical applications.

Molecular insights for the biological interactions between polyethylene glycol and cells.

As the gold standard polymer for drug delivery system, polyethylene glycol (PEG) has excellent biocompatibility. It's reported that the low nonspecific interactions between PEG and body contribute to its biocompatibility. However, here we discover dynamic biological interactions exist between PEG and cells on the molecular level. PEG (2 kD) can induce metabolism modulations and survival autophagy by creating an intracellular hypoxic environment, which act as cellular survival strategies in response to the hypoxia. In the cellular adaption process during hypoxia, PEG-treated cells decrease energy consumption by reducing cell growth rate, increase energy supply by amino acid catabolism in a short period, and survival autophagy over a relatively long period, to keep energy homeostasis and survival. Our research provides molecular insights for understanding the mechanism underlying the excellent biocompatibility of PEG, which will be of fundamental importance for further related studies on other polymers and development of polymeric materials with improved characteristics.

Optimization of Magneto-thermally Controlled Release Kinetics by Tuning of Magnetoliposome Composition and Structure

Stealth (PEGylated) liposomes have taken a central role in drug formulation and delivery combining efficient transport with low nonspecific interactions. Controlling rapid release at a certain location and time remains a challenge dependent on environmental factors. We demonstrate a highly efficient and scalable way to produce liposomes of any lipid composition containing homogeneously dispersed monodisperse superparamagnetic iron oxide nanoparticles in the membrane interior. We investigate the effect of lipid composition, particle concentration and magnetic field actuation on colloidal stability, magneto-thermally actuated release and passive release rates. We show that the rate and amount of encapsulated hydrophilic compound released by actuation using alternating magnetic fields can be precisely controlled from stealth liposomes with high membrane melting temperature. Extraordinarily low passive release and temperature sensitivity at body temperature makes this a promising encapsulation and external-trigger-on-demand release system. The introduced feature can be used as an add-on to existing stealth liposome drug delivery technology.

Monodisperse Dual Plasmonic Au@Cu2-xE (E= S, Se) Core@Shell Supraparticles: Aqueous Fabrication, Multimodal Imaging, and Tumor Therapy at in Vivo Level.

We herein report aqueous fabrication of well-defined Au@Cu2-xE (E = S, Se) core@shell dual plasmonic supraparticles (SPs) for multimodal imaging and tumor therapy at the in vivo level. By means of a modified self-limiting self-assembly based strategy, monodisperse core@shell dual plasmonic SPs, including spherical Au@Cu2-xS SPs, Au@Cu2-xSe SPs, and rod-like Au@Cu2-xS SPs, are reliably and eco-friendly fabricated in aqueous solution. Due to plasmonic coupling from the core and shell materials, the as-prepared hybrid products possess an extremely large extinction coefficient (9.32 L g-1 cm-1 for spherical Au@Cu2-xS SPs) at 808 nm, which endows their excellent photothermal effect. Furthermore, the hybrid core@shell SPs possess the properties of good biocompatibility, low nonspecific interactions, and high photothermal stability. So, they show favorable performances for photoacoustic imaging and X-ray computed tomography imaging as well as photothermal therapy of tumors, indicating their application potentials in biological field.

Hyperbranched Polyglycerol Grafting on the Surface of Silica-Coated Nanoparticles for High Colloidal Stability and Low Nonspecific Interaction

Silica coating is widely used for protecting nanoparticles from aggregation and in transforming them into functional nanoparticles of 10–100 nm size. However, synthesis of silica-coated nanoparticles of <50 nm size with low surface charge, high colloidal stability, and minimum nonspecific interaction with the bioenvironment is very challenging. Here, we report a generalized approach of hyperbranched polyglycerol grafting on the surface of silica-coated nanoparticles that significantly improves their colloidal stability and minimizes nonspecific interaction with biological interfaces. Method involves transformation of 5–10 nm hydrophobic nanoparticles into silica-coated and primary amine-terminated nanoparticles of <30 nm hydrodynamic size followed by ring opening polymerization of glycidol at the nanoparticle surface. Resultant hyperbranched polyglycerol grafted nanoparticles have <50 nm hydrodynamic size, ±5 to 10 mV zeta potential, high colloidal stability, and low nonspecific interaction with live cell...

