Advances in aptamer-based nuclear imaging

Molecular Engineering of Glycoaptamer Dual-Target Radionuclide Probes for PET/CT Imaging of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most malignant cancer types, characterized by a lack of efficient diagnostic and treatment methods in clinical practice. The development of effective targeted diagnosis and treatment for TNBC has become an important research focus. Here, we report the first proof-of-concept evidence of a glycoaptamer dual-target radionuclide probe (GDRP) for positron emission tomography/computed tomography (PET/CT) imaging of TNBC. The GDRP was created through precise molecular engineering of the aptamer AS1411, combined with three mannose ligands. The GDRP exhibited significantly increased serum stability and a high affinity for TNBC cells through a dual targeting mode. The advantages of our developed GDRP were further demonstrated by its excellent in vivo PET/CT dynamic imaging performance, featuring a long imaging window and high spatiotemporal resolution. This flexible method allows for the preparation of glycosylated functional nucleic acid molecular probes with high serum stability and tumor specificity. We anticipate that this PET/CT molecular probe will expand the development of glycoaptamer-based radioactive drugs and provides molecular tools for the clinical diagnosis of TNBC.

SYL3C Aptamer-DNA Tetrahedra Conjugates Enable Near-Infrared Fluorescent Imaging of Colorectal Cancer

Purpose

SYL3C is an optimized DNA aptamer with high selectivity and affinity for the epithelial cell adhesion molecule (EpCAM), an overexpressed tumor antigen in colorectal cancer (CRC). While its cellular affinity has been validated, in vivo studies are lacking.

Methods

This study modifies SYL3C with the fluorescent motif Cy7 to evaluate its metabolism and diagnostic potential in EpCAM-positive HT-29 xenograft mice using near-infrared fluorescence (NIRF). We also employ DNA Tetrahedra (DTN) to load the Cy7-DTN-SYL3C probe and assess whether this strategy improves circulation and tumor uptake of SYL3C.

Results

Cy7-SYL3C is primarily metabolized by the kidneys and enables targeted imaging of HT-29 tumors, outperforming untargeted Cy7-DTN. The DTN coupling strategy prolongs SYL3C metabolism and enhances tumor probe uptake about twice higher than Cy7-SYL3C over 24 hours.

Conclusion

This study presents preliminary evidence for the SYL3C aptamer's potential in vivo imaging of EpCAM-positive CRC. The DTN conjugation strategy may extend the aptamer's metabolic stability and improve tumor uptake, expanding its applications in CRC diagnosis and treatment.

Preclinical Evaluation of 68Ga-Labeled SL1 Aptamer for c-Met Targeted PET Imaging

Tyrosine protein kinase c-Met, encoded by the Met gene, is a membrane-associated receptor tyrosine kinase that is often aberrantly expressed in a wide range of tumors. The development of imaging probes specifically targeting c-Met is critical for improving cancer diagnostics. In this study, we successfully designed and fabricated an aptamer molecular imaging probe ([68Ga]Ga-NOTA-SL1) with high radiochemical purity (RCP), good stability in vitro, and high affinity for c-Met expressed tumors. As shown by the micro-PET/CT scanning, [68Ga]Ga-NOTA-SL1 efficiently imaged tumor models with varying c-Met expression. The quantitative analysis of micro-PET/CT showed tumor uptake of [68Ga]Ga-NOTA-SL1 in the HCC827 tumor models (30 min, 2.93 ± 0.64%ID/g; 60 min, 2.03 ± 0.67%ID/g; 90 min, 1.63 ± 0.61%ID/g), PC-9 tumor models (30 min, 2.1 ± 0.72%ID/g; 60 min, 1.7 ± 0.56%ID/g; 90 min, 1.33 ± 0.38%ID/g), and HCT116 tumor models (30 min, 1.4 ± 0.17%ID/g; 60 min, 1.23 ± 0.15%ID/g; 90 min, 0.97 ± 0.21%ID/g). The results of immunohistochemistry (IHC) further confirmed the targeting ability of [68Ga]Ga-NOTA-SL1 to c-Met from a molecular pathological perspective. The probe effectively imaged c-Met-positive tumors and demonstrated a favorable metabolism profile and targeting performance in non-small cell lung cancer (NSCLC) or colorectal cancer tumor models. Consequently, this probe shows promise as an imaging agent capable of providing valuable diagnostic insights into tumors with aberrant c-Met expression.

