Hydrogel is a kind of material with high water content,good biocompatibility and extracellular matrix-like property,among which polypyrrole(PPy)conductive hydrogels have both physical characteristics and excellent conductivity of hydrogels themselves.Its conductivity can be used to detect electrical signals generated in biological systems and provide electrical stimulation to regulate the activities and functions of cells and tissues.These characteristics make it widely used in the biomedical field.The recent progress of PPy conductive hydrogels in biomedical field was reviewed in this paper.In terms of classification,according to the cross-linking mechanism of PPy and hydrogel matrix,the non-covalent cross-linked PPy conductive hydrogels and covalent cross-linked PPy conductive hydrogels were divided.The applications of PPy conductive hydrogels in the biomedical field(Skin damage repair,nerve repair,myocardial repair and flexible sensing,etc.)were mainly introduced,and the development trend and challenges of PPy conductive hydrogels in the biomedical field were discussed.

Digital polymerase chain reaction(dPCR)is a PCR technology that realizes accurate quantification of single-copy nucleic acid molecules by dividing the reaction system into tens of thousands of independent PCR reaction units for single-molecule-level amplification and integrating Poisson distribution.Due to its single-copy sensitivity and accurate quantification without the need of standard curves,dPCR has been widely used in disease diagnosis.By introducing technologies such as stepped emulsification and three-dimensional imaging,dPCR has been greatly improved in terms of accuracy,multiplexability and turnaround time,significantly enhancing its performance in clinical disease diagnosis.Based on this,this paper traced the technological development history of dPCR,gave an overview of its application in detection of tumors,infections and other diseases,and further discussed the challenges and opportunities of the development of dPCR,with the aim of providing a reference for the development and utilization of dPCR in the future,and promoting the high-quality development of molecular technology in clinical testing.

The quality control of traditional Chinese medicine(TCM)is the core issue to ensure the modernization,industrialization and internationalization of TCM.Compared with other detection methods,electrochemical analysis method has many advantages such as high sensitivity,fast detection speed and low cost,making it an important means of quality control for TCM and having broad development prospects.This article reviewed the research progress of electrochemical methods in quality control of TCM in recent years,discussed the application of electrochemical fingerprinting technique in identification of TCM,and comprehensively summarized the application of electrochemical technology in analyzing effective components and harmful substances in TCM,including flavonoids,alkaloids,quinones,glycosides,heavy metals and pesticide residues.Finally,the development prospects of electrochemical methods in the field of quality control of TCM were discussed.

Fluorescence anisotropy(FA)analysis has many advantages such as no requirement of separation,high throughput and real-time detection,and thus has been widely used in many fields,including biochemical analysis,food safety detection,environmental monitoring,etc.However,due to the small volume or mass of the target,its combination with the fluorescence probe cannot produce significant signal change.To solve this issue,researchers often use nanomaterials to enhance the mass or volume of fluorophore to improve the sensitivity.Nevertheless,this FA amplification strategy also has some disadvantages.Firstly,nanomaterials are easy to quench fluorescence.As a result,the FA value is easily influenced by light scattering,which reduces the detection accuracy.Secondly,fluorescent probes in most methods require complex modification steps.Therefore,it is necessary to develop new FA probes that do not require the amplification of volume and mass or modification.As a new kind of nanomaterials,luminescent metal-organic framework(MOF)has a large volume(or mass)and strong fluorescence emission.It does not require additional signal amplification materials.As a consequence,it can be used as a potential FA probe.This study successfully synthesized a lanthanide metal organic framework(Ce-TCPP MOF)using cerium ion(Ce3+)as the central ion and 5,10,15,20-tetra(4-carboxylphenyl)porphyrin(H2TCPP)as the ligand through microwave assisted method,and used it as a novel unmodified FA probe to detect phosphate ions(Pi).In the absence of Pi,Ce-TCPP MOF had a significant FA value(r).After addition of Pi,Pi reacted with Ce3+in MOF and destroyed the structure of MOF into the small pieces,resulting in a decrease in r.The experimental results indicated that with the increase of Pi concentration,the change of the r of Ce-TCPP MOF(Δr)gradually increased.The Δr and Pi concentration showed a good linear relationship within the range of 0.5-3.5 μmol/L(0.016-0.108 mg/L).The limit of detection(LOD,3σ/k)was 0.41 μmol/L.The concentration of Pi in the Jialing River water detected by this method was about 0.078 mg/L,and the Pi value detected by ammonium molybdate spectrophotometry was about 0.080 mg/L.The two detection results were consistent with each other,and the detection results also meet the ClassⅡwater quality standard,proving that this method could be used for the detection of Pi in complex water bodies.

Lattice strain ruthenium nanoparticles uniformly and stably supported on nitrogen-modified carbon nanosheets(RuNPs/NC)were prepared via simple wet-chemical and subsequent pyrolysis method.The nitrogen doped NC could effectively improve their uniform dispersion and lattice compression of RuNPs.Through changing the pyrolysis temperature,the nitrogen content,types and degree of lattice strain of RuNPs could be effectively tuned,which could be used to adjust and control their peroxidase-like activity.The as-prepared RuNPs/NC-900 exhibited highest peroxidase-like activity,and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB)to produce a blue product with the maximum absorption at 652 nm in the presence of H2O2.The steady-state kinetic analysis indicated that the reaction catalyzed by RuNPs/NC followed the Michaelis-Menten kinetic model.Tannic acid(TA),gallic acid(GA)and ascorbic acid(AA)could effectively inhibit the RuNPs/NC-H2O2-triggered chromogenic reaction of TMB,resulting in color fading and decrease in absorbance.Based on this,a sensitive and accurate system was constructed for detection of TA,GA and AA.The detection limits(3σ/S)for TA,GA and AA were 0.014,0.014 and 0.29 μmol/L,respectively.This study not only developed a colorimetric sensing method based on RuNPs/NC nanozyme but also offered a new approach for the sensitive detection of antioxidants in food.

Band 3 protein is an important channel protein in the erythrocyte membrane which mediates the anion transport process inside and outside the cell membrane,as well as contributes to the maintenance of erythrocyte morphology,and has important physiological functions.However,the distribution state of this protein in the primary cell membrane is not known.Cryo-scanning electron microscopy enables imaging of the surface morphology of biological samples in a near-physiological state.In order to investigate the distribution of band 3 protein on erythrocyte membranes under physiological conditions,the present study utilized 5-nm gold nanoparticles modified with the antibodies to specifically bind to the band 3 protein on human blood erythrocyte membranes and imaged them by cryo-scanning electron microscopy,to obtain distribution of band 3 protein on human blood erythrocyte membranes.The results showed that the membrane proteins on the erythrocyte membranes tended to be clustered and distributed to form ″protein islands″,and band 3 proteins were mainly distributed in these protein islands,which were tightly connected with each other to form several functional microregions to play their respective roles.

A polymethionine(p-Met)-modified laser-induced graphene(LIG)electrode was constructed and integrated with portable electrochemical workstations and handheld computer to achieve on-site,simultaneous detection of azo dyes sunset yellow(SY)and tartrazine(Tz)in environmental water.Firstly,the sensor interface with the best electrical conductivity was obtained by optimizing the laser processing parameters,and then the electrochemical responses of SY and Tz were improved by electropolymerization of methionine on the surface of LIG.Finally,a portable electrochemical sensor platform was built by connecting p-Met/LIG,a small electrochemical workstation and a handheld computer application program.Differential pulse voltammetry(DPV)was used to determine these two dyes.SY showed a good linear relationship in the concentration range of 0.2-20 μmol/L and 20-100 μmol/L,the detection limit was as low as 0.001 μmol/L.Tz showed a good linear relationship in concentration range of 0.3-40 μmol/L and 40-100 μmol/L,and the detection limits was as low as 0.005 μmol/L.p-Met/LIG also had excellent anti-interference performance and reproducibility.The portable electrochemical platform was applied to real-time detection of real water samples,and the results showed that the platform was expected to be applied in field detection of SY and Tz in real environmental water bodies.

Human exhaled breath has great application prospects,e.g.,monitoring pharmacokinetics,disease diagnosis,due to its advantages such as non-invasive and high-frequency sampling.Breath samples can be collected from the oral and nasal cavity.However,the oral and nasal environment affect the chemical composition of breath sample.Therefore,the investigation on the chemical composition of mouth-exhaled breath and nose-exhaled breath is crucial for selection of appropriate sampling strategy for individual studies.In this work,secondary electrospray ionization-high resolution mass spectrometry(SESI-HRMS)was applied to analysis of respiratory metabolomics in real time.A quantitative analysis approach was established for 9 kinds of volatile organic compounds(VOCs)e.g.2-butanone,2-pentanone,ethyl acetate,methyl methacrylate,toluene,styrene,mesitylene,isoprene and limonene.The limit of detection was 2.3?240.8 ng/m3.The intra-day(n=6)and inter-day(n=18)relative standard deviations were 0.6%?4.6%and 4.3%?12.2%,respectively.Nine healthy subjects were recruited to investigate the chemical composition of mouth-exhaled and nose-exhaled breath.The results showed the good performance in quantitative analysis of 9 VOCs in breath air.It was found that the number of unique component(m/z)detected in mouth-exhaled breath(167)was 2.2 times greater than that detected in nose-exhaled breath(76),which might result from the complex environment in oral cavity.The signal intensity of commun component(163)was significantly different between mouth-exhaled breath and nose-exhaled breath.Additionally,the elemental composition analysis showed that the proportion of polar compounds detected in nose-exhaled breath was higher than that in mouth-exhaled breath.This study demonstrated that there was significant differences in the chemical composition between mouth-exhaled and nose-exhaled breath,which provided a theoretical basis for selection of exhalation mode.

The molecularly imprinted polymers membranes(MIPMs)were prepared for selective adsorption of lamotrigine(LTG)in plasma by surface molecular imprinting technology with polyvinylidenefluoride(PVDF)membranes as supporter,lamotrigine as template molecule,methyl methacrylate as functional monomer,ethylene glycol dimethacrylate as cross-linking agent,azodiisobutyronitrile as initiator and acetonitrile-dimethylformamide(1∶1.5,V/V)as pore-forming agent.The prepared MIPMs were characterized by scanning electron microscope,Fourier transform infrared spectroscopy,Brunaner-emmet-teller measurements,X-ray photoelectron spectroscopy,and thermogravimetric analysis.The adsorption properties of the materials were investigated by kinetic adsorption,isothermal adsorption,selective adsorption,adsorption-desorption and reusability experiments.The results showed that the imprinted layer of LTG was successfully coated on the surface of PVDF,and the materials had uniform particle size.The adsorption capacity and imprinting factor of the MIPMs towards LTG were 3.77 mg/g and 8.97,respectively.The nanomaterials showed fast mass transfer rate(30 min)and good reusability(the adsorption efficiency was 86.66%after 6 cycles),and could be used for the adsorption of LTG in plasma with low matrix interference,recoveries of 86.54%-90.48%and RSD of 1.51%-3.15%(n=5).The proposed LTG MIPMs were demonstrated to be simple and environment friendly,and had high selectivity in rapid separation and extraction of LTG in plasma.

Projection micro stereolithography three-dimensional(3D)printing method was proposed in this study to fabricate complex microchannels of combined cross-sections.By using 3D printing and polydimethylsiloxane(PDMS)replication methods,two inertial microfluidic chips of three-step and five-step cross-sections were fabricated,and the dimension precisions of the microchannels were controlled within 20 μm.Using the microfluidic chips,the movements of two fluorescent polystyrene particles with diameters of 10 and 6 μm in the stepped channels were investigated.In addition,numerical simulations were applied to demonstrate the inertial focusing mechanisms of particles in the channels.It was found that 10-μm particles had three equilibrium positions in the three-step channel,which located at the inner walls of the three steps,respectively,and most particles focused at the inner step.The 6-μm particles also had three equilibrium positions in the three-step channel.However,the particles migrated to the middle and the outer steps under high flow rates.In the five-step channel,when the flow rate was increased gradually,10-μm particles had a single and two equilibrium positions,respectively,and the particles migrated towards the inner channel wall under high flow rates.In comparison to 10-μm particles,6-μm particles had two stable equilibrium positions in the five-step channel at all flow rate range.It could be concluded that the quantity,shape and strength of the secondary flow vortex could be altered by changing structure of the combined cross-section,thus the equilibrium positions and quantities of the focusing particles could be also regulated.The research outcome might provide new insights for precise cell inertial manipulation and promote the application and development of inertial microfluidic technology in biomedical and other fields.