Planar Functionalized Surfaces for Direct Immunoaffinity Desorption/Ionization Mass Spectrometry.

Recent studies show that the haptoglobin phenotype in individuals with diabetes mellitus is an important factor for predicting the risk of myocardial infarction, cardiovascular death, and stroke. Current methods for haptoglobin phenotyping include PCR and gel electrophoresis. A need exists for a reliable method for high-throughput clinical applications. Mass spectrometry (MS) can in principle provide fast phenotyping because haptoglobin α 1 and α 2, which define the phenotype, have different molecular masses. Because of the complexity of the serum matrix, an efficient and fast enrichment technique is necessary for an MS-based assay. MALDI plates were functionalized by ambient ion landing of electrosprayed antihaptoglobin antibody. The array was deposited on standard indium tin oxide slides. Fast immunoaffinity enrichment was performed in situ on the plate, which was further analyzed by MALDI-TOF MS. The haptoglobin phenotype was determined from the spectra by embedded software script. The MALDI mass spectra showed ion signals of haptoglobin α subunits at m/z 9192 and at m/z 15 945. A cohort of 116 sera was analyzed and the reliability of the method was confirmed by analyzing the identical samples by Western blot. One hundred percent overlap of results between the direct immunoaffinity desorption/ionization MS and Western Blot analysis was found. MALDI plates modified by antihaptoglobin antibody using ambient ion landing achieve low nonspecific interactions and efficient MALDI ionization and are usable for quick haptoglobin phenotyping.

Oriented Bioconjugation of Unmodified Antibodies to Quantum Dots Capped with Copolymeric Ligands as Versatile Cellular Imaging Tools.

Distinctive optical properties of inorganic quantum dot (QD) nanoparticles promise highly valuable probes for fluorescence-based detection methods, particularly for in vivo diagnostics, cell phenotyping via multiple markers or single molecule tracking. However, despite high hopes, this promise has not been fully realized yet, mainly due to difficulties at producing stable, nontoxic QD bioconjugates of negligible nonspecific binding. Here, a universal platform for antibody binding to QDs is presented that builds upon the controlled functionalization of CdSe/CdS/ZnS nanoparticles capped with a multidentate dithiol/zwitterion copolymer ligand. In a change-of-paradigm approach, thiol groups are concomitantly used as anchoring and bioconjugation units to covalently bind up to 10 protein A molecules per QD while preserving their long-term colloidal stability. Protein A conjugated to QDs then enables the oriented, stoichiometrically controlled immobilization of whole, unmodified antibodies by simple incubation. This QD-protein A immobilization platform displays remarkable antibody functionality retention after binding, usually a compromised property in antibody conjugation to surfaces. Typical QD-protein A-antibody assemblies contain about three fully functional antibodies. Validation experiments show that these nanobioconjugates overcome current limitations since they retain their colloidal stability and antibody functionality over 6 months, exhibit low nonspecific interactions with live cells and have very low toxicity: after 48 h incubation with 1 μM QD bioconjugates, HeLa cells retain more than 80% of their cellular metabolism. Finally, these QD nanobioconjugates possess a high specificity for extra- and intracellular targets in live and fixed cells. The dithiol/zwitterion QD-protein A nanoconjugates have thus a latent potential to become an off-the-shelf tool destined to unresolved biological questions.

