Aptamer-based biosensors for virus protein detection.

Virus threatens life health seriously. The accurate early diagnosis of the virus is vital for clinical control and treatment of virus infection. Aptamers are small single-stranded oligonucleotides (DNAs or RNAs). In this review, we summarized aptasensors for virus detection in recent years according to the classification of the viral target protein, and illustrated common detection mechanisms in the aptasensors (colorimetry, fluorescence assay, surface plasmon resonance (SPR), surface-enhanced raman spectroscopy (SERS), electrochemical detection, and field-effect transistor (FET)). Furthermore, aptamers against different target proteins of viruses were summarized. The relationships between the different biomarkers of the viruses and the detection methods, and their performances were revealed. In addition, the challenges and future directions of aptasensors were discussed. This review will provide valuable references for constructing on-site aptasensors for detecting viruses, especially the SARS-CoV-2.

Synthesis and antioxidant activities of berberine 9-O-benzoic acid derivatives.

Although berberine (BBR) shows antioxidant activity, its activity is limited. We synthesized 9-O-benzoic acid berberine derivatives, and their antioxidant activities were screened via ABTS, DPPH, HOSC and FRAP assays. The para-position was modified with halogen elements on the benzoic acid ring, which led to an enhanced antioxidant activity and the substituent on the ortho-position was found to be better than the meta-position. Compounds 8p, 8c, 8d, 8i, 8j, 8l, and especially 8p showed significantly higher antioxidant activities, which could be attributed to the electronic donating groups. All the berberine derivatives possessed proper lipophilicities. In conclusion, compound 8p is a promising antioxidant candidate with remarkable elevated antioxidant activity and moderate lipophilicity.

Metal-organic frameworks for virus detection.

Virus severely endangers human life and health, and the detection of viruses is essential for the prevention and treatment of associated diseases. Metal-organic framework (MOF), a novel hybrid porous material which is bridged by the metal clusters and organic linkers, has become a promising biosensor platform for virus detection due to its outstanding properties including high surface area, adjustable pore size, easy modification, etc. However, the MOF-based sensing platforms for virus detection are rarely summarized. This review systematically divided the detection platforms into nucleic acid and immunological (antigen and antibody) detection, and the underlying sensing mechanisms were interpreted. The nucleic acid sensing was discussed based on the properties of MOF (such as metal ion, functional group, geometry structure, size, porosity, stability, etc.), revealing the relationship between the sensing performance and properties of MOF. Moreover, antibodies sensing based on the fluorescence detection and antigens sensing based on molecular imprinting or electrochemical immunoassay were highlighted. Furthermore, the remaining challenges and future development of MOF for virus detection were further discussed and proposed. This review will provide valuable references for the construction of sophisticated sensing platform for the detection of viruses, especially the 2019 coronavirus.

Tumor microenvironment responsive drug delivery systems.

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Dynamic DNA Assemblies in Biomedical Applications.

Deoxyribonucleic acid (DNA) has been widely used to construct homogeneous structures with increasing complexity for biological and biomedical applications due to their powerful functionalities. Especially, dynamic DNA assemblies (DDAs) have demonstrated the ability to simulate molecular motions and fluctuations in bionic systems. DDAs, including DNA robots, DNA probes, DNA nanochannels, DNA templates, etc., can perform structural transformations or predictable behaviors in response to corresponding stimuli and show potential in the fields of single molecule sensing, drug delivery, molecular assembly, etc. A wave of exploration of the principles in designing and usage of DDAs has occurred, however, knowledge on these concepts is still limited. Although some previous reviews have been reported, systematic and detailed reviews are rare. To achieve a better understanding of the mechanisms in DDAs, herein, the recent progress on the fundamental principles regarding DDAs and their applications are summarized. The relative assembly principles and computer-aided software for their designing are introduced. The advantages and disadvantages of each software are discussed. The motional mechanisms of the DDAs are classified into exogenous and endogenous stimuli-triggered responses. The special dynamic behaviors of DDAs in biomedical applications are also summarized. Moreover, the current challenges and future directions of DDAs are proposed.

Aptamer-Pyropheophorbide a Conjugates with Tumor Spheroid Targeting and Penetration Abilities for Photodynamic Therapy.

Pyropheophorbide a (Pyro) is a widely used photosensitizer for photodynamic therapy (PDT). However, poor water solubility, aggregation-induced fluorescence quenching, and lack of selectivity to targeted cells seriously limit its application. In this work, we prepared aptamer-Pyro conjugates (APCs) by linking Pyro to hydrophilic nucleic acid aptamer to enhance its water solubility and endow it with protein tyrosine kinase 7 (PTK7) overexpressed tumor spheroid specific targeting and penetration abilities for photodynamic therapy. The molecular conjugate was successfully synthesized and dissolved well in an aqueous solution. The APCs showed strong near-infrared fluorescence in the aqueous solution and produced singlet oxygen both in the solution and cells under laser irradiation, indicating its generation of singlet oxygen during PDT was guaranteed. Owing to the cancer cell targeting ability of the aptamer, the APCs specifically bound with PTK7 overexpressed cancerous cells and showed fluorescence signal for tumor cell imaging and diagnosis. The APCs exhibited favorable enhanced phototoxicity to target tumor cells compared with control cells. More importantly, due to the small size of the molecular conjugate, the APCs efficiently penetrated into the interior of multicellular tumor spheroids (MCTS) and caused cell damage. All these results indicated that the robust aptamer-Pyro conjugate is a promising selective tumor-targeting and penetrable molecule for cancer photodynamic therapy.

Tumor microenvironment and NIR laser dual-responsive release of berberine 9-O-pyrazole alkyl derivative loaded in graphene oxide nanosheets for chemo-photothermal synergetic cancer therapy.

A berberine 9-O-pyrazole alkyl derivative, a chemical compound (called B3) previously synthesized by our group, shows anti-cancer activity. However, B3 lacks targeting cytotoxicity to cancer cells, leading to obvious toxic side effects on normal cells. To solve this problem, here, we prepared a drug delivery system, namely, AS1411-GO/B3 for tumor targeting, in which nano-graphene oxide (GO) sheets were employed as the drug carrier, and the aptamer AS1411 was conjugated onto GO for tumor targeting. GO also had a photothermal effect, which helped the release of B3 from GO as well as the thermal cytotoxicity to cells. We found that the release of B3 could respond to acid conditions, indicating that the tumor intracellular environment could promote the release of B3, thus allowing it to perform chemotherapy effects. This system could also release B3 in response to photothermal heating, moreover, combined photothermal therapy and chemotherapy to improve the anticancer activity was achieved. This AS1411-GO/B3 platform with chemo-photothermal synergetic therapy provides a very promising treatment for tumors.

PtNPs-GNPs-MWCNTs-ß-CD nanocomposite modified glassy carbon electrode for sensitive electrochemical detection of folic acid.

A novel electrochemical sensor, platinum nanoparticles/graphene nanoplatelets/multi-walled carbon nanotubes/ß-cyclodextrin composite (PtNPs-GNPs-MWCNTs-ß-CD) modified carbon glass electrode (GCE), was fabricated and used for the sensitive detection of folic acid (FA). The PtNPs-GNPs-MWCNTs-ß-CD nanocomposite was easily prepared with an ultrasound-assisted assembly method, and it was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of FA at PtNPs-GNPs-MWCNTs-ß-CD/GCE was investigated in detail. Some key experimental parameters such as pH, amount of PtNPs-GNPs-MWCNTs-ß-CD composite, and scan rate were optimized. A good linear relationship (R2 = 0.9942) between peak current of cyclic voltammetry (CV) and FA concentration in the range 0.02-0.50 mmol L-1 was observed at PtNPs-GNPs-MWCNTs-ß-CD/GCE. The detection limit was 0.48 µmol L-1 (signal-to-noise ratio = 3). A recovery of 97.55-102.96% was obtained for the determination of FA in FA pills (containing 0.4 mg FA per pill) at PtNPs-GNPs-MWCNTs-ß-CD/GCE, indicating that the modified electrode possessed relatively high sensitivity and stability for the determination of FA in real samples.

Interfacing DNA with nanoparticles: Surface science and its applications in biosensing.

The knowledge on the mechanisms of DNA interfacing with nanoparticles holds great potential for the design, assembly and usage of DNA in biological applications. A wave of understanding and exploitation of the mechanisms in DNA-nanoparticles interfacial phenomenon has raised. Although some previous reviews have been reported, systematic and detailed reviews are rare. To achieve a better understanding of the mechanisms in the interaction between DNA and nanoparticles, here, we summarized the recent progresses on the fundamental principles regarding the DNA-nanoparticle interactions and their applications in biosensing. Special focus was put on inorganic nanoparticles such as metal nanoparticles, carbon-based materials, metal oxides and quantum dots. For each material, the surface properties, the interfacing mechanisms, and the kinetics and spatial control of DNA adsorption were summarized and discussed. We also highlighted some of the recent technologies based on DNA-NPs interactions for biomolecules detection. Finally, the challenges and future directions were discussed and proposed. This review provides a systematic understanding of the mechanisms in the interaction of DNA-nanoparticles, which, in turn, can inspire new insights for designing biosensors with improved properties.

A sensitive non-enzymatic electrochemical sensor based on acicular manganese dioxide modified graphene nanosheets composite for hydrogen peroxide detection.

In this work, a novel manganese dioxide-graphene nanosheets (MnO2-GNSs) composite was synthesized by a facile one-step hydrothermal method, in which manganese dioxide (MnO2) was fabricated by hydrothermal reduction of KMnO4 with GNSs. The structure and morphology of MnO2-GNSs composite were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). A sensitive non-enzymatic electrochemical sensor based on MnO2-GNSs composite for the detection of low concentration hydrogen peroxide (H2O2) was fabricated. The electrochemical properties of MnO2-GNSs composite modified glassy carbon electrode (MnO2-GNSs/GCE) were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometry. The observations confirmed that the fabricated sensor exhibited high electrocatalytic activity for oxidation of H2O2 owing to the catalytic ability of MnO2 particles and the conductivity of GNSs. Under the optimum conditions, the calibration curve was linear for the amperometric response versus H2O2 concentration over the range 0.5-350 µM with a low detection limit of 0.19 µM (S/N = 3) and high sensitivity of 422.10 µA mM-1 cm-2. The determination and quantitative analysis of H2O2 in antiseptic solution on MnO2-GNSs/GCE exhibited percent recovery of 96.50%-101.22% with relative standard deviation (RSD) of 1.48%-4.47%. The developed MnO2-GNSs/GCE might be a promising platform for the practical detection of H2O2 due to its prominent properties including excellent reproducibility, good anti-interference and repeatability.

Metal-organic frameworks for stimuli-responsive drug delivery.

Metal-organic framework (MOF), a novel hybrid porous material which is composited by metal ions and organic linkers, has drawn increasing attention and became a promising material in the biomedical field owing to their unique properties including large pore volume, high surface area, tunable pore size, versatile functionality and high drug loading efficiency. However, the MOF families and members, and the drug release mechanisms in MOF-based stimuli-responsive drug delivery systems (DDSs) are rarely summarized. Here, we systematically classified the families of MOF and introduced some representative members in MOF families. Moreover, the underlying drug release mechanisms were interpreted according to endogenous stimuli (include pH, glutathione (GSH), adenosine-triphosphate (ATP), ion, glucose, enzyme, H2S, and etc.) and the exogenous stimuli (include light, temperature, pressure, and etc.). Furthermore, the remaining challenges and future directions of DDSs based on MOF are discussed and proposed. This review revealed the relationship between the structure and properties of MOF. A better understanding of these release mechanisms under different stimuli would benefit the designing of sophisticated DDSs based on the promising material of MOF.

Iridium-catalyzed B-H insertion of sulfoxonium ylides and borane adducts: a versatile platform to α-boryl carbonyls.

Iridium-catalyzed boron-hydrogen bond insertion reactions of trimethylamine-borane and sulfoxonium ylides have been demonstrated, furnishing α-boryl ketones in moderate to excellent yields in most cases (51 examples; up to 84%). This practical and scalable insertion reaction showed broad substrate scope, high functional-group compatibility and could be applied in late-stage modification of structurally complex drug compounds. Further synthetic applications were also demonstrated.

Advances in aptamer screening technologies.

Systematic evolution of ligands by exponential enrichment (SELEX) is a well-established technology for the screening of aptamers binding to various targets with relatively high specificity and affinity. The screened aptamers have shown great achievements in bio-sensing and targeted therapeutics, which in turn stimulate continuous development of SELEX technology. To date, many SELEX technologies have been established, such as cell-SELEX, mag-SELEX, capillary electrophoresis SELEX and some novel modifications of SELEX. This review highlights current screening technologies and comprehensively pinpoints their principles, pros and cons. Some main aptamers screened by SELEX or involved in clinical trials are summarized. While, there are still challenges in obtaining of aptamer with high affinity and in an efficient way. The limitations and possible future directions on the screening of aptamers are also outlined.

Cancer protein biomarker discovery based on nucleic acid aptamers.

Identification of biomarkers is essential for diagnosis, targeted therapy and prognosis evaluation of diseases, especially cancers. Currently, the number of ideal clinical biomarkers is still limited partially because of lacking efficient methods in biomarker discovery. Nucleic acid aptamers are artificial single-stranded DNA or RNA sequences that can selectively bind to various targets with high specificity and affinity. Moreover, aptamers possess desirable advantages, including easy synthesis, convenient modification, relative chemical stability and low immunogenicity. Recently, different aptamer-based strategies have been developed to facilitate the discovery of biomarkers. Based on cell-SELEX technology, the selected aptamers can be used to identify cell-surface protein biomarkers of different cancer cells. SOMAscan can analyze thousands of proteins of different biological samples, which becomes a multiplexed protein biomarker discovery platform. Additionally, secreted protein biomarkers can be discovered by aptamers screened through secretome SELEX. In order to facilitate the identification of target proteins, several covalent cross-linking strategies have been developed, such as aptamer-based affinity labeling (ABAL), DNA-templated aptamer and protein-aptamer template (PAT). In this review, we mainly highlight the emerging nucleic acid aptamer-based biomarker discovery strategies and demonstrate their unique technological advantages in discovering cancer biomarkers. The challenges and perspectives of aptamer-based methods are also discussed.

Investigations on the interface of nucleic acid aptamers and binding targets.

Nucleic acid aptamers are single-stranded DNA or RNA of 20-100 nucleotides in length that have attracted substantial scientific interest due to their ability to specifically bind to target molecules via the formation of three-dimensional structures. Compared to traditional protein antibodies, aptamers have several advantages, such as their small size, high binding affinity, specificity, flexible structure, being chemical synthesizable and modifiable, good biocompatibility, high stability and low immunogenicity, which all contribute to their widely applications in the biomedical field. To date, much progress has been made in the study and applications of aptamers, however, detailed information on how aptamers bind to their targets is still scarce. Over the past few decades, many methods have been introduced to investigate the aptamer-target binding process, such as measuring the main kinetic or thermodynamic parameters, detecting the structural changes of the binding complexes, etc. Apart from traditional physicochemical methods, various types of molecular docking programs have been applied to simulate the aptamer-target interactions, while these simulations also have limitations. To facilitate the further research on the interactions, herein, we provide a brief review to illustrate the recent advances in the study of aptamer-target interactions. We summarize the binding targets of aptamers, such as small molecules, macromolecules, and even cells. Their binding constants (KD) are also summarized. Methods to probe the aptamer-target binding process, such as surface plasmon resonance (SPR), circular dichroism spectroscopy (CD), isothermal titration calorimetry (ITC), footprinting assay, truncation and mutation assay, nuclear magnetic resonance spectroscopy (NMR), X-ray crystallography and molecular docking simulation are indicated. The binding forces mediating the aptamer-target interactions, such as hydrogen bonding, electrostatic interaction, the hydrophobic effect, π-π stacking and van der Waals forces are summarized. The challenges and future perspectives are also discussed.

Synthesis and Anticancer Activity of 9-O-Pyrazole Alkyl Substituted Berberine Derivatives.

BACKGROUND: Berberine (BBR), an isoquinoline plant alkaloid isolated from plants such as Coptis chinensis and Hydrastis canadensis, own multiple pharmacological activities. OBJECTIVE: In this study, seven BBR derivatives were synthesized and their anticancer activity against HeLa cervical and A549 human lung cancer cell lines were evaluated in vitro. METHODS: The anti-cancer activity was measured by MTT assay, and apoptosis was demonstrated by the annexin V-FITC/PI staining assay. The intracellular oxidative stress was investigated through DCFH-DA assay. The molecular docking study was carried out in molecular operating environment (MOE). RESULTS: Compound B3 and B5 showed enhanced anti-cancer activity compared with BBR, the IC50 for compound B3 and B5 were significantly lower than BBR, and compound B3 at the concentration of 64 or 128 µM induced apoptosis in HeLa and A549 cell lines. The reactive oxygen species (ROS) was generated in both cell lines when treated with 100 µM of all the compounds, and compound B3 and B5 induced higher activity in the generation of ROS, while compound B3 exhibited the highest activity, these results are in accordance with the cytotoxicity results, indicating the cytotoxicity were mostly generated from the oxidative stress. In addition, molecular docking analysis showed that compound B3 had the greatest affinity with Hsp90. Upon binding, the protective function of Hsp90 was lost, which might explain its higher cytotoxicity from molecular interaction aspect. CONCLUSION: All the results demonstrated that compound B3 and B5 showed significantly higher anti-cancer ability than BBR, and compound B3 is a promising anticancer drug candidate.

Berberine Derivatives with Different Pharmacological Activities via Structural Modifications.

Berberine, a quaternary ammonium protoberberine alkaloid with an isoquinoline scaffold isolated from medicinal herbs, exhibits a wide spectrum of pharmacological activities. Berberine has been used in traditional Chinese medicine and Ayurvedic medicine. However, it has poor bioavailability, which seriously limits its application and development. The chemical transformation of natural products is an effective method to improve pharmacological activities. Researches have been carried out on the modification of berberine to obtain better pharmacological properties. In this paper, the structural modifications of berberine for different biological activities and its underlying mechanisms are reviewed.

Cefepime loaded O-carboxymethyl chitosan microspheres with sustained bactericidal activity and enhanced biocompatibility.

Cefepime (CFP) is a frequently used antibiotic for prevention of post-surgery infection. Systemic delivery of CFP in a bulk dose usually shows effective therapeutic effects, while cytotoxicity can also be generated. To avoid the drawback of systemic delivery of antibiotic, local and controlled administration of drug is being employed to prolong therapeutic effects and reduce cytotoxicity by sustaining drug release and minimizing drug exposure. In this work, CFP loaded polymer O-carboxymethyl chitosan (OCMC) microspheres (CFP-OCMC-MPs) were fabricated and their antimicrobial activity against Staphylococcus aureus as well as biocompatibility were evaluated. The microspheres possessed the spherical surface with diameter approximately 7 µm. Fourier transforms infrared spectral and wide-angle X-ray diffraction analysis showed that CFP was steadily incorporated. The drug loading content and encapsulation efficiency of the microspheres were 21.4 ± 0.5% and 42.3 ± 0.7%, respectively. The drug release profiles were found to be biphasic with an initial burst release followed by a gradual release phase, following the Higuchi model. In addition, the CFP-OCMC-MPs were able to kill all the bacteria cultured in suspension within 24 h and exhibited long-lasting bactericidal activity as demonstrated by inhibition zone study. Compared to CFP, CFP-OCMC-MPs showed a milder toxicity toward osteoblast-like cells over an 8 day period. All these results suggest that CFP-OCMC-MPs are endowed with sustained treatment of bacterial infection and enhanced biocompatibility.

Hydroxylation of multi-walled carbon nanotubes: Enhanced biocompatibility through reduction of oxidative stress initiated cell membrane damage, cell cycle arrestment and extrinsic apoptotic pathway.

Modification of CNTs with hydroxyl group promotes their applications in biomedical area. However, the impact of hydroxylation on their biocompatibility is far from being completely understood. In this study, we carried out a comprehensive evaluation of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) on the human normal liver L02 cell line, and compared it with that of pristine multi-walled carbon nanotubes (p-MWCNTs). Results demonstrated that compared with p-MWCNTs, MWCNTs-OH induced significantly lower oxidative stress as indicated by the level of intracellular antioxidant glutathione (GSH), subsequently lead to less cell membrane damage as demonstrated by lactate dehydrogenase (LDH) leakage assay, and showed slightly decreased arrestment of cell cycle distribution at G0/G1. More interestingly, MWCNTs-OH exhibited significantly lower tendency to activate caspase-8, a key molecule involved in the extrinsic apoptotic pathway. All these in vitro results demonstrated that hydroxylation of MWCNTs enhanced their biocompatibility compare with p-MWCNTs.

Synthesis and hypoglycemic activity of 9-O-(lipophilic group substituted) berberine derivatives.

A series of 9-O-(lipophilic group substituted) berberine derivatives were synthesized and evaluated for their cytotoxicity and hypoglycemic activity against HepG2 cells. All the results indicated that most of the synthesized compounds exhibited lower cytotoxicity and a certain degree of hypoglycemic activity. Especially the compounds 5g and 5h displayed dramatically increased hypoglycemic activity compared with berberine, and the cytotoxicity maintained or even lower than berberine, indicating that they are potential candidates for new anti-type 2 diabetes mellitus drugs.