CAIX-targeted PET imaging agents based on acetazolamide small molecule for clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC), accounting for 65%-70%, is the most common subtype of renal cell cancers. Contrast-enhanced CT and MRI are still the predominant diagnostic modalities for renal carcinoma in clinical practice, but they cannot provide accurate diagnosis and staging, and molecular information related to tumor microenvironment. Carbonic anhydrase IX (CAIX), a transmembrane metalloenzyme on the cell surface and associated with hypoxia within the tumor, is emerging as a potential molecular target for both diagnosis and therapy in ccRCC. CAIX-targeted molecular imaging enables non-invasive visualization of ccRCC and guides treatment decision-making.

Combination of adenosine blockade and ferroptosis for photo-immunotherapy of triple negative breast cancer with aptamer-modified copper sulfide

Combination of immunotherapy and photothermal therapy (PTT) provides a promising therapeutic performance for tumors. However, it still faces negative feedback from suppressive factors such as adenosine. Herein, we developed a new nanodrug that can combine adenosine blockade and ferroptosis to promote the photoimmunotherapy of triple negative breast cancer (TNBC). The nanodrug, named CuS-PEG@Apt, was constructed via the modification of copper sulfide (CuS) nanoparticles with adenosine aptamer and PEG. CuS-PEG@Apt could be effectively enriched in the tumor site and locally generate a strong photothermal effect, directly ablating tumors and inducing immunogenic death (ICD). On the other hand, the aptamers could block the adenosine pathway to inhibit the immune suppression by adenosine, which further promoted the anti-tumor immunity. Moreover, the CuS nanoparticles could consume GSH and inhibit GPX4 to cause the ferroptosis of tumor cells. Collectively, CuS-PEG@Apt achieved potent efficacy of tumor suppression via the combination of PTT, immune activation and ferroptosis, representing an appealing platform for TNBC treatment.

Trends in Aptasensing and the Enhancement of Diagnostic Efficiency and Accuracy

The field of healthcare diagnostics is navigating complex challenges driven by evolving patient demographics and the rapid advancement of new technologies worldwide. In response to these challenges, these biosensors offer distinctive advantages over traditional diagnostic methods, such as cost-effectiveness, enhanced specificity, and adaptability, making their integration with point-of-care (POC) platforms more feasible. In recent years, aptasensors have significantly evolved in diagnostic capabilities through the integration of emerging technologies such as microfluidics, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems, wearable devices, and machine learning (ML), driving progress in precision medicine and global healthcare solutions. Moreover, these advancements not only improve diagnostic accuracy but also hold the potential to revolutionize early detection, reduce healthcare costs, and improve patient outcomes, especially in resource-limited settings. This Account examines key advancements, focusing on how scientific breakthroughs, including artificial intelligence (AI), have improved sensitivity and precision. Additionally, the integration of aptasensors with these technologies has enabled real-time monitoring and data analysis, fostering advances in personalized healthcare. Furthermore, the potential commercialization of aptasensor technologies could increase their availability in clinical settings and support their use as widespread solutions for global health challenges. Hence, this review discusses technological improvements, practical uses, and prospects while also focusing on the challenges surrounding standardization, clinical validation, and interdisciplinary collaboration for widespread application. Finally, ongoing efforts to address these challenges are key to ensure that aptasensors can be effectively implemented in diverse healthcare systems.

A Label-Free Aptasensor for the Detection of Sulfaquinoxaline Using AuNPs and Aptamer in Water Environment

Sulfaquinoxaline (SQX) is widely utilized in aquaculture and animal husbandry due to its broad antimicrobial spectrum and low cost. However, it is difficult to degrade, and there are relevant residues in the aquatic environment, which could be harmful to both the ecological environment and human health. As a new recognition molecule, the aptamer can be recognized with SQX with high affinity and specificity, and the aptamer is no longer adsorbed to AuNPs after binding to SQX, which weakens the catalytic effect of AuNPs. Consequently, an aptasensor for the detection of SQX was successfully developed. This aptasensor exhibits a linear range of 40-640 ng/mL, with a detection limit of 36.95 ng/mL, demonstrating both sensitivity and selectivity. The recoveries of this aptasensor in water samples ranged from 90 to 109.9%, which was quite in line with high-performance liquid chromatography. These findings suggest that the aptasensor is a valuable tool for detecting SQX in aqueous environmental samples.

Zwitterionic Peptides: From Mechanism, Design Strategies to Applications

Zwitterionic peptides, as a type of peptide composed of charged residues, are electrically neutral, which combine the advantages of zwitterionic materials and biological peptides, exhibiting hydrophilicity and programmable properties. As attractive candidates for resisting nonspecific adsorption of biomacromolecules and microorganisms, zwitterionic peptides have been applied in materials science, biomedicine, and biochemistry over the past decade. In this review, the development of zwitterionic peptides has been systematically outlined and analyzed, including their mechanisms, structure-function relationships, and design strategies. Furthermore, this review emphasizes and discusses their recent applications for developing functional coatings, biosensors, drug delivery systems, and engineering proteins. Finally, future research perspectives and challenges of zwitterionic peptides are also prospected and discussed. This review is intended to provide clarity and insight into the design and applications of zwitterionic peptides.

A Brief Review of Radiolabelling Nucleic Acid-Based Molecules for Tracking and Monitoring

The rise of nucleic acid-based therapeutics continues apace. At the same time, the need for radiolabelled oligonucleotides for determination of spatial distribution is increasing. Complex molecular structures with mostly multiple charges and low solubility in organic solvents increase the challenge of integrating radionuclides. In preclinical research, it is important to understand the fate of new drug candidates in biodistribution studies, target binding or biotransformation studies. Depending on a specific question, the selection of a respective radiolabelling strategy is crucial. Radiometals for molecular imaging with positron emission tomography or single-photon computed tomography generally require an attached chelating agent for stable complexation of the metal with the oligonucleotide, whereas labelling using carbon-11/-14 or tritium allows incorporation of the radioisotope into the native structure without altering it. Moreover, the suitability of direct radiolabelling of the oligonucleotide of interest or indirect radiolabelling, for example, by a two-step pretargeting approach, for the study design requires consideration. This review focuses on the challenges of radiolabelling nucleic acid-based molecules with beta-plus, gamma and beta-minus emitters and their use for tracking and monitoring.

An ultra-sensitive CRISPR-Cas12a and aptamer-based biosensor utilizing Entropy-driven catalytic DNA networks for precise detection of DNA Methyltransferase 1

DNA Methyltransferase 1 (DNMT1) serves as a crucial biomarker associated with various diseases and is essential for evaluating DNA methylation levels, diagnosing diseases, and evaluating prognosis. As a result, a convenient, quantitative, and sensitive assay for detecting DNMT1 is in high demand. However, current techniques for DNMT1 detection struggle to balance accuracy, low cost, and high sensitivity, limiting their clinical usefulness. To address this challenge, we have developed a DNMT1 detection method (CAED), which combines aptamer-specific recognition with a highly programmable Entropy-driven catalysis DNA network and is further integrated with the CRISPR-Cas12a system. This innovative approach achieves a detection limit as low as 90.9 fmol/L. To demonstrate the clinical applicability and significance of our CAED method, we successfully measured DNMT1 levels in 10 plasma samples 10 cervical tissue samples. These results underscore the potential of our method as an accurate, affordable, and ultra-sensitive tool for evaluating DNMT1 levels. This innovative method offers a potent means for assessing DNMT1 levels and significantly advances disease diagnosis and health risk prediction. Plus, it establishes an innovative design framework for CRISPR-Cas12a-based biosensors, tailored explicitly for enzyme content quantification.

Recent Progress of Multifunctional Molecular Probes for Triple-Negative Breast Cancer Theranostics

Breast cancer (BC) poses a significant threat to women's health, with triple-negative breast cancer (TNBC) representing one of the most challenging and aggressive subtypes due to the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. Traditional TNBC treatments often encounter issues such as low drug efficiency, limited tumor enrichment, and substantial side effects. Therefore, it is crucial to explore novel diagnostic and treatment systems for TNBC. Multifunctional molecular probes (MMPs), which integrate target recognition as well as diagnostic and therapeutic functions, introduce advanced molecular tools for TNBC theranostics. Using an MMP system, molecular drugs can be precisely delivered to the tumor site through a targeted ligand. Real-time dynamic monitoring of drug release achieved using imaging technology allows for the evaluation of drug enrichment at the tumor site. This approach enables accurate drug release, thereby improving the therapeutic effect. Therefore, this review summarizes the recent advancements in MMPs for TNBC theranostics, encompassing the design and synthesis of MMPs as well as their applications in the field of TNBC theranostics.

Aptamers: Promising Reagents in Biomedicine Application

Nucleic acid aptamers, often termed "chemical antibodies," are short, single-stranded DNA or RNA molecules, which are selected by SELEX. In addition to their high specificity and affinity comparable to traditional antibodies, aptamers have numerous unique advantages such as wider identification of targets, none or low batch-to-batch variations, versatile chemical modifications, rapid mass production, and lack of immunogenicity. These characteristics make aptamers a promising recognition probe for scientific research or even clinical application. Aptamer-functionalized nanomaterials are now emerged as a promising drug delivery system for various diseases with decreased side-effects and improved efficacy. In this review, the technological strategies for generating high-affinity and biostable aptamers are introduced. Moreover, the development of aptamers for their application in biomedicine including aptamer-based biosensors, aptamer-drug conjugates and aptamer functionalized nanomaterials is comprehensively summarized.

An overview of aptamer: Design strategy, prominent applications, and potential challenge in plants

Aptamers, serving as highly efficient molecular recognition and biotechnology tools, have garnered increasing interest in the realm of plant science in recent years. Aptamers are synthetic single-stranded short nucleotides or peptides, that bind targets with high specificity and affinity, triggering precise biological responses. As an alternative to antibodies, aptamers present promising avenues for advancement in biological researches. Aptamers function in a range of fields, encompassing cell signaling, drug development, biosensor technology, as well as botany, agricultural and forestry sciences. In this review, we introduce classifications and screening methods of aptamers, as well as aptamer-based technologies, highlighting their significant contributions to recent advancements. With their powerful functionality and ability to bind targets with high specificity and affinity, aptamers offer promising opportunities for breakthroughs in plant research.

Refining nanoprobes for monitoring of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a gastrointestinal immune disease that requires clear diagnosis, timely treatment, and lifelong monitoring. The diagnosis and monitoring methods of IBD mainly include endoscopy, imaging examination, and laboratory examination, which are constantly developed to achieve early definite diagnosis and accurate monitoring. In recent years, with the development of nanotechnology, the diagnosis and monitoring methods of IBD have been remarkably enriched. Nanomaterials, characterized by their minuscule dimensions that can be tailored, along with their distinctive optical, magnetic, and biodistribution properties, have emerged as valuable contrast agents for imaging and targeted agents for endoscopy. Through both active and passive targeting mechanisms, nanoparticles accumulate at the site of inflammation, thereby enhancing IBD detection. This review comprehensively outlines the existing IBD detection techniques, expounds upon the utilization of nanoparticles in IBD detection and diagnosis, and offers insights into the future potential of in vitro diagnostics. STATEMENT OF SIGNIFICANCE: Due to their small size and unique physical and chemical properties, nanomaterials are widely used in the biological and medical fields. In the area of oncology and inflammatory disease, an increasing number of nanomaterials are being developed for diagnostics and drug delivery. Here, we focus on inflammatory bowel disease, an autoimmune inflammatory disease that requires early diagnosis and lifelong monitoring. Nanomaterials can be used as contrast agents to visualize areas of inflammation by actively or passively targeting them through the intestinal mucosal epithelium where gaps exist due to inflammation stimulation. In this article, we summarize the utilization of nanoparticles in inflammatory bowel disease detection and diagnosis, and offers insights into the future potential of in vitro diagnostics.

Aptamers combined with immune checkpoints for cancer detection and targeted therapy: A review

In recent years, remarkable strides have been made in the field of immunotherapy, which has emerged as a standard treatment for many cancers. As a kind of immunotherapy drug, monoclonal antibodies employed in immune checkpoint therapy have proven beneficial for patients with diverse cancer types. However, owing to the extensive heterogeneity of clinical responses and the complexity and variability of the immune system and tumor microenvironment (TME), accurately predicting its efficacy remains a challenge. Recent advances in aptamers provide a promising approach for monitoring alterations within the immune system and TME, thereby facilitating targeted immunotherapy, particularly focused on immune checkpoint blockade, with enhanced antitumor efficiency. Aptamers have been widely used in tumor cell detection, biosensors, drug discovery, and biomarker screening due to their high specificity and high affinity with their targets. This review aims to comprehensively examine the research status and progress of aptamers in cancer diagnosis and immunotherapy, with a specific emphasis on those related to immune checkpoints. Additionally, we will discuss the future research directions and potential therapeutic targets for aptamer-based immune checkpoint therapy, aiming to provide a theoretical basis for targeting immunotherapy molecules and blocking tumor immune escape.

An efficient and universal In silico screening strategy for acquisition of high-affinity Aptamer and its application in analytical utility

Numerous aptamers against various targets have been identified through the technology of systematic evolution of ligands by exponential enrichment (SELEX), but the affinity of these aptamers are often insufficient due to the limitations of SELEX. Therefore, a more rational in silico screening strategy (ISS) was developed for efficient screening of high affinity aptamers, which took shape complementarity and thermodynamic stability into consideration. Neuron specific enolase (NSE), a tumor marker, was selected as the target molecule. In the screening process, three aptamer candidates with good shape complementarity, lower ΔG values, and higher ZDOCK scores were produced. The dissociation constant (Kd) of these candidates to NSE was determined to be 10.13 nM, 14.82 nM, and 2.76 nM, respectively. Each of them exhibited higher affinity to NSE than the parent aptamer (Kd = 23.83 nM). Finally, an antibody-free fluorescence aptasensor assay, based on the aptamer with the highest affinity, P-5C8G, was conducted, resulting in a limit of detection (LOD) value of 1.8 nM, which was much lower than the parental aptamer (P, LOD = 12.6 nM). The proposed ISS approach provided an efficient and universal strategy to improve the aptamer to have a high affinity and good analytical utility.

RNA nanostructures for targeted drug delivery and imaging

The RNA molecule plays a pivotal role in many biological processes by relaying genetic information, regulating gene expression, and serving as molecular machines and catalyzers. This inherent versatility of RNA has fueled significant advancements in the field of RNA nanotechnology, driving the engineering of complex nanoscale architectures toward biomedical applications, including targeted drug delivery and bioimaging. RNA polymers, serving as building blocks, offer programmability and predictability of Watson-Crick base pairing, as well as non-canonical base pairing, for the construction of nanostructures with high precision and stoichiometry. Leveraging the ease of chemical modifications to protect the RNA from degradation, researchers have developed highly functional and biocompatible RNA architectures and integrated them into preclinical studies for the delivery of payloads and imaging agents. This review offers an educational introduction to the use of RNA as a biopolymer in the design of multifunctional nanostructures applied to targeted delivery in vivo, summarizing physical and biological barriers along with strategies to overcome them. Furthermore, we highlight the most recent progress in the development of both small and larger RNA nanostructures, with a particular focus on imaging reagents and targeted cancer therapeutics in pre-clinical models and provide insights into the prospects of this rapidly evolving field.

Multifunctional Probe Based on "Chemical Antibody-Aptamer" for Noninvasive Detection of PD-L1 Expression in Cancer

Immune checkpoint inhibitors (ICIs) therapy based on programmed cell death ligand 1 (PD-L1) has shown significant development in treating several carcinomas, but not all patients respond to this therapy due to the heterogeneity of PD-L1 expression. The sensitive and accurate quantitative analysis of in vivo PD-L1 expression is critical for treatment decisions and monitoring therapy. In the present study, an aptamer-based dual-modality positron emission tomography/near-infrared fluorescence (PET/NIRF) imaging probe was developed, and its specificity and sensitivity to PD-L1 were assessed in vitro and in vivo. The probe precursor NOTA-Cy5-R1 was prepared by using automated solid-phase oligonucleotide synthesis. PET/NIRF dual-modality probe [68Ga]Ga-NOTA-Cy5-R1 was successfully synthesized and radiolabeled. The binding specificity of [68Ga]Ga-NOTA-Cy5-R1 to PD-L1 was evaluated by flow cytometry, fluorescence imaging, and cellular uptake in A375-hPD-L1 and A375 cells, and it showed good fluorescence properties and stability in vitro. In vivo PET/NIRF imaging studies illustrated that [68Ga]Ga-NOTA-Cy5-R1 can sensitively and specifically bind to PD-L1 positive tumors. Meanwhile, the rapid clearance of probes from nontarget tissues achieved a high signal-to-noise ratio. In addition, changes of PD-L1 expression in NCI-H1299 xenografts treated with cisplatin (CDDP) were sensitivity monitored by [68Ga]Ga-NOTA-Cy5-R1 PET imaging, and ex vivo autoradiography and western blot analyses correlated well with the change of PD-L1 expression in vivo. Overall, [68Ga]Ga-NOTA-Cy5-R1 showed notable potency as a dual-modality PET/NIRF imaging probe for visualizing tumors and monitoring the dynamic changes of PD-L1 expression, which can help to direct and promote the clinical practice of ICIs therapy.

Highly sensitive detection of Salmonella based on dual-functional HCR-mediated multivalent aptamer and amplification-free CRISPR/Cas12a system

BACKGROUND

Salmonella infection severely threatens human health and causes substantial medical and financial concerns. Sensitive and specific detection of Salmonella in food samples is crucial but remains challenging. While some traditional assays for S. typhimurium are reliable, they suffer from various limitations, such as being time-consuming (culture-based methods), involving intricate nucleic molecular extraction (polymerization chain reaction, PCR), and exhibiting inadequate sensitivity (enzyme-linked immunosorbent assay, ELISA). In this case, it is essential to establish a rapid, simple-operation, and sensitive method for monitoring S. typhimurium to preserve food quality and prevent contamination.

RESULT

Herein, an amplification-free detection method for Salmonella was developed by coupling the aptamer magnetic separation with dual-functional HCR (hybridization chain reaction)-scaffold multivalent aptamer and the activity of CRISPR/Cas12a. In the detection system, the dual-functional HCR-scaffold multivalent aptamer with high binding affinity and specificity was fabricated in advance by assembling numerous Salmonella specific aptamers on the long HCR products. In addition to the enhanced affinity, the HCR-multiApt also contains a massive amount of repeated CRISPR-targetable DNA units in its HCR scaffold, which could trigger the trans-cleavage activity of Cas12a. In the presence of target bacteria, the HCR-scaffold multivalent aptamer could attach on the surface of bacteria effectively and amplified the signal of bacteria into CRISPR/Cas12a based fluorescent readout. The proposed detection system allowed for ultrasensitive detection of Salmonella in a linear range from 100 to 107 cfu mL-1 with a LOD (limit of detection) of 2 cfu mL-1.

SIGNIFICANCE

The novel dual-functional HCR-multiApt presents a simple and powerful strategy for improving the aptamer binding affinity toward Salmonella. Simultaneously, integrating this dual-functional HCR-multiApt with the CRISPR/Cas12a system significantly enhances the sensitivity by cascade signal amplification in a nucleic acids amplification-free way. Finally, leveraging the versatility of the aptamer, this highly sensitive method can be further extended for application in the detection of other bacteria, food safety monitoring, or clinical diagnostics.

A novel His-tag-binding aptamer for recombinant protein detection and T cell-based immunotherapy

Screening novel aptamers for recombinant protein detection is of great significance in industrial mass production of antibody drugs. In addition, construction of structurally stable bispecific circular aptamers (bc-apts) may provide a tumor-targeted treatment strategy by simultaneously binding two different cell types. In this study, we obtained a high-affinity hexahistidine tag (His-tag)-binding aptamer 20S and explored its application in recombinant protein detection and T cell-based immunotherapy. We developed a new molecular beacon (MB) 20S-MB to detect His-tagged proteins in vitro and in vivo with high sensitivity and specificity, and the results showed high consistency with the enzyme-linked immunosorbent assay (ELISA). Moreover, we constructed two kinds of bc-apts by cyclizing 20S or another His-tag-binding aptamer, 6H5-MU, with Sgc8, which specifically recognizes protein tyrosine kinase 7 (PTK7) on tumor cells. After forming a complex with His-tagged OKT3, an anti-CD3 antibody for T cell activation, we utilized these aptamer-antibody complexes (ap-ab complex) to enhance cytotoxicity of T cells by linking T cells and target cells together, and 20S-sgc8 exhibited antitumor efficacy superior to that of 6H5-sgc8. In conclusion, we screened a novel His-tag-binding aptamer and used it to construct a new type of MB for rapid detection of recombinant proteins, as well as establish a feasible approach for T cell-based immunotherapy.

Aptamer-based technology for gastric cancer theranostics

Gastric cancer is one of the most common causes of cancer death worldwide. This cancer exhibits high molecular and phenotype heterogeneity. The overall survival rate for gastric cancer is very low because it is always diagnosed in the advanced stages. Therefore, early detection and treatment are of great significance. Currently, biomedical studies have tapped the potential clinical applicability of aptamer-based technology for gastric cancer diagnosis and targeted therapy. Herein, we summarize the enrichment and evolution of relevant aptamers, followed by documentation of the recent developments in aptamer-based techniques for early diagnosis and precision therapy for gastric cancers.

Advances in Radionuclides and Radiolabelled Peptides for Cancer Therapeutics

Radiopharmaceutical therapy, which can detect and treat tumours simultaneously, was introduced more than 80 years ago, and it has changed medical strategies with respect to cancer. Many radioactive radionuclides have been developed, and functional, molecularly modified radiolabelled peptides have been used to produce biomolecules and therapeutics that are vastly utilised in the field of radio medicine. Since the 1990s, they have smoothly transitioned into clinical application, and as of today, a wide variety of radiolabelled radionuclide derivatives have been examined and evaluated in various studies. Advanced technologies, such as conjugation of functional peptides or incorporation of radionuclides into chelating ligands, have been developed for advanced radiopharmaceutical cancer therapy. New radiolabelled conjugates for targeted radiotherapy have been designed to deliver radiation directly to cancer cells with improved specificity and minimal damage to the surrounding normal tissue. The development of new theragnostic radionuclides, which can be used for both imaging and therapy purposes, allows for more precise targeting and monitoring of the treatment response. The increased use of peptide receptor radionuclide therapy (PRRT) is also important in the targeting of specific receptors which are overexpressed in cancer cells. In this review, we provide insights into the development of radionuclides and functional radiolabelled peptides, give a brief background, and describe their transition into clinical application.

A nucleolin-activated polyvalent aptamer nanoprobe for the detection of cancer cells

Sensitive detection of cancer cells plays a critical role in early cancer diagnosis. Nucleolin, overexpressed on the surface of cancer cells, is regarded as a candidate biomarker for cancer diagnosis. Thus, cancer cells can be detected through the detection of membrane nucleolin. Herein, we designed a nucleolin-activated polyvalent aptamer nanoprobe (PAN) to detect cancer cells. In brief, a long single-stranded DNA with many repeated sequences was synthesized through rolling circle amplification (RCA). Then the RCA product acted as a scaffold chain to combine with multiple AS1411 sequences, which was doubly modified with fluorophore and quenching group, respectively. The fluorescence of PAN was initially quenched. Upon binding to target protein, the conformation of PAN changed, leading to the recovery of fluorescence. The fluorescence signal of cancer cells treated with PAN was much brighter compared with that of monovalent aptamer nanoprobes (MAN) at the same concentration. Furthermore, the binding affinity of PAN to B16 cells was proved to be 30 times higher than that of MAN by calculating the dissociation constants. The results indicated that PAN could specifically detect target cells, and this design concept has potential to become promising in cancer diagnosis.

Preliminary evaluation of a 64Cu-labeled DNA aptamer for PET imaging of glioblastoma

To develop a DNA aptamer-based PET tracer for imaging of glioblastoma. 5 mM of NOTA-AS1411, 60-min, and 37 °C were selected as the optimal condition for 64Cu radiolabeling of AS1411. 64Cu-NOTA-AS1411 remained stable in PBS and 100% mouse serum for at least six hours. From the PET images, 64Cu-NOTA-AS1411 tended to be excreted out through the kidneys and there was high tracer accumulation in the bladder. There was a higher tumor uptake in the AS1411 group than that in the control group. 64Cu-NOTA-AS1411 is a suitable potential PET tracer for imaging murine glioblastoma.

Aptamers as Smart Ligands for Targeted Drug Delivery in Cancer Therapy

Undesirable side effects and multidrug tolerance are the main holdbacks to the treatment of cancer in conventional chemotherapy. Fortunately, targeted drug delivery can improve the enrichment of drugs at the target site and reduce toxicity to normal tissues and cells. A targeted drug delivery system is usually composed of a nanocarrier and a targeting component. The targeting component is called a "ligand". Aptamers have high target affinity and specificity, which are identified as attractive and promising ligands. Therefore, aptamers have potential application in the development of smart targeting systems. For instance, aptamers are able to efficiently recognize tumor markers such as nucleolin, mucin, and epidermal growth factor receptor (EGFR). Besides, aptamers can also identify glycoproteins on the surface of tumor cells. Thus, the aptamer-mediated targeted drug delivery system has received extensive attention in the application of cancer therapy. This article reviews the application of aptamers as smart ligands for targeted drug delivery in cancer therapy. Special interest is focused on aptamers as smart ligands, aptamer-conjugated nanocarriers, aptamer targeting strategy for tumor microenvironment (TME), and aptamers that are specified to crucial cancer biomarkers for targeted drug delivery.

Photoactivated Nanohybrid for Dual-Nuclei MR/US/PA Multimodal-Guided Photothermal Therapy

Nanohybrids have gained immense popularity for the diagnosis and chemotherapy of lung cancer for their excellent biocompatibility, biodegradability, and targeting ability. However, most of them suffer from limited imaging information, low tumor-to-background ratios, and multidrug resistance, limiting their potential clinical application. Herein, we engineered a photoresponsive nanohybrid by assembling polypyrrole@bovine serum albumin (PPy@BSA) encapsulating perfluoropentane (PFP)/¹²⁹Xe for selective magnetic resonance (MR)/ultrasonic (US)/photoacoustic (PA) trimodal imaging and photothermal therapy of lung cancer, overcoming these drawbacks of single imaging modality and chemotherapy. The nanohybrid exhibited superior US, PA, and MR multimodal imaging performance for lung cancer detection. The high sensitivity of the nanohybrid to near-infrared light (NIR) resulted in a rapid increase in temperature in a low-intensity laser state, which initiated the phase transition of liquid PFP into the gas. The ultrasound signal inside the tumor, which is almost zero initially, is dramatically increased. Beyond this, it led to the complete depression of ¹⁹F/¹²⁹Xe Hyper-CEST (chemical exchange saturation transfer) MRI during laser irradiation, which can precisely locate lung cancer. In vitro and in vivo results of the nanohybrid exhibited a successful therapeutic effect on lung cancer. Under the guidance of imaging results, a sound effect of photothermal therapy (PTT) for lung cancer was achieved. We expect this nanohybrid and photosensitive behavior will be helpful as fundamental tools to decipher lung cancer in an earlier stage through trimodality imaging methods.

Radiolabeling of functional oligonucleotides for molecular imaging

Molecular imaging has greatly advanced basic biology and translational medicine through visualization and quantification of molecular events in a cellular context and living organisms. Nuclear medicine, including positron emission tomography (PET) and single-photon emission tomography (SPECT), is one of the most representative molecular imaging modalities which is widely used in clinical theranostics. Recently, numerous molecular imaging agents have been developed to improve the quality and expand the applicable diseases of molecular imaging. Based on the choice of specific imaging agents, molecular imaging is capable of studying tumor biological activities, detecting tumor metastasis, and imaging Alzheimer’s disease-related amyloid proteins. Among these imaging agents, functional oligonucleotides-based imaging probes are becoming increasingly important due to their unique features. Antisense oligonucleotides, small interfering RNA, and aptamers are privileged molecular tools in precision medicine for cancer diagnosis and treatment. These chemically synthesized oligonucleotides without batch-to-batch variations are flexible to incorporate with other molecules without affecting their functionalities. Therefore, through the combination of oligonucleotides with radioisotopes, a series of molecular imaging agents were developed in the past decades to achieve highly sensitive and accurate biomedical imaging modalities for clinical theranostic. Due to the nature of oligonucleotides, the strategies of oligonucleotide radiolabeling are different from conventional small molecular tracers, and the radiolabeling strategy with rational design is highly correlated to the imaging quality. In this review, we summarize recent advancements in functional oligonucleotide radiolabeling strategies and respective molecular imaging applications. Meanwhile, challenges and future development insights of functional oligonucleotide-based radiopharmaceuticals are discussed in the end.