Parallel Magnetic Tweezers for Pulling CNS Axons Towards a Source of Repellent Factors

Regeneration of central nervous system (CNS) axons into hostile environments such as the glial scar that forms after the spinal cord injury is a crucial medical problem. Successful therapies will combine pharmaceutical interventions with physical techniques that control the mechanical environment along the axon path. Axon growth cones are highly motile regions that constantly probe the surrounding tissue and integrate external chemotactic stimuli into motility decisions such as elongation, retraction or turning. While a range of chemical guidance molecules and subsequent signaling pathways are well established, the effect of mechanics on axon elongation is largely unknown. We describe a novel in vitro system that enables direct force application to large number of CNS growth cones that are fluidically isolated from their cell bodies and exposed to controlled gradients of diffusing guidance cues. Growth cones were preferentially targeted by anti-neuronal cell adhesion molecule (NCAM) magnetic particles. Particles exhibited low non-specific interaction with axon shafts and resulting in a massively parallel magnetic tweezers platform. Results suggested that pulling with <10pN force can occasionally accelerate axon growth only if rho-associated protein kinase (ROCK) is inhibited. We show that up to 30pN force can be applied to a single magnetic particle. In separate experiments, a transient gradient of the repulsive guidance molecule Semaphorin 3A was formed in the axonal compartment. Our results suggest that developing CNS axons are not slowed down but deviated away from the source in a dose-dependent manner. This deviation was blocked by inhibiting ROCK or Calpain suggesting a multiplexed control over the growth cone cytoskeleton. Our current work aims to dissect the roles of Rho and Calpain pathways in the motility of growth cones, which are pulled towards a source of Sema3A.

Compact zwitterion-coated iron oxide nanoparticles for in vitro and in vivo imaging.

We have recently developed compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand coated superparamagnetic iron oxide nanoparticles (SPIONs) for use in various biomedical applications. The defining characteristics of ZDS-coated SPIONs are small hydrodynamic diameters, low non-specific interactions with fetal bovine serum, the opportunity for specific labeling, and stability with respect to time, pH, and salinity. We report here on the magnetic characterization of ZDS-coated SPIONs and their in vitro and in vivo performance relative to non-specific interactions with HeLa cells and in mice, respectively. ZDS-coated SPIONs retained the superparamagnetism and saturation magnetization (M(s)) of as-synthesized hydrophobic SPIONs, with M(s) = 74 emu g(-1) [Fe]. Moreover, ZDS-coated SPIONs showed only small non-specific uptake into HeLa cancer cells in vitro and low non-specific binding to serum proteins in vivo in mice.

A general route to xyloglucan-peptide conjugates for the activation of cellulose surfaces

Cellulose is an attractive supporting matrix for diverse biotechnological applications, including chromatography, diagnostics, and tissue replacement/scaffolding, due to its renewable resource status, low cost, and low non-specific interaction with biomolecules. In an effort to expand the biofunctionality of cellulose materials, we present here a versatile method for the synthesis of xyloglucan-peptide conjugates that harness the strong xyloglucan-cellulose binding interaction for gentle surface modification. Xylogluco-oligosaccharide aminoalditols (XGO-NH2) were coupled to both linear and cyclic peptides, which contained the endothelial cell epitope Arg-Gly-Asp, in a facile two-step approach employing diethyl squarate cross-linking. Subsequent xyloglucan endo-transglycosylase-mediated coupling of the resulting XGO-GRGDS (Gly-Arg-Gly-Asp-Ser) and XGO-c[RGDfK]-PEG-PEG (cyclo[Arg-Gly-Asp-(d-Phe)-Lys]-PEG-PEG; where PEG is 8-amino-3,6-dioxaoctanoic acid) conjugates into high molecular mass xyloglucan yielded xyloglucan-RGD peptide conjugates suitable for cellulose surface activation. Notably, use of XGO-squaramate as a readily accessible, versatile intermediate overcomes previous limitations of solid-phase synthetic approaches to XGO-peptide conjugates, and furthermore allows the method to be generalized to a wide variety of polypeptides and proteins, as well as diverse primary amino compounds.

Introducing surface-tethered poly(acrylic acid) brushes as 3D functional thin film for biosensing applications

Carboxyl groups of surface-tethered poly(acrylic acid) (PAA) brushes should be able to serve as versatile moieties for a wide range of chemical modifications, including an attachment of bioactive species that can act as sensing probes for biosensors. In this research, poly(tert-butyl acrylate) (Pt-BA) brushes were prepared by surface-initiated atom transfer radical polymerization of tert-butyl acrylate. PAA brushes were then obtained after removal of the tert-butyl groups from the Pt-BA brushes by acid hydrolysis. The carboxyl group density of the PAA brushes can be varied as a function of chain length or molecular weight. The reactivity of the carboxyl groups of PAA brushes towards the immobilization of biotin, a frequently used model bioactive probe in biosensing applications, was evaluated. Qualitative determination of streptavidin (SA) binding to the biotin-attached PAA brushes was verified by fluorescence microscopy. The efficiency of the PAA brushes to act as a three dimensional (3D) precursor layer for biosensing applications was further demonstrated using surface plasmon resonance (SPR), where the biotin-attached PAA brushes showed an enhanced signal for the biospecific binding of SA in comparison with a self-assembled monolayer (SAM) of a carboxyl-terminated alkanethiol, used as a model two-dimensional (2D) conventional precursor layer. The PAA brushes showed very low non-specific interactions with two other tested proteins of a similar pI but different sizes. This desirable feature should be highly beneficial for the development of biosensors.

Charge-Reversal Polyamidoamine Dendrimer for Cascade Nuclear Drug Delivery

Polyamidoamine (PAMAM) dendrimers with primary amine termini have been extensively explored as drug and gene carriers owing to their unique properties, but their amine-carried cationic charges cause nonspecific cellular uptakes, systemic toxicity and other severe problems in in vivo applications. In this article, we report a charge-reversal approach that latently deactivates PAMAM's primary amines to negatively charged acid-labile amides in order to inhibit its nonspecific interaction with cells, but regenerates the active PAMAM once in acidic environments. A cascade cancer cell nuclear drug delivery was achieved using the latently amidized PAMAM as the carrier conjugated with folic acid as the targeting group and a DNA-toxin drug camptothecin. The conjugate had low nonspecific interactions with cells, but easily entered cancer cells overexpressing folate receptors via receptor-mediated endocytosis. Subsequently, the endocytosed conjugate was transferred to acidic lysosomes, wherein the active PAMAM carrier was regenerated, escaped from the lysosome and then entered the nucleus for drug release. This reversible deactivation/activation makes PAMAM dendrimers useful nanocarriers for in vivo cancer cell nuclear-targeted drug delivery.

Neural stem cell adhesion and proliferation on phospholipid bilayers functionalized with RGD peptides

Peptide-functionalized materials show promise in controlling stem cell behavior by mimicking cell–matrix interactions. Supported lipid bilayers are an excellent platform for displaying peptides due to their ease of fabrication and low non-specific interactions with cells. In this paper, we report on the behavior of adult hippocampal neural stem cells (NSCs) on phospholipid bilayers functionalized with different RGD-containing peptides: either GGGNGEP RGDTYRAY (‘bsp-RGD(15)’) or G RGDSP. Fluid supported bilayers were prepared on glass surfaces by adsorption and fusion of small lipid vesicles incorporating synthetic peptide amphiphiles. NSCs adhered to bilayers with either GRGDSP or bsp-RGD(15) peptide. After 5 days in culture, NSCs formed neurosphere-like aggregates on GRGDSP bilayers, whereas on bsp-RGD(15) bilayers a large fraction of single adhered cells were observed, comparable to monolayer growth seen on laminin controls. NSCs retained their ability to differentiate into neurons and astrocytes on both peptide surfaces. This work illustrates the utility of supported bilayers in displaying peptide ligands and demonstrates that RGD peptides may be useful in synthetic culture systems for stem cells.

Electrosynthesized Surface‐Imprinted Conducting Polymer Microrods for Selective Protein Recognition

Novel surface-imprinted conducting polymer microrods are shown to selectively recognize the template protein, as demonstrated by competitive binding assays using fluorescence detection. The electrochemical template synthesis provides means for controlled fabrication and spatial confinement of the PEDOT/PSS polymer proposed in this work, which exhibits extraordinary low nonspecific interactions and is effectively turned into a selective protein sorbent upon imprinting.