Selective uptake and imaging of aptamer- and antibody-conjugated hollow nanospheres targeted to epidermal growth factor receptors overexpressed in head and neck cancer

Utilizing Peptide Ligand GPCRs to Image and Treat Pancreatic Cancer

It is estimated that early detection of pancreatic ductal adenocarcinoma (PDAC) could increase long-term patient survival by as much as 30% to 40% (Seufferlein, T. et al., Nat. Rev. Gastroenterol. Hepatol.2016, 13, 74–75). There is an unmet need for reagents that can reliably identify early cancerous or precancerous lesions through various imaging modalities or could be employed to deliver anticancer treatments specifically to tumor cells. However, to date, many PDAC tumor-targeting strategies lack selectivity and are unable to discriminate between tumor and nontumor cells, causing off-target effects or unclear diagnoses. Although a variety of approaches have been taken to identify tumor-targeting reagents that can effectively direct therapeutics or imaging agents to cancer cells (Liu, D. et al., J. Controlled Release2015, 219, 632–643), translating these reagents into clinical practice has been limited, and it remains an area open to new methodologies and reagents (O’Connor, J.P. et al., Nat. Rev. Clin. Oncol. 2017, 14, 169–186). G protein–coupled receptors (GPCRs), which are key target proteins for drug discovery and comprise a large proportion of currently marketed therapeutics, hold significant promise for tumor imaging and targeted treatment, particularly for pancreatic cancer.

Oligonucleotide aptamers against tyrosine kinase receptors: Prospect for anticancer applications

Transmembrane receptor tyrosine kinases (RTKs) play crucial roles in cancer cell proliferation, survival, migration and differentiation. Area of intense research is searching for effective anticancer therapies targeting these receptors and, to date, several monoclonal antibodies and small-molecule tyrosine kinase inhibitors have entered the clinic. However, some of these drugs show limited efficacy and give rise to acquired resistance. Emerging highly selective compounds for anticancer therapy are oligonucleotide aptamers that interact with their targets by recognizing a specific three-dimensional structure. Because of their nucleic acid nature, the rational design of advanced strategies to manipulate aptamers for both diagnostic and therapeutic applications is greatly simplified over antibodies. In this manuscript, we will provide a comprehensive overview of oligonucleotide aptamers as next generation strategies to efficiently target RTKs in human cancers.

Highly sensitive detection of epidermal growth factor receptor in lung cancer cells by aptamer-based target-/probe-mediated cyclic signal amplification

We develop an antibody-free fluorescence method for the epidermal growth factor receptor (EGFR) assay using aptamer-based target-/probe-mediated cyclic signal amplification. The method is highly sensitive with a detection limit of 0.16 fM, and it can be applied to detect EGFR in lung cancer cells, holding great potential in clinical diagnosis.

Synthesis of gold nanomaterials and their cancer-related biomedical applications: an update

Recently, the advances in the synthesis of new types of nanomaterials have created several opportunities in drug delivery and targeted therapy applications. Among the various nanostructures, gold nanostructures with controllable physical and chemical properties have received attention for various biomedical uses, including sensing of biomolecules, in vitro and in vivo bioimaging (as advanced contrast agents for photothermal and bioimaging techniques), photothermolysis of cancer cells, and targeted drug delivery. The attractive properties of gold nanomaterials, particularly, anti-angiogenic properties, are highly useful in a variety of cancers studies. In addition, they can bind many proteins and drugs and can be actively targeted to cancer cells over-expressing cell surface receptors and they are biocompatible in nature with a high atomic number, which directs to greater absorption of kilovoltage X-rays and provides greater contrast than standard agents. In this review, we have summarized the synthesis, structure and functionalization of gold nanostructures, and their biomedical applications with special reference to cancer studies.

Targeting tumor microenvironment to curb chemoresistance via novel drug delivery strategies

INTRODUCTION

Tumor is a heterogeneous mass of malignant cells co-existing with non-malignant cells. This co-existence evolves from the initial developmental stages of the tumor and is one of the hallmarks of cancer providing a protumorigenic niche known as tumor microenvironment (TME). Proliferation, invasiveness, metastatic potential and maintenance of stemness through cross-talk between tumors and its stroma forms the basis of TME.

AREAS COVERED

The article highlights the developmental phases of a tumor from dysplasia to the formation of clinically detectable tumors. The authors discuss the mechanistic stages involved in the formation of TME and its contribution in tumor outgrowth and chemoresistance. The authors have reviewed various approaches for targeting TME and its hallmarks along with their advantages and pitfalls. The authors also highlight cancer stem cells (CSCs) that are resistant to chemotherapeutics and thus a primary reason for tumor recurrence thereby, posing a challenge for the oncologists.

EXPERT OPINION

Recent understanding of the cellular and molecular mechanisms involved in acquired chemoresistance has enabled scientists to target the tumor niche and TME and modulate and/or disrupt this communication leading to the transformation from a tumor-supportive niche environment to a tumor-non-supporting environment and give synergistic results towards an effective management of cancer.

High Antifungal Activity against Candida Species of Monometallic and Bimetallic Nanoparticles Synthesized in Nanoreactors

Among all novel challenges nowadays worldwide, infectious disease is probably one of the most important. It is well-known that common treatments used include high doses of antibiotics, which are very invasive therapies for patients. These treatments are more intensive when the infection is related to multidrug resistant microorganisms. In this sense, in this work we report the use of reverse micelles to form less than 5 nm gold, silver, and gold-silver nanoparticles (NPs) with biological activity against five opportunistic Candida strains responsible of several diseases in human beings. As a result, we evaluate the interface properties and droplet-droplet interactions of micelles founding high fluidity in the polar head of the surfactant, necessary to form a flexible interaction channel in the "dimmer" micelle-micelle. In this condition, we form monodispersed, highly reactive NPs with sizes less than 5 nm with high antifungal activity against C. parapsilosis, C. Krusei, C. glabrata, C. guillermondii, and C. albicans, with minimum inhibitory concentrations (MIC₅₀) less than 0.7 ppm in all cases, the lowest reported to the best of our knowledge. These are very promising results to develop alternative therapies to treat fungal diseases in humans, animals, and plants, or to coat conventional surfaces in surgery rooms.

Aptamer Cell-Based Selection: Overview and Advances

Aptamers are high affinity single-stranded DNA/RNA molecules, produced by a combinatorial procedure named SELEX (Systematic Evolution of Ligands by Exponential enrichment), that are emerging as promising diagnostic and therapeutic tools. Among selection strategies, procedures using living cells as complex targets (referred as "cell-SELEX") have been developed as an effective mean to generate aptamers for heavily modified cell surface proteins, assuring the binding of the target in its native conformation. Here we give an up-to-date overview on cell-SELEX technology, discussing the most recent advances with a particular focus on cancer cell targeting. Examples of the different protocol applications and post-SELEX strategies will be briefly outlined.

Evaluating the Effect of Lidocaine on the Interactions of C-reactive Protein with Its Aptamer and Antibody by Dynamic Force Spectroscopy

Effects of medicine on the biomolecular interaction have been given extensive attention in biochemistry and biomedicine because of the complexity of the environment in vivo and the increasing opportunity of exposure to medicine. Herein, the effect of lidocaine on the interactions of C-reactive protein (CRP) with its aptamer and antibody under different temperature was investigated through dynamic force spectroscopy (DFS). The results revealed that lidocaine could reduce the binding probabilities and binding affinities of the CRP-aptamer and the CRP-antibody. An interesting discovery was that lidocaine had differential influences on the dynamic force spectra of the CRP-aptamer and the CRP-antibody. The energy landscape of the CRP-aptamer turned from two activation barriers to one after the treatment of lidocaine, while the one activation barrier in energy landscape of the CRP-antibody almost remained unchanged. In addition, similar results were obtained for 25 and 37 °C. In accordance with the result of molecular docking, the reduction of binding probabilities might be due to the binding of lidocaine on CRP. Additionally, the alteration of the dissociation pathway of the CRP-aptamer and the change of binding affinities might be caused by the conformational change of CRP, which was verified through synchronous fluorescence spectroscopy. Furthermore, differential effects of lidocaine on the interactions of CRP-aptamer and CRP-antibody might be attributed to the different dissociation processes and binding sites of the CRP-aptamer and the CRP-antibody and different structures of the aptamer and the antibody. This work indicated that DFS provided information for further research and comprehensive applications of biomolecular interaction, especially in the design of biosensors in complex systems.

Incorporating gold nanoclusters and target-directed liposomes as a synergistic amplified colorimetric sensor for HER2-positive breast cancer cell detection

Breast cancer is the second leading cause of cancer-related mortality in women. Successful development of sensitive nanoprobes for breast cancer cell detection is of great importance for breast cancer diagnosis and symptomatic treatment. Herein, inspired by the intrinsic peroxidase property of gold nanoclusters, high loading, and targeting ability of ErbB2/Her2 antibody functionalized liposomes, we report that gold nanoclusters-loaded, target-directed, functionalized liposomes can serve as a robust sensing platform for amplified colorimetric detection of HER2-positive breast cancer cells. This approach allows HER2-positive breast cancer cell identification at high sensitivity with high selectivity. In addition, the colorimetric “readout” offers extra advantages in terms of low-cost, portability, and easy-to-use applications. The practicality of this platform was further proved by successful detection of HER2-positive breast cancer cells in human serum samples and in breast cancer tissue, which indicated our proposed method has potential for application in cancer theranostics.

Multifunctionalization of Gold Nanoshells

Gold silica nanoshells have found many applications within the field of molecular biology, including as nanoscale sensors, the detection of biomarkers, and in the treatment of solid tumors using photothermal ablation. In order for them to be targeted to specific biomarkers while also remaining stable in biological media, it is often necessary to modify their surfaces with more than one functional group. Here, we describe how to create multifunctional gold nanoshells that can be used to either target specific tumor types in vivo or for the detection of biomarkers using biological specimen.

Nanoparticles for radiooncology: Mission, vision, challenges

Cancer is one of the leading non-communicable diseases with highest mortality rates worldwide. About half of all cancer patients receive radiation treatment in the course of their disease. However, treatment outcome and curative potential of radiotherapy is often impeded by genetically and/or environmentally driven mechanisms of tumor radioresistance and normal tissue radiotoxicity. While nanomedicine-based tools for imaging, dosimetry and treatment are potential keys to the improvement of therapeutic efficacy and reducing side effects, radiotherapy is an established technique to eradicate the tumor cells. In order to progress the introduction of nanoparticles in radiooncology, due to the highly interdisciplinary nature, expertise in chemistry, radiobiology and translational research is needed. In this report recent insights and promising policies to design nanotechnology-based therapeutics for tumor radiosensitization will be discussed. An attempt is made to cover the entire field from preclinical development to clinical studies. Hence, this report illustrates (1) the radio- and tumor-biological rationales for combining nanostructures with radiotherapy, (2) tumor-site targeting strategies and mechanisms of cellular uptake, (3) biological response hypotheses for new nanomaterials of interest, and (4) challenges to translate the research findings into clinical trials.

Chemically engineered persistent luminescence nanoprobes for bioimaging

Imaging nanoprobes are a group of nanosized agents developed for providing improved contrast for bioimaging. Among various imaging probes, optical sensors capable of following biological events or progresses at the cellular and molecular levels are actually actively developed for early detection, accurate diagnosis, and monitoring of the treatment of diseases. The optical activities of nanoprobes can be tuned on demand by chemists by engineering their composition, size and surface nature. This review will focus on researches devoted to the conception of nanoprobes with particular optical properties, called persistent luminescence, and their use as new powerful bioimaging agents in preclinical assays.

A Cholecystokinin B Receptor-Specific DNA Aptamer for Targeting Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinomas (PDACs) constitutively express the G-protein-coupled cholecystokinin B receptor (CCKBR). In this study, we identified DNA aptamers (APs) that bind to the CCKBR and describe their characterization and targeting efficacy. Using dual SELEX selection against “exposed” CCKBR peptides and CCKBR-expressing PDAC cells, a pool of DNA APs was identified. Further downselection was based on predicted structures and properties, and we selected eight APs for initial characterizations. The APs bound specifically to the CCKBR, and we showed not only that they did not stimulate proliferation of PDAC cell lines but rather inhibited their proliferation. We chose one AP, termed AP1153, for further binding and localization studies. We found that AP1153 did not activate CCKBR signaling pathways, and three-dimensional Confocal microscopy showed that AP1153 was internalized by PDAC cells in a receptor-mediated manner. AP1153 showed a binding affinity of 15 pM. Bioconjugation of AP1153 to the surface of fluorescent NPs greatly facilitated delivery of NPs to PDAC tumors in vivo. The selectivity of this AP-targeted NP delivery system holds promise for enhanced early detection of PDAC lesions as well as improved chemotherapeutic treatments for PDAC patients.

Physical characterization of nanoparticle size and surface modification using particle scattering diffusometry

As the field of colloidal science continues to expand, tools for rapid and accurate physiochemical characterization of colloidal particles will become increasingly important. Here, we present Particle Scattering Diffusometry (PSD), a method that utilizes dark field microscopy and the principles of particle image velocimetry to measure the diffusivity of particles undergoing Brownian motion. PSD measures the diffusion coefficient of particles as small as 30 nm in diameter and is used to characterize changes in particle size and distribution as a function of small, label-free, surface modifications of particles. We demonstrate the rapid sizing of particles using three orders-of-magnitude less sample volume than current standard techniques and use PSD to quantify particle uniformity. Furthermore, PSD is sensitive enough to detect biomolecular surface modifications of nanometer thickness. With these capabilities, PSD can reliably aid in a wide variety of applications, including colloid sizing, particle corona characterization, protein footprinting, and quantifying biomolecule activity.

Multifaceted analyses of the interactions between human heart type fatty acid binding protein and its specific aptamers

BACKGROUND

Aptamer-protein interaction studies have been mainly confined to dissociation constant (K_d) determination. A combinatorial approach involving limited proteolysis mass spectroscopy, molecular docking and CD studies is reported here to elucidate the specific interactions involved.

METHODS

To generate aptamers specific for human FABP3, SELEX was performed incorporating counter SELEX cycles against control FABPs and GST tag, followed by their characterization by EMSA, CD and SVD analysis. Based on computationally obtained aptamer-protein complex models, the interacting aptamer, and protein residues were predicted and supported by limited proteolysis experiments.

RESULTS

Two aptamers N13 and N53 specific for human fatty acid binding protein (FABP3) were isolated with corresponding K_d of 0.0743±0.0142μM and 0.3337±0.1485μM for FABP3 interactions. Both aptamers possess stable B-DNA structures at salt concentration of 100mM and pH range (6-9). The N13 aptamer led interaction involved 3 salt bridges and 2 hydrogen bonds, whereas N53 had 2 salt bridges with 8 hydrogen and 7 hydrophobic interactions.

CONCLUSIONS

The aptamers generated are the first to be reported against human FABP3. The higher interaction footprint of N53 incited synergistic conformational changes in both N53 and FABP3 during interaction, leading to a decline in binding affinity in comparison to N13 which corroborated to the calculated K_d values.

GENERAL SIGNIFICANCE

This combinatorial method may be used to retrieve the possible specific binding modes and interaction patterns involved in large aptamer-protein complexes. Thus the method can be exploited to identify the optimum aptamer length for in-depth structure-function studies and its tailored applications.

Comparative analysis of metallic nanoparticles as exogenous soft tissue contrast for live in vivo micro-computed tomography imaging of avian embryonic morphogenesis

BACKGROUND

Gestationally survivable congenital malformations arise during mid-late stages of development that are inaccessible in vivo with traditional optical imaging for assessing long-term abnormal patterning. MicroCT is an attractive technology to rapidly and inexpensively generate quantitative three-dimensional (3D) datasets but requires exogenous contrast media. Here we establish dose-dependent toxicity, persistence, and biodistribution of three different metallic nanoparticles in day 4 chick embryos.

RESULTS

We determined that 110-nm alkaline earth metal particles were nontoxic and persisted in the chick embryo for up to 24 hr postinjection with contrast enhancement levels at high as 1,600 Hounsfield units (HU). The 15-nm gold nanoparticles persisted with x-ray attenuation higher than that of the surrounding yolk and albumen for up to 8 hr postinjection, while 1.9-nm particles resulted in lethality by 8 hr. We identified spatial and temporally heterogeneous contrast enhancement ranging from 250 to 1,600 HU. With the most optimal 110-nm alkaline earth metal particles, we quantified an exponential increase in the tissue perfusion vs. distance from the dorsal aorta into the flank over 8 hr with a peak perfusion rate of 0.7 μm(2) /s measured at a distance of 0.3 mm.

CONCLUSIONS

These results demonstrate the safety, efficacy, and opportunity of nanoparticle based contrast media in live embryos for quantitative analysis of embryogenesis. Developmental Dynamics 245:1001-1010, 2016. © 2016 Wiley Periodicals, Inc.

A Functional CT Contrast Agent for In Vivo Imaging of Tumor Hypoxia

Hypoxia, which has been well established as a key feature of the tumor microenvironment, significantly influences tumor behavior and treatment response. Therefore, imaging for tumor hypoxia in vivo is warranted. Although some imaging modalities for detecting tumor hypoxia have been developed, such as magnetic resonance imaging, positron emission tomography, and optical imaging, these technologies still have their own specific limitations. As computed tomography (CT) is one of the most useful imaging tools in terms of availability, efficiency, and convenience, the feasibility of using a hypoxia-sensitive nanoprobe (Au@BSA-NHA) for CT imaging of tumor hypoxia is investigated, with emphasis on identifying different levels of hypoxia in two xenografts. The nanoprobe is composed of Au nanoparticles and nitroimidazole moiety which can be electively reduced by nitroreductase under hypoxic condition. In vitro, Au@BSA-NHA attain the higher cellular uptake under hypoxic condition. Attractively, after in vivo administration, Au@BSA-NHA can not only monitor the tumor hypoxic environment with CT enhancement but also detect the hypoxic status by the degree of enhancement in two xenograft tumors with different hypoxic levels. The results demonstrate that Au@BSA-NHA may potentially be used as a sensitive CT imaging agent for detecting tumor hypoxia.

Radio-nanomaterials for biomedical applications: state of the art

The incorporation of radioactive isotope(s) into conventional nanomaterials can bring extra properties which are not possessed by original materials. The resulting radioactive nanomaterials (radio-nanomaterials), with added physical/chemical properties, can be used as important tools for different biomedical applications. In this review, our goal is to provide an up-to-date overview on these applications using radio-nanomaterials. The first section illustrates the utilization of radionanomaterials for understanding of in vivo kinetics of their parent nano-materials. In the second section, we focus on two primary applications of radio-nanomaterials: imaging and therapeutic delivery. With various methods being used to form radio-nanomaterials, they can be used for positron emission tomography (PET), single-photon emission computed tomography (SPECT), and multimodal imaging. Therapeutic isotopes-loading radio-nanomaterials can possess selective killing efficacy of diseased cells (e.g. tumor cells) and can provide promises for certain isotopes which are not able to be used in a conventional manner. The successful and versatile biomedical applications of radio-nanomaterials warrants further investigations of those materials and their optimizations can pave the way to future imaging guidable, personalized treatments in patients.

Cetuximab-modified mesoporous silica nano-medicine specifically targets EGFR-mutant lung cancer and overcomes drug resistance

Drug resistance to tyrosine kinase inhibitor (TKI) is the main obstacle for efficient treatment of epidermal growth factor receptor (EGFR)-mutant lung cancer patients. Here we design a cetuximab-capped mesoporous silica nanoparticle (MP-SiO₂ NP) as the drug carrier to specifically target EGFR-mutant lung cancer cells and efficiently release loaded drugs including doxorubicin and gefitinib. This innovative nano-medicine can specifically target lung cancer cells with high EGFR expression rather than those with low EGFR level. Treatment of a gefitinib-resistant cell line derived from PC9 cell (PC9-DR) with the gefitinib-loaded cetuximab-capped MP-SiO₂ NP showed a significant inhibition of cell growth. Moreover, this nano-medicine successfully suppressed the progression of PC9-DR xenograft tumors. This tumor suppression was due to the endocytosis of large amount of nano-medicine and the effective gefitinib release induced by high glutathione (GSH) level in PC9-DR cells. Collectively, our study provides a novel approach to overcome EGFR-TKI resistance using cetuximab modified MP-SiO₂ NP, which holds strong potential for effective management of EGFR-mutant lung cancer.

Image-Guided Drug Delivery with Single-Photon Emission Computed Tomography: A Review of Literature

Tremendous resources are being invested all over the world for prevention, diagnosis, and treatment of various types of cancer. Successful cancer management depends on accurate diagnosis of the disease along with precise therapeutic protocol. The conventional systemic drug delivery approaches generally cannot completely remove the competent cancer cells without surpassing the toxicity limits to normal tissues. Therefore, development of efficient drug delivery systems holds prime importance in medicine and healthcare. Also, molecular imaging can play an increasingly important and revolutionizing role in disease management. Synergistic use of molecular imaging and targeted drug delivery approaches provides unique opportunities in a relatively new area called 'image-guided drug delivery' (IGDD). Single-photon emission computed tomography (SPECT) is the most widely used nuclear imaging modality in clinical context and is increasingly being used to guide targeted therapeutics. The innovations in material science have fueled the development of efficient drug carriers based on, polymers, liposomes, micelles, dendrimers, microparticles, nanoparticles, etc. Efficient utilization of these drug carriers along with SPECT imaging technology have the potential to transform patient care by personalizing therapy to the individual patient, lessening the invasiveness of conventional treatment procedures and rapidly monitoring the therapeutic efficacy. SPECT-IGDD is not only effective for the treatment of cancer but might also find utility in the management of several other diseases. Herein, we provide a concise overview of the latest advances in SPECT-IGDD procedures and discuss the challenges and opportunities for advancement of the field.

Constructing aptamer anchored nanovesicles for enhanced tumor penetration and cellular uptake of water soluble chemotherapeutics

Polymersomes represent a promising pharmaceutical vehicle for the delivery of hydrophilic therapeutic agents. However, modification of polymersomes with molecules that confer targeting functions remains challenging because of the strict requirements regarding the weight fractions of the hydrophilic and hydrophobic block polymers. In this study, based on the compatibility between cholesterol and polymeric carriers, polymersomes self-assembled by amphiphilic graft polyphosphazenes were endowed with a targeting function by incorporating the cholesterol-linked aptamer through a simple dialysis method. The aqueous interior of the polymersomes was employed to encapsulate water-soluble doxorubicin hydrochloride. In vivo experiments in tumor-bearing mice showed that the aptamer-anchored vesicle targeted accumulation at the tumor site, favorable penetration through tumor tissue, and incremental endocytosis into tumor cells. Correspondingly, the aptamer-anchored vesicle decreased systemic toxicity and effectively suppressed the growth of subcutaneous MCF-7 xenografts. These findings suggested that vesicles modified with targeted groups via hydrophobic supermolecular interactions could provide a platform for selective delivery of hydrophilic drug.

STATEMENT OF SIGNIFICANCE

Polymersomes have represented a promising type of pharmaceutical vehicles due to their predominant physical properties. However, it is still a challenge to endow polymersomes with active target function because of strict requirements of the weight fractions of hydrophilic polymer block to hydrophobic one. In this research, by taking advantage of the supermolecular interactions between amphiphilic graft polyphosphazene and cholesterol which was linked to aptamer AS1411, we prepared a targeted functional polymersome (PEP-DOX·HCl-Ap) through a simple method with high loading of water soluble anti-cancer drug doxorubicin hydrochloride. The in vivo experiments in MCF-7 tumor-bearing mice demonstrated several advantages of PEP-DOX·HCl-Ap vesicle such as prolonged circulation time in blood, targeted accumulation at tumor site, permeation through the tumor tissue and incremental endocytosis by tumor cells, which consequently resulted in the significantly improved anti-cancer efficacy. Moreover, this novel polymersome designed in this study has built a research platform to achieve targeted delivery of hydrophilic chemotherapeutics for cancer therapy.

Ultrasmall inorganic nanoparticles: State-of-the-art and perspectives for biomedical applications

Ultrasmall nanoparticulate materials with core sizes in the 1-3nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications. This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.

Cyclic Peptide-Decorated Self-Assembled Nanohybrids for Selective Recognition and Detection of Multivalent RNAs

Although there has been substantial advancement in the development of nanostructures, the development of self-assembled nanostructures that can selectively recognize multivalent targets has been very difficult. Here we show the proof of concept that topology-controlled peptide nanoassemblies can selectively recognize and detect a multivalent RNA target. We compared the differential behaviors of peptides in a linear or cyclic topology in terms of peptide-gold nanoparticle hybrid nanostructure formation, conformational stabilization, monovalent and multivalent RNA binding in vitro, and multivalent RNA recognition in live cells. When the topology-dependent selectivity amplification of the cyclic peptide hybrids is combined with the noninvasive nature of dark-field microscopy, the cellular localization of the viral Rev response element (RRE) RNA can be monitored in situ. Because intracellular interactions are often mediated by overlapping binding partners with weak affinity, the topology-controlled peptide assemblies can provide a versatile means to convert weak ligands into multivalent ligands with high affinity and selectivity.

Aptamers: versatile molecular recognition probes for cancer detection

In the past two decades, aptamers have emerged as a novel class of molecular recognition probes comprising uniquely-folded short RNA or single-stranded DNA oligonucleotides that bind to their cognate targets with high specificity and affinity. Aptamers, often referred to as "chemical antibodies", possess several highly desirable features for clinical use. They can be chemically synthesized and are easily conjugated to a wide range of reporters for different applications, and are able to rapidly penetrate tissues. These advantages significantly enhance their clinical applicability, and render them excellent alternatives to antibody-based probes in cancer diagnostics and therapeutics. Aptamer probes based on fluorescence, colorimetry, magnetism, electrochemistry, and in conjunction with nanomaterials (e.g., nanoparticles, quantum dots, single-walled carbon nanotubes, and magnetic nanoparticles) have provided novel ultrasensitive cancer diagnostic strategies and assays. Furthermore, promising aptamer targeted-multimodal tumor imaging probes have been recently developed in conjunction with fluorescence, positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI). The capabilities of the aptamer-based platforms described herein underscore the great potential they hold for the future of cancer detection. In this review, we highlight the most prominent recent developments in this rapidly advancing field.

Applications of aptamers in targeted imaging: state of the art

Aptamers are single-stranded oligonucleotides with high affinity and specificity to the target molecules or cells, thus they can serve as an important category of molecular targeting ligand. Since their discovery, aptamers have been rapidly translated into clinical practice. The strong target affinity/selectivity, cost-effectivity, chemical versatility and safety of aptamers are superior to traditional peptides- or proteins-based ligands which make them unique choices for molecular imaging. Therefore, aptamers are considered to be extremely useful to guide various imaging contrast agents to the target tissues or cells for optical, magnetic resonance, nuclear, computed tomography, ultrasound and multimodality imaging. This review aims to provide an overview of aptamers' advantages as targeting ligands and their application in targeted imaging. Further research in synthesis of new types of aptamers and their conjugation with new categories of contrast agents is required to develop clinically translatable aptamer-based imaging agents which will eventually result in improved patient care.

CLIC1 antibody conjugated nanoscale contrast agent as a sensitive and targeted molecular imaging probe for gallbladder cancer diagnosis

CLIC1 antibody-conjugated nano-scale contrast agents exhibit a fast and sensitive detection of gallbladder tumors and may be used in the future as powerful targeted molecular imaging probes for gallbladder cancer diagnosis.

Ultrasensitive and universal fluorescent aptasensor for the detection of biomolecules (ATP, adenosine and thrombin) based on DNA/Ag nanoclusters fluorescence light-up system

We report here an ultrasensitive strategy based on the recognition-induced conformational alteration of aptamer and fluorescence turn-on abilities of guanine-rich (G-rich) DNA sequence in proximity to silver nanoclusters for adenosine triphosphate (ATP), adenosine (A) and thrombin (TB) detection. Herein, we designed two tailored DNA sequences noted as complementary DNA (abbreviated as c-DNA) and signal probe DNA (abbreviated as s-DNA), respectively. c-DNA is designed as a special structure consisting of a sequence complementary to aptamer at the 3'-end and a guanine-rich DNA sequence at the 5'-end; s-DNA contains a cytosine-rich sequence responsible for Ag NCs templated synthesis at the 3'-end and a link sequence (part of aptamer) complementary to partial of the c-DNA at the 5'-end. In the presence of target, the aptamer associated with the target, resulting in the formation of duplex DNA (dsDNA), the DNA-Ag NCs thereafter could close to the guanine-rich sequence, leading to enhanced fluorescence signal readout. The widespread application of the sensing system is achieved success in the detection of three biomolecules. ATP, adenosine and thrombin in the range of 0.5-8.0 μM, 0.5-7.0 μM and 50-900 nM could be linearly detected with the detection limits of 91.6 nM, 103.4 nM and 8.4 nM, respectively. This label-free and turn-on fluorescent sensing system employing the mechanism proposed here turns out to be sensitive, selective, and convenient for the detection of biomolecules without washing and separation steps.

Nucleic Acid Bioconjugates in Cancer Detection and Therapy

Nucleoside- and nucleotide-based chemotherapeutics have been used to treat cancer for more than 50 years. However, their inherent cytotoxicities and the emergent resistance of tumors against treatment has inspired a new wave of compounds in which the overall pharmacological profile of the bioactive nucleic acid component is improved by conjugation with delivery vectors, small-molecule drugs, and/or imaging modalities. In this manner, nucleic acid bioconjugates have the potential for targeting and effecting multiple biological processes in tumors, leading to synergistic antitumor effects. Consequently, tumor resistance and recurrence is mitigated, leading to more effective forms of cancer therapy. Bioorthogonal chemistry has led to the development of new nucleoside bioconjugates, which have served to improve treatment efficacy en route towards FDA approval. Similarly, oligonucleotide bioconjugates have shown encouraging preclinical and clinical results. The modified oligonucleotides and their pharmaceutically active formulations have addressed many weaknesses of oligonucleotide-based drugs. They have also paved the way for important advancements in cancer diagnosis and treatment. Cancer-targeting ligands such as small-molecules, peptides, and monoclonal antibody fragments have all been successfully applied in oligonucleotide bioconjugation and have shown promising anticancer effects in vitro and in vivo. Thus, the application of bioorthogonal chemistry will, in all likelihood, continue to supply a promising pipeline of nucleic acid bioconjugates for applications in cancer detection and therapy.

Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant

We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials.

Aptamers as radiopharmaceuticals for nuclear imaging and therapy

Today, radiopharmaceuticals belong to the standard instrumentation of nuclear medicine, both in the context of diagnosis and therapy. The majority of radiopharmaceuticals consist of targeting biomolecules which are designed to interact with a disease-related molecular target. A plethora of targeting biomolecules of radiopharmaceuticals exists, including antibodies, antibody fragments, proteins, peptides and nucleic acids. Nucleic acids have some significant advantages relative to proteinaceous biomolecules in terms of size, production, modifications, possible targets and immunogenicity. In particular, aptamers (non-coding, synthetic, single-stranded DNA or RNA oligonucleotides) are of interest because they can bind a molecular target with high affinity and specificity. At present, few aptamers have been investigated preclinically for imaging and therapeutic applications. In this review, we describe the use of aptamers as targeting biomolecules of radiopharmaceuticals. We also discuss the chemical modifications which are needed to turn aptamers into valuable (radio-)pharmaceuticals, as well as the different radiolabeling strategies that can be used to radiolabel oligonucleotides and, in particular, aptamers.

Multifunctional magnetic-hollow gold nanospheres for bimodal cancer cell imaging and photothermal therapy

Multifunctional nanocomposites combining imaging and therapeutic functions have great potential for cancer diagnosis and therapy. In this work, we developed a novel theranostic agent based on hollow gold nanospheres (HGNs) and superparamagnetic iron oxide nanoparticles (SPIO). Taking advantage of the excellent magnetic properties of SPIO and strong near-infrared (NIR) absorption property of HGNs, such nanocomposites were applied to targeted magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) of cancer cells. In vitro results demonstrated they displayed significant contrast enhancement for T2-weighted MRI and strong PAI signal enhancement. Simultaneously, the nanocomposites exhibited a high photothermal effect under the irradiation of the near-infrared laser and can be used as efficient photothermal therapy (PTT) agents for selective killing of cancer cells. All these results indicated that such nanocomposites combined with MRI-PAI and PTT functionality can have great potential for effective cancer diagnosis and therapy.

Nucleic Acid Aptamers: An Emerging Tool for Biotechnology and Biomedical Sensing

Detection of small molecules or proteins of living cells provides an exceptional opportunity to study genetic variations and functions, cellular behaviors, and various diseases including cancer and microbial infections. Our aim in this review is to give an overview of selected research activities related to nucleic acid-based aptamer techniques that have been reported in the past two decades. Limitations of aptamers and possible approaches to overcome these limitations are also discussed.

Nanoshell-mediated targeted photothermal therapy of HER2 human breast cancer cells using pulsed and continuous wave lasers: an in vitro study

In this study, we report the apoptosis induction in HER2 overexpressed breast cancer cells using pulsed, continuous wave lasers and polyvinylpyrrolidone (PVP)-stabilized magneto-plasmonic nanoshells (PVP-MPNS) delivered by immunoliposomes. The immunoliposomes containing PVP-MPNS were fabricated and characterized. Heating efficiency of the synthesized nanostructures was calculated. The effect of functionalization on cellular uptake of nanoparticles was assessed using two cell lines of BT-474 and Calu-6. The best uptake result was achieved by functionalized liposome (MPNS-LAb) and BT-474. Also, the interaction of 514 nm argon (Ar) and Nd/YAG second harmonic 532-nm lasers with nanoparticles was investigated based on the temperature rise of the nanoshell suspension and the release value of 5(6)-carboxyfluorescein (CF) from CF/MPNS-loaded liposomes. The temperature increase of the suspensions after ten consecutive pulses of 532 nm and 5 min of irradiation by Ar laser were measured approximately 2 and 12 °C, respectively. The irradiation of CF/MPNS-loaded liposomes by Ar laser for 3 min resulted in 24.3 % release of CF, and in the case of 532 nm laser, the release was laser energy dependent. Furthermore, the comparison of CF release showed a higher efficiency for the Ar laser than by direct heating of nanoshell suspension using circulating water. The percentage of cell apoptosis after irradiation by Ar and 532 nm lasers were 44.6 and 42.6 %, respectively. The obtained results suggest that controlling the NP-laser interaction using optical properties of nanoshells and the laser parameters can be used to develop a new cancer therapy modality via targeted nanoshell and drug delivery.

A Highlight of Recent Advances in Aptamer Technology and Its Application

Aptamers and SELEX (systematic evolution of ligands by exponential enrichment) technology have gained increasing attention over the past 25 years. Despite their functional similarity to protein antibodies, oligonucleotide aptamers have many unique properties that are suitable for clinical applications and industrialization. Aptamers may be superior to antibodies in fields such as biomarker discovery, in vitro and in vivo diagnosis, precisely controlled drug release, and targeted therapy. However, aptamer commercialization has not occurred as quickly as expected, and few aptamer-based products have yet successfully entered clinical and industrial use. Thus, it is important to critically review some technical barriers of aptamer and SELEX technology per se that may impede aptamer development and application. To date, how to rapidly obtain aptamers with superior bioavailability over antibodies remains the key issue. In this review, we discuss different chemical and structural modification strategies aimed to enhance aptamer bioavailability. We also discuss improvements to SELEX process steps to shorten the selection period and improve the SELEX process success rate. Applications in which aptamers are particularly suited and perform differently or superior to antibodies are briefly introduced.

Aptamers and their applications in nanomedicine

Aptamers are composed of short RNA or single-stranded DNA sequences that, when folded into their unique 3D conformation, can bind to their targets with high specificity and affinity. Although functionally similar to protein antibodies, oligonucleotide aptamers offer several advantages over protein antibodies in biomedical and clinical applications. Through the enhanced permeability and retention effect, nanomedicines can improve the therapeutic index of a treatment and reduce side effects by enhancing accumulation at the disease site. However, this targets tumors passively and, thus, may not be ideal for targeted therapy. To construct ligand-directed "active targeting" nanobased delivery systems, aptamer-equipped nanomedicines have been tested for in vitro diagnosis, in vivo imaging, targeted cancer therapy, theranostic approaches, sub-cellular molecule detection, food safety, and environmental monitoring. This review focuses on the development of aptamer-conjugated nanomedicines and their application for in vivo imaging, targeted therapy, and theranostics.

Specific Recognition of Breast Cancer Cells In Vitro Using Near Infrared-Emitting Long-Persistence Luminescent Zn3Ga2Ge2O10:Cr3+ Nanoprobes

In this paper, near-infrared emitting long-persistence luminescent Zn₃Ga₂Ge₂O₁₀:Cr³⁺ (ZGG) nanoparticles with diameters of 30-100 nm and bright luminescence were prepared by a sol-gel synthesis method. After the surface amination, the nanoparticles were further bioconjugated with breast cancer-specific monoclonal antibody (anti-EpCAM) to form ZGG-EpCAM nanoprobes which can specifically target breast cancer cell lines (MCF7) in vitro. The results of in vitro images show that the luminescence signals from the cells treated with ZGG-EpCAM nanoprobes are stronger than those from cells treated with ZGG-unconjugated antibody, indicating that the prepared ZGG-EpCAM nanoprobes possessed excellent specific recognition capability. Furthermore, due to their long afterglow properties, the imaging could persist more than 1 h. Therefore, these nanoprobes could not only provide a high specificity detection method for cancer cells but also realize the long-time monitoring. Developed near-infrared emitting long-persistence luminescent nanoprobes will be expected to find new perspectives for cell therapy research and diagnosis applications.

Biomolecules-conjugated nanomaterials for targeted cancer therapy

Biomolecules perform vital functions in biology. These functional biomolecules with diverse modifications hold great promise for further applications in bioanalysis and cancer therapy. However, these functional biomolecules face challenges, especially in the field of drug delivery for cancer therapy. For example, functional biomolecules are typically unstable when taken up by cells, as they are easily digested by enzymes. To address this obstacle, nanomaterials have been employed as drug carriers or vehicles, which are powerful nanoplatforms for imaging and cancer treatment. Multifunctionality of these nanoplatforms offers great advantages over conventional reagents, including targeting to a diseased site to minimize systemic toxicity, and the ability to solubilize hydrophobic or labile drugs to improved pharmacokinetics. In this review, we summarize typical functional biomolecule-conjugated nanomaterials for targeting drug delivery. Under the appropriate conditions, targeted drug delivery can be achieved from a high density of biomolecules that are bound to the surface of nanomaterials, resulting in a high affinity for the targets. The high density of biomolecules then leads to a high local concentration, being able to prevent degradation by enzymes. Furthermore, biomolecule-nanomaterial conjugates have been identified to enter cells more easily than free biomolecules, and controllable drug release can then be obtained by a response to a stimulus, such as redox, pH, light, thermal, enzyme-trigged strategies. Now and in the future, with the development of artificial biomolecules as well as nanomaterials, targeted drug delivery based on elegant biomolecule-nanomaterial conjugation approaches is expected to achieve great versatility, additional functions, and further advances.

Fluorescent imaging of cancerous tissues for targeted surgery

To maximize tumor excision and minimize collateral damage are the primary goals of cancer surgery. Emerging molecular imaging techniques have made "image-guided surgery" developed into "molecular imaging-guided surgery", which is termed as "targeted surgery" in this review. Consequently, the precision of surgery can be advanced from tissue-scale to molecule-scale, enabling "targeted surgery" to be a component of "targeted therapy". Evidence from numerous experimental and clinical studies has demonstrated significant benefits of fluorescent imaging in targeted surgery with preoperative molecular diagnostic screening. Fluorescent imaging can help to improve intraoperative staging and enable more radical cytoreduction, detect obscure tumor lesions in special organs, highlight tumor margins, better map lymph node metastases, and identify important normal structures intraoperatively. Though limited tissue penetration of fluorescent imaging and tumor heterogeneity are two major hurdles for current targeted surgery, multimodality imaging and multiplex imaging may provide potential solutions to overcome these issues, respectively. Moreover, though many fluorescent imaging techniques and probes have been investigated, targeted surgery remains at a proof-of-principle stage. The impact of fluorescent imaging on cancer surgery will likely be realized through persistent interdisciplinary amalgamation of research in diverse fields.

Regenerative nanotechnology in oral and maxillofacial surgery

Regenerative nanotechnology is at the forefront of medical research, and translational medicine is a challenge to both scientists and clinicians. Although there has been an exponential rise in the volume of research generated about it for both medical and surgical uses, key questions remain about its actual benefits. Nevertheless, some people think that therapeutics based on its principles may form the core of applied research for the future. Here we give an account of its current use in oral and maxillofacial surgery, and implications and challenges for the future.