An injectable smart nanofiber-based intravascular site-specific sensing system and a preparation and application method thereof

Abstract

The application discloses an injectable intelligent nanofiber intravascular fixed-point sensing system and belongs to the technical field of nanomedical treatment. The system comprises an injectable composite nanofiber main body, which is integrated with an in-vivo energy collection module, an on-chip sensing module, an on-chip threshold detection module and a passive near-field coupling response unit. The on-chip threshold detection module adopts a sub-threshold comparator based on an organic electrochemical transistor, and all preparation processes can be completed at a temperature lower than 40 DEG C. After the fiber is injected into a blood vessel, the fiber is fixed at a lesion area by using a surface targeting ligand, and the fiber continuously monitors biochemical parameters such as proteins, enzymes and ions in situ by using blood vessel pulsatile pressure power supply. The on-chip threshold detection module performs local threshold discrimination, and only changes the resonance state of the passive GHz resonance response unit when a pathological abnormality is identified, so that an external receiver can be scanned and detected. The application further discloses a preparation method and an application method of the system. The system realizes "unmanned" blood vessel health guarding without external continuous power supply, and is suitable for early warning and long-term monitoring of cardiovascular diseases such as atherosclerosis.

Description

Technical Field

[0001] This invention relates to endovascular interventional diagnosis and treatment and micro / nano sensing technology, specifically to an injectable smart nanofiber that integrates in vivo energy harvesting and passive response communication, and its application in intravascular fixed-point real-time multi-parameter sensing and diagnosis. Background Technology

[0002] Digital subtraction angiography (DSA) remains the gold standard for diagnosing cardiovascular diseases such as atherosclerosis and vasculitis. However, DSA is an invasive and incidental examination that only provides static morphological images of the blood vessel lumen. It cannot capture the dynamic evolution of molecular lesions within the vessel wall, nor can it continuously monitor the risk of high-risk plaque rupture. Furthermore, DSA examinations carry risks of ionizing radiation exposure and contrast agent nephrotoxicity, making it unsuitable as a long-term monitoring method for chronic vascular diseases.

[0003] In the field of molecular imaging, nanoparticle contrast agents have been widely studied for enhancing imaging contrast. However, these contrast agents only passively enhance imaging signals and do not possess active sensing capabilities. They cannot distinguish between physiological molecular fluctuations and pathological abnormalities, nor can they provide quantitative biochemical indicators.

[0004] Significant progress has been made in implantable biosensor technology in recent years. However, most existing implantable sensors rely on built-in batteries or percutaneous leads for power, with limited battery life and replacement requiring a second surgery. While wireless sensors eliminate the need for wires, they still require an external transmitting coil for continuous power, preventing true in vivo autonomy. Furthermore, existing implantable sensors are mostly in the millimeter to centimeter range in size, requiring surgical implantation and cannot be delivered via minimally invasive injection.

[0005] In the field of energy harvesting, piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) have been shown to convert biomechanical energy into electrical energy. However, most existing implantable nanogenerators are designed as macroscopic (centimeter-scale) pacemaker power devices or extravascular patches, whose size and rigidity make them impossible to deliver by injection, let alone reside in blood vessels at a fixed point and interact with the microenvironment at the molecular level.

[0006] In the field of low-power circuits, transistors operating in the subthreshold region have been shown to achieve basic amplification and comparison functions at extremely low voltages (<200 mV) and extremely low power consumption (pW to nW). However, existing subthreshold circuits are all based on planar chips of silicon-based semiconductors, and their fabrication relies on high-temperature (>800°C) processes. This makes it impossible to heterogeneously integrate them with polymer nanofibers and bioactive molecules at low temperatures, thus preventing the formation of practical integrated systems with injectable fiber carriers and in vivo energy harvesting modules.

[0007] In the field of passive wireless communication, passive radio frequency identification (RFID) tags based on LC resonant circuits have been widely used for asset tracking and biosensing. However, existing passive LC resonant tags are mostly in the millimeter to centimeter range in size, and their operating frequencies are mostly designed to be low (<100 MHz) to match macroscopic inductance and capacitance parameters. They have not been combined with injectable nanofibers and intravascular targeted residence technologies, nor have they worked in conjunction with ultra-low power threshold discrimination systems based on organic electrochemical transistors.

[0008] In the field of targeted delivery, ligand-modified nanoparticles and nanofibers have been used to target atherosclerotic plaques. For example, nanocarriers targeting vascular cell adhesion molecule-1 (VCAM-1) or collagen exposed on the basement membrane can accumulate in plaque regions. However, these carriers are only used for drug delivery and do not integrate energy harvesting, threshold detection, and passive response communication functions.

[0009] In summary, the existing technology has the following core technical defects: (1) It lacks an integrated intravascular sensing system that can simultaneously achieve injectability, targeted residence, in vivo energy autonomy, local threshold discrimination and passive response communication; (2) It lacks a low-temperature manufacturing process that heterogeneously integrates energy harvesting, ultra-low power threshold detection and multi-target biochemical sensing into a single submicron to micron-scale fiber, especially lacking non-silicon-based transistor technology that can be integrated with polymer fibers at temperatures below 40°C; (3) It lacks an energy architecture that can achieve in vitro information reading through passive resonant response under the constraint of low-quality energy such as vascular pulsation pressure, especially lacking a GHz-band LC resonant design that is self-consistent with the geometry of micron-scale fibers.

[0010] The present invention aims to solve all the above-mentioned technical problems. Summary of the Invention

[0011] The core of this invention lies in providing a fully biocompatible composite functional nanofiber system that can be injected through conventional injection needles. This system does not rely on external energy or toxic fuels, but instead innovatively integrates a smart materials platform, in vivo energy autonomy, ultra-low power threshold discrimination based on organic electrochemical transistors, and a passive GHz resonant response.

[0012] Specifically, the present invention provides the following technical solutions:

[0013] Technical Solution 1: Injectable Intelligent Nanofiber Intravascular Point Sensing System

[0014] An injectable intelligent nanofiber intravascular pinpoint sensing system comprises one or more injectable, biocompatible composite nanofibers. The composite nanofibers have a diameter of 100 nanometers to 50 micrometers and a length of 200 micrometers to 500 micrometers. This size range ensures that the fibers have sufficient specific surface area to integrate functional modules while allowing for smooth injection through standard 25G to 32G needles. The lower length limit of 200 micrometers provides the necessary winding space for the inductor coil in the passive near-field coupling response unit, while ensuring the geometric feasibility of the inductance and capacitance required by the LC resonant circuit in the GHz band. The upper length limit of 500 micrometers provides sufficient electrode spacing and inductor turns for near-field coupling, while avoiding excessive length that could lead to injection blockage or blood flow disturbance.

[0015] The composite nanofiber body integrates an in vivo energy harvesting module, at least one on-chip sensing module, an on-chip threshold detection module, and a passive near-field coupling response unit.

[0016] The in vivo energy harvesting module is configured to convert the mechanical energy generated by vascular pulsation pressure into electrical energy. In a preferred embodiment of the invention, the module is a micro piezoelectric-triboelectric composite nanogenerator based on a fiber structure, arranged along the fiber axis. The minute periodic deformation (frequency 0.1-5 Hz, strain 0.1%-2%) generated by vascular pulsation pressure causes polarization or charge separation of the piezoelectric and triboelectric layers, thereby generating alternating current output. After rectification and charge accumulation, this electrical energy directly drives an on-chip threshold detection module and an on-chip sensing module with matching operating voltage.

[0017] The on-chip sensing module is configured to detect at least one biochemical parameter in the vascular microenvironment. Sensing units include, but are not limited to: pH-sensitive electrodes, enzyme-modified electrodes (such as matrix metalloproteinase-9 responsive electrodes), and ion-selective electrodes (such as…). , The sensor also includes a protein recognition electrode based on DNA aptamers. The sensing signal is transmitted to the on-chip threshold detection module via the conductive polymer core.

[0018] The on-chip threshold detection module is configured to receive signals collected by the on-chip sensing module, perform local threshold comparison, and output a trigger signal to change the response state of the passive near-field coupling response unit when the detection signal exceeds a predetermined threshold.

[0019] In a key embodiment of the present invention, the on-chip threshold detection module is an analog comparator operating in the subthreshold region based on an organic electrochemical transistor (OECT). The channel layer of the OECT is composed of a conductive polymer (such as poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or poly(3-hexylthiophene) (P3HT)), the source and drain electrodes are composed of inkjet-printed conductive polymers or metal nanowires, and the gate electrolyte is a composite ion gel of a fluorinated ionic liquid and a polymer matrix. This OECT can achieve high-gain analog comparator functionality at an operating voltage below 100 mV, its subthreshold region standby power consumption can be as low as sub-pW, and the entire fabrication process can be completed at a low temperature below 40°C, fundamentally solving the incompatibility problem between the high-temperature process of silicon-based transistors and the activity of biomolecules.

[0020] The on-chip threshold detection module includes a single-transistor comparator or a dual-transistor differential pair comparator based on an organic electrochemical transistor, and a reference voltage generation unit coupled to the comparator. The reference voltage is provided by a silver / silver chloride microelectrode or a voltage divider resistor network integrated on the fiber, corresponding to a pre-stored pathological threshold. The comparator is configured to receive an analog signal from the on-chip sensing module and compare it with the reference voltage; the circuit outputs the trigger signal only when the analog signal exceeds the threshold corresponding to the reference voltage.

[0021] In another embodiment of the invention, the on-chip threshold detection module is an ultra-low power analog threshold discrimination unit based on organic electrochemical transistors, on which preset threshold parameters are embedded. This threshold discrimination unit is configured to: continuously monitor the raw signal from the sensing module locally, perform signal amplification and threshold discrimination, and distinguish between physiological fluctuations and pathological abnormal signals. Only when a pathological signal exceeding a predetermined risk threshold is detected is the trigger signal output to change the response state of the passive near-field coupling response unit, thereby transmitting an encoded response containing diagnostic information to the external receiver.

[0022] The threshold parameters employ an online adaptive adjustment mechanism. This mechanism continuously fine-tunes the judgment threshold using locally collected data, eliminating the need to transmit raw sensor data or model parameters to an external server. This avoids communication overhead and privacy risks, enabling personalized monitoring.

[0023] The passive near-field coupling response unit is configured to generate a characteristic resonant signal in response to an external scanning electromagnetic field, and its resonant characteristics change detectably in response to the trigger signal. In a preferred embodiment of the invention, the passive near-field coupling response unit is an LC resonant circuit integrated on the composite nanofiber body, comprising an inductive element composed of helical metal nanowires deposited on or inside the fiber surface, and a capacitive element composed of metal electrodes segmentally deposited at both ends or on the surface of the fiber. The pitch of the helical metal nanowires is 200 nm to 2 μm, and the linewidth is 50 nm to 500 nm; the capacitance of the capacitive element is 0.1 picofarads to 1 picofarad. Based on the above geometric parameters, the resonant frequency of the LC resonant circuit is in the range of 0.5 GHz to 6 GHz, which is physically consistent with the size of the micron-scale fiber. The resonant frequency of the LC resonant circuit shifts in response to the trigger signal, and the external receiver reads the diagnostic information by detecting the shift in the resonant frequency. The passive near-field coupling response unit does not require active transmission power; its energy comes from the external scanning electromagnetic field.

[0024] Since the passive resonant response does not consume the energy collected within the body, the external receiver can actively scan when data needs to be read, and the fiber does not need to maintain communication power consumption under normal circumstances, thereby reducing the system energy consumption to the theoretical limit.

[0025] The outer shell of the composite nanofiber matrix is ​​a biocompatible hydrogel or a cell membrane-like coating, which is modified with targeting ligands (such as antibody fragments targeting VCAM-1, peptide sequences targeting exposed collagen, or peptides targeting fibrin). This outer shell is used to specifically bind to target vascular endothelial cells or diseased tissue, achieving site-specific residence.

[0026] Technical Solution 2: Multi-layer Coaxial Structure

[0027] The composite nanofiber body has a multi-layered coaxial structure, comprising, from the inside out:

[0028] Core layer: made of conductive polymer nanofibers (such as poly(3-hexylthiophene) or polyaniline nanofibers), serving as a signal transmission bus to connect the electrodes of the sensing module, threshold detection module and energy harvesting module.

[0029] Intermediate functional layer: Contains the in vivo energy harvesting module, on-chip sensing module, and on-chip threshold detection module. This layer integrates piezoelectric / triboelectric materials, sensing electrodes, and organic electrochemical transistors into specific regions along the fiber's radial direction using coaxial electrospinning or microfluidic wet spinning techniques.

[0030] The outer shell is a biocompatible hydrogel (such as methacrylamide gelatin) or a cell membrane-like coating (such as a phospholipid bilayer modified polymer) on which a targeting ligand is chemically coupled.

[0031] Technical Solution 3: Preparation Method

[0032] A method for preparing the above system, the key steps of which include:

[0033] (1) Multilayer nanofibers were continuously drawn using coaxial electrospinning or microfluidic wet spinning technology at an ambient temperature below 40 degrees Celsius. A conductive polymer solution was pumped into the core layer; a mixed solution of piezoelectric copolymer (such as polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE)) and zinc oxide nanowires was pumped into the middle layer; and a methacrylamide gelatin hydrogel precursor was pumped into the outer shell layer.

[0034] (2) During or after the fiber drawing process, sensing electrodes, piezoelectric layers, and organic electrochemical transistors are sequentially deposited in the middle section of the fiber using in-situ inkjet printing, photolithography, or electron beam direct writing technology. The organic electrochemical transistors are formed by inkjet printing of a conductive polymer channel layer, source / drain electrodes, and an ion-gel gate electrolyte, with the entire process occurring at temperatures below 40 degrees Celsius. For fiber segments with a diameter greater than 5 micrometers, photolithography can be used; for fiber segments with a diameter of 1-5 micrometers, electron beam direct writing technology can be used to achieve sub-micrometer precision patterning.

[0035] (3) Depositing helical metal nanowires on or inside the fiber to form an inductive element, and depositing metal electrodes in segments at both ends or on the surface of the fiber to form a capacitive element, thus constituting the passive near-field coupling response unit. The helical metal nanowires can be achieved by tilted-angle electron beam evaporation or inkjet printing of high-concentration metal nanowire ink.

[0036] (4) Modify the biocompatible shell and targeting ligand using layer-by-layer self-assembly technology. The fiber is immersed in polycationic and polyanionic electrolyte solutions and deposited alternately to form a cell membrane-like outer layer; then immersed in phosphate buffer (pH 7.4) containing the targeting peptide (such as cRGD peptide) and incubated at 4°C for 12 hours to complete the targeting modification.

[0037] (5) The steps involving biological functional molecules in the entire preparation process are carried out under sterile conditions and below 40 degrees Celsius to ensure the activity of biological functional molecules (such as enzymes and DNA aptamers).

[0038] Technical Solution 4: Intravascular Targeted Diagnostic Method

[0039] A method for intravascular pinpoint diagnosis using the above system includes the following steps:

[0040] (1) A saline suspension containing the intelligent nanofibers is injected into a blood vessel through a standard peripheral venous catheter or arterial sheath. The fibers remain monodisperse in the injection fluid, avoiding aggregation and clogging of the needle.

[0041] (2) The nanofibers circulate with the blood flow and, through surface targeting modification, autonomously locate themselves in predetermined vascular lesion areas (such as the shoulder of coronary atherosclerotic plaques, the bifurcation of the carotid artery, etc.). The targeting mechanisms include: passive targeting (utilizing the effect of increased interstitial space within the plaque area), active targeting (ligand-receptor specific binding), and hemodynamic assistance (utilizing the eddies and low-velocity areas at the bifurcation to increase the probability of fiber-vascular wall contact).

[0042] (3) After the nanofibers are deposited, the system is powered on using the energy of the blood vessel's own pulsating pressure, which starts the on-chip threshold detection module and begins continuous, non-invasive, in-situ monitoring of various protein, enzyme, and ion indicators. The system adopts an event-driven architecture and is normally in an ultra-low power sleep state, with the energy harvesting module supplying power only to the bias circuit of the sensing module and the standby circuit of the threshold detection module.

[0043] (4) The on-chip threshold detection module only changes the resonant state of the passive near-field coupling response unit when it detects preset pathological thresholds such as plaque instability or increased risk of rupture. The in vitro receiver obtains clinical graded alarms by actively scanning and detecting changes in the resonant state. Pathological thresholds include, but are not limited to, combinations of parameters such as: continuously increasing MMP-9 concentration, decreasing pH value (acidic microenvironment), increased reactive oxygen species (ROS) level, and abnormal fluctuations in calcium ion concentration.

[0044] (5) This enables “unmanned” vascular health monitoring that does not require continuous power supply or monitoring from external devices. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the multilayer coaxial structure of the smart nanofiber of the present invention, showing the core wire, piezoelectric layer, threshold detection layer based on organic electrochemical transistor, sensing layer, GHz band LC resonant response unit and target shell.

[0046] Figure 2 This is a computer fluid dynamics simulation diagram showing the entire process of fibers moving within blood vessels under the influence of blood flow and pulsation, from free flow and tumbling towards the vessel wall to attachment and residence.

[0047] Figure 3 The logic block diagram for sparse data stream processing of the on-chip threshold detection module is as follows: Sensor array data → Local threshold comparison → Trigger resonance state change / maintain original state.

[0048] Figure 4 The working principle diagram of the passive LC resonant response unit is as follows: the external scanning coil generates an alternating electromagnetic field in the GHz band, the LC circuit on the fiber generates a resonant response, and the threshold detection module modulates the resonant frequency by changing the capacitance or inductance value through an organic electrochemical transistor switch.

[0049] Figure 5This is a timing diagram of the energy management unit of the present invention, showing the timing relationship between energy accumulation, intermittent threshold detection and passive resonant response.

[0050] Figure Labels

[0051] 1. Composite nanofiber matrix; 2. Core layer (conductive polymer nanofibers); 3. Intermediate functional layer; 4. Outer shell layer (biocompatible hydrogel); 5. Targeting ligand; 6. In vivo energy harvesting module; 7. On-chip sensing module;

[0052] 8 On-chip threshold detection module (OECT); 9 Passive near-field coupling response unit (LC resonant circuit);

[0053] 10 Inductive element (spiral metal nanowire); 11 Capacitive element; 12 Conductive polymer channel layer; 13 Ion gel gate electrolyte; 14 Source / drain electrode; 15 Reference voltage generation unit; 16 External scanning coil; 17 Blood flow direction; 18 Blood vessel wall / endothelial cells; 19 Lesion tissue / atherosclerotic plaque; 20 Blood flow eddy region; 21 Sensor array; 22 Trigger signal; 23 Resonance state change / maintenance; 24 Parallel capacitor path; 25 Alternating electromagnetic field; 26 Resonant frequency (normal state) ); 27 resonant frequency (trigger state) ); 28 Vascular pulsation pressure; 29 Energy harvesting output; 30 Capacitor voltage; 31 Detection trigger pulse; 32 Resonance state switching signal; 33 Energy accumulation stage; 34 Intermittent threshold detection window; 35 Passive resonance response stage; 36 Dormant period; 37 Active period; 38 Free flow dynamics; 39 Tumbling approach state; 40 Wall-attached dwelling state; 41 Physiological fluctuation signal; 42 Pathological abnormal signal; 43 Threshold discrimination unit. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0055] Example 1: Preparation of core composite nanofibers

[0056] A three-layer coaxial nozzle electrospinning device was used. The core layer was pumped with an 8 wt% poly(3-hexylthiophene) (P3HT) chloroform solution at a flow rate of 0.5 mL / h; the middle layer was pumped with a 15 wt% N,N-dimethylformamide / acetone mixed solution (volume ratio 7:3) of polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE), molar ratio 70:30) and zinc oxide nanowires (5% by mass) at a flow rate of 1.0 mL / h; and the outer shell layer was pumped with a 10 wt% aqueous solution of methacrylamide gelatin (GelMA) (containing 0.5 wt% photoinitiator I2959) at a flow rate of 0.8 mL / h.

[0057] Spinning parameters: voltage 15 kV, receiving distance 15 cm, inner needle diameter of nozzle 0.4 mm, outer needle diameter 1.2 mm, ambient temperature 25℃, relative humidity 45%.

[0058] During the spinning process, a programmable pulsed laser beam (wavelength 355 nm, pulse width 10 ns, repetition frequency 1 kHz) is used to etch trenches approximately 50 nm deep and 200 nm wide in predetermined sections of the fiber to increase the adhesion of subsequent functional layers. Subsequently, using an in-situ inkjet printing system (printer orifice diameter 20 μm), the following are sequentially deposited in the trench region: a gold electrode (thickness 30 nm, serving as both a sensing electrode and a rectifier electrode), a PEDOT:PSS-based organic electrochemical transistor channel layer (thickness 100 nm, channel length 500 nm, width 2 μm), and a silver / silver chloride reference electrode (thickness 50 nm).

[0059] The gate electrolyte of the organic electrochemical transistor is deposited by inkjet printing. The composition is an ion gel composed of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]) and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) in a mass ratio of 4:6, with a thickness of about 5 μm. After printing, it is vacuum dried and cured at 25°C.

[0060] An inductor element is formed by depositing a spiral gold wire with a thickness of 50 nm, a width of 200 nm, and a pitch of 500 nm on the surface of a fiber using tilted-angle electron beam evaporation (tilt angle 60°, spin deposition). Gold electrode pads with an area of ​​5 μm × 5 μm are deposited at both ends of the fiber and connected to the ends of the spiral gold wire, forming the capacitor element of an LC resonant circuit. The spiral gold wire forms approximately 700 turns on a 350 μm long fiber, and the inductance is verified to be approximately 15 nH through electromagnetic simulation. The two electrodes form a capacitance of approximately 0.35 pF in the fiber dielectric (equivalent dielectric constant approximately 4). The resonant frequency is calculated to be f = 1 / (2π√(15 nH × 0.35pF)) ≈ 2.2 GHz, located in the ISM band.

[0061] After spinning, the fibers were collected in deionized water and ultrasonically sheared (50 W, 30 s) to obtain monodisperse short fibers with a length of 200-500 μm. Subsequently, the fibers were immersed in a 0.1 mg / mL polylysine solution for 10 minutes, followed by an immersion in a 0.1 mg / mL polyglutamic acid solution for 10 minutes, repeated three times to form a layer-by-layer assembly mimicking the outer membrane of a cell. Finally, the fibers were immersed in phosphate buffer (pH 7.4) containing 1 mM cRGD peptide and incubated at 4°C for 12 hours to complete the targeted modification.

[0062] The obtained fibers were characterized by scanning electron microscopy (SEM), with a diameter of 2.0 ± 0.5 μm and a length of 350 ± 100 μm. Fluorescence microscopy revealed that the cRGD peptides were uniformly distributed on the fiber surface.

[0063] Example 2: Validation of in vivo energy harvesting and design of energy management

[0064] The fibers obtained in Example 1 were fixed on the fixture of a micro mechanical testing instrument (Instron 5944), and cyclic stretching with a frequency of 1.5 Hz and a strain of 0.5% was applied to simulate the pulsation of the human carotid artery (the radial strain of the blood vessel wall corresponding to a systolic blood pressure of 120 mmHg and a diastolic blood pressure of 80 mmHg is about 0.3%-0.8%).

[0065] The electrical output characteristics of the fiber were measured using a source meter (Keithley 2450) with integrated gold electrodes. The open-circuit voltage was approximately 100 millivolts, and the short-circuit current was approximately 1.0 nanoamp.

[0066] Energy budget theory analysis: Considering the effective energy harvesting of the AC waveform after full-wave rectification of the piezoelectric-triboelectric composite output at a 1.5 Hz pulsation frequency, the energy harvested per cycle is estimated as follows: E_cycle = η × V_oc × I_sc × (1 / f) × k where η is the rectification efficiency (taken as 0.6) and k is the waveform correction factor (taken as 0.2). E_cycle ≈ 0.6 × 100 mV × 1.0 nA × 0.67 s × 0.2 ≈ 8.0 pJ.

[0067] The average power output is: P_avg = E_cycle × f = 8.0 pJ × 1.5 Hz ≈ 12 pW.

[0068] This invention achieves system self-sufficiency through the following energy management strategy:

[0069] (1) Working voltage matching design: The on-chip threshold detection module adopts an organic electrochemical transistor subthreshold comparator, whose working voltage is directly matched with the piezoelectric output voltage (100 mV), eliminating the need for a boost converter and eliminating the static power consumption overhead of the boost circuit.

[0070] (2) Deep sleep mechanism: The ion leakage current of the organic electrochemical transistor can be as low as 50 fA under zero gate bias or subthreshold gate voltage, and the standby power consumption is designed to be less than 1 pW. The bias circuit of the sensing module adopts a high-resistivity design (bias resistor > 100 GΩ), and the static power consumption is less than 0.5 pW.

[0071] (3) Energy accumulation mechanism: A 10 nF miniature capacitor is used as the energy storage unit. The estimated time required for the capacitor to charge from 0V to 100 mV under a 1.5 Hz pulsation is: t_charge = (C × ) / (2 × P_avg) = (10 × F × (0.1 V)²) / (2 × 12 × W) ≈ 4.2 seconds.

[0072] (4) Intermittent operating mode: After the capacitor is fully charged, the system enters the active period. During this period, the on-chip threshold detection module performs a complete signal acquisition-comparison process (the gate charging and comparison of the organic electrochemical transistor consumes approximately 5 pJ of energy). If no abnormality is detected, it returns to sleep mode; if an abnormality is detected, it outputs a trigger signal to change the capacitance value of the LC resonant circuit (by controlling the parallel capacitor path through the organic electrochemical transistor switch, consuming approximately 2 pJ of energy). Since the passive resonant response does not consume internal energy, the change in resonant frequency can be maintained once it is completed until the next threshold detection.

[0073] (5) Adaptive sampling: The on-chip threshold detection module dynamically adjusts the sampling frequency according to the capacitor voltage level. When the energy is sufficient, the sampling interval is 10 minutes; when the energy is insufficient, it is automatically extended to 30 minutes or 1 hour.

[0074] The energy management design described above ensures that the system can maintain long-term autonomous operation with a sufficient energy surplus at an average power input of 12 pW.

[0075] Example 3: Design and Verification of Multi-Target Sensing and On-Chip Threshold Detection Functions

[0076] A microenvironment model of vascular plaques was established within a polydimethylsiloxane (PDMS) microfluidic chip. The chip channel dimensions were 500 μm (width) × 100 μm (height) × 20 mm (length), and the bottom surface was coated with type I collagen (simulating the basement membrane exposed at the shoulder of the plaque).

[0077] Macrophages containing stable expression of matrix metalloproteinase-9 (MMP-9) (density 10⁻⁶) were injected into the chip channel. 6 The culture medium, containing 50 μg / mL of oxidized low-density lipoprotein (ox-LDL) and 50 μg / mL, was prepared at a flow rate of 0.5 mL / min (simulating arterial blood flow shear stress of approximately 20 dyn / cm²). After 24 hours of incubation, a simulated plaque microenvironment was formed.

[0078] Subsequently, the smart fiber obtained in Example 1 (concentration 10) 5(1 fiber / mL) is injected into the chip inlet. The fibers circulate with the liquid flow and are expected to adhere to the collagen-coated chip bottom surface within 10 minutes.

[0079] After the fiber is deposited, the on-chip threshold detection module automatically starts a work cycle every 10 minutes:

[0080] (1) pH detection: Open circuit potential shift was measured by gold electrode. In the simulated acidic microenvironment of plaque (pH 6.8), the potential shift was predicted to be approximately -35 mV (relative to the pH 7.4 control group) according to the Nernst equation theory.

[0081] (2) MMP-9 detection: The change of the characteristic peak at 100 Hz was measured by AC impedance spectroscopy. The MMP-9 enzyme digestion of the DNA aptamer probe caused a change in the charge density on the electrode surface, resulting in a theoretical change of about 10-20% in the impedance modulus.

[0082] (3) On-chip threshold discrimination: The organic electrochemical transistor comparator compares the sensing signal with the reference voltage. The reference voltage corresponds to the preset "high-risk plaque" threshold: MMP-9 impedance change rate > 10% / h and pH offset < -30 mV.

[0083] (4) Passive resonant response: When the signal is determined to be "high risk", the comparator outputs a trigger signal, which closes a parallel capacitor path (parallel capacitor of about 0.1 pF) through the organic electrochemical transistor switch, changing the total capacitance value of the LC resonant circuit, thereby shifting the resonant frequency downward from 2.2 GHz by about 300 MHz. The external receiver detects this frequency shift through a scanning coil.

[0084] Control experiment design: Unmodified cRGD peptide fibers were injected into the same chip. It was expected that only random, non-specific fiber attachment would be observed, and no directional resonant frequency change would be triggered, thus demonstrating the necessity of targeted modification.

[0085] Example 4: Performance Design Verification of Passive Near-Field Coupled Response Unit

[0086] The fiber obtained in Example 1 was placed in simulated body fluid (SBF, pH 7.4, 37°C), and the resonance characteristics of the LC resonant circuit were measured by connecting an in vitro scanning coil (5 mm in diameter, 1 mm apart from the fiber) to a vector network analyzer.

[0087] Design parameter verification: The inductance of the spiral gold wire, after electromagnetic simulation and equivalent circuit fitting, is approximately 15 nH, and the capacitance at both electrodes is approximately 0.35 pF. The measured resonant frequency is in the range of 2.1-2.3 GHz, consistent with the theoretical calculation. When the on-chip threshold detection module triggers the parallel capacitor switch, the total capacitance increases to approximately 0.45 pF, and the measured resonant frequency shifts downward to approximately 1.9 GHz, a frequency shift of approximately 400 MHz. The external receiver can clearly distinguish this frequency using a standard microwave frequency band detection algorithm.

[0088] The passive near-field coupling response unit does not require active transmission power. Its resonant response energy comes entirely from the external scanning electromagnetic field. The energy collected inside the body is only used to maintain the standby of the threshold detection module and trigger the switching action.

[0089] Example 5: Design and Verification of Online Adaptive Threshold Adjustment Mechanism

[0090] Based on Example 3, a further online adaptive threshold adjustment mechanism was designed and verified. The same batch of fibers was placed in three different simulated microenvironments:

[0091] Environment A: High MMP-9 (50 ng / mL) + Low pH (6.8) – Typical unstable plaque; Environment B: Moderate MMP-9 (10 ng / mL) + Normal pH (7.4) – Stable plaque; Environment C: Low MMP-9 (1 ng / mL) + Normal pH (7.4) – Healthy blood vessel.

[0092] Initially, all fibers use the same preset threshold parameters. After 48 hours of operation, fibers in environment A are expected to identify the "high-risk" mode and trigger a change in resonant state; fibers in environment B may trigger a small number of false positive responses; fibers in environment C are not expected to trigger a response.

[0093] After enabling the online adaptive threshold adjustment mechanism, the on-chip threshold detection module records the signal characteristics and trigger results of each detection, uses a local counter to statistically analyze the signal distribution, and automatically fine-tunes the discrimination threshold towards the individual baseline. It is expected that the false positive rate in environment B will be significantly reduced, while the detection rate in environment A will remain unchanged.

[0094] Example 6: Design Assessment of Biocompatibility and Long-Term Stability

[0095] The fibers obtained in Example 1 were immersed in simulated body fluid (SBF, pH 7.4, 37°C), and their designed electrochemical and mechanical properties were tested periodically.

[0096] (1) Electrochemical stability design target: During the 28-day immersion period, the open circuit voltage of the fiber is maintained at more than 80% of the initial value, and the short circuit current is maintained at more than 75%. The methacrylamide gelatin of the outer shell slowly swells in SBF (approximately 15% mass increase after 28 days) but does not disintegrate, effectively protecting the internal functional layer.

[0097] (2) Cell compatibility design goal: Co-culture of fibroblasts with vascular endothelial cells (HUVEC) for 72 hours, with an expected cell survival rate of >90%, which is not significantly different from the blank control group.

[0098] (3) Blood compatibility design target: After the fiber comes into contact with fresh human whole blood for 1 hour, the expected hemolysis rate is <5% (compliant with ISO 10993-4 standard), and the platelet adhesion rate is lower than 15% of the positive control (glass slide).

[0099] The above design evaluation results indicate that the fibers of this invention have good biocompatibility and expected long-term stability, meeting the basic requirements for intravascular implantation.

[0100] Beneficial effects

[0101] Compared with the prior art, the present invention has the following beneficial effects:

[0102] (1) Pioneering a new category of in vivo diagnostics with "autonomous power supply, edge discrimination, and molecular-level protection". This invention is the first to integrate energy harvesting, ultra-low power threshold discrimination based on organic electrochemical transistors and multi-target biochemical sensing heterogeneously into a single injectable nanofiber, realizing early warning and risk stratification of chronic vascular lesions.

[0103] (2) Innovative use of vascular pulsation pressure as an in vivo energy source. Through piezoelectric-triboelectric composite nanogenerators and innovative energy management strategies, this invention achieves system self-sufficiency at an average power input in the pW range, completely eliminating dependence on external power sources or toxic fuels.

[0104] (3) Achieving a true "implantable and forgettable" electronic sentinel. Through passive GHz resonant response and event-driven threshold discrimination, the system only changes the resonant state for external reading when pathological abnormalities are detected, and does not consume communication energy under normal circumstances, reducing energy consumption to the theoretical limit.

[0105] (4) Provides diagnostic information with molecular-level spatiotemporal precision. Through targeted ligand modification, the fibers are selectively anchored to the diseased vascular segment, measuring local core information directly related to the lesion, rather than diluted and delayed systemic indicators in the blood.

[0106] (5) Breakthroughs have been made in overcoming the limitations of silicon-based high-temperature processes on bioelectronic integration. Organic electrochemical transistors were fabricated using a fully low-temperature (<40℃) solution processing technology, which ensured the activity of biological functional molecules and made transistor integration on injectable fibers move from theoretical conception to engineering feasibility.

Claims

1. An injectable intelligent nanofiber intravascular pinpoint sensing system, characterized in that, include: One or more injectable, biocompatible composite nanofibers are included, wherein the composite nanofibers have a diameter of 100 nanometers to 50 micrometers and a length of 200 micrometers to 500 micrometers; the composite nanofibers integrate: an in vivo energy harvesting module, at least one on-chip sensing module, an on-chip threshold detection module, and a passive near-field coupling response unit; wherein the in vivo energy harvesting module is configured to convert the mechanical energy generated by vascular pulsation pressure into electrical energy and supply working power to the on-chip threshold detection module and the on-chip sensing module; the on-chip sensing module is configured to detect at least one biochemical parameter in the vascular microenvironment and transmit the detection signal to the on-chip threshold detection module; the on-chip threshold detection module is configured to receive the signal collected by the on-chip sensing module, perform a local threshold comparison, and output a trigger signal to change the response state of the passive near-field coupling response unit when the detection signal exceeds a predetermined threshold; The on-chip threshold detection module is an analog comparator operating in the subthreshold region based on an organic electrochemical transistor. The channel layer of the organic electrochemical transistor is a conductive polymer film, and the gate electrolyte is an ion gel or a solid electrolyte. The analog comparator is configured to perform threshold discrimination at an operating voltage below 100 mV. The passive near-field coupling response unit is configured to generate a characteristic resonant signal in response to an in vitro scanning electromagnetic field, and its resonant characteristics change detectably in response to the trigger signal. The passive near-field coupling response unit is an LC resonant circuit integrated on the composite nanofiber host. The resonant frequency of the LC resonant circuit is in the range of 0.5 GHz to 6 GHz, and the resonant frequency shifts in response to the trigger signal. The outer shell surface of the composite nanofiber host is modified with a targeting ligand for specific binding to target vascular endothelial cells or lesion tissue to achieve site-specific residence.

2. The system according to claim 1, characterized in that, The composite nanofiber body has a multi-layer coaxial structure, comprising, from the inside out: a core layer, which is a conductive polymer nanofiber serving as a signal transmission bus; an intermediate functional layer, which includes the in vivo energy harvesting module, the on-chip sensing module, and the on-chip threshold detection module; and an outer shell layer, which is a biocompatible hydrogel or a cell membrane-like coating modified with the targeting ligand for specific binding to target vascular endothelial cells or diseased tissues to achieve site-specific residence.

3. The system according to claim 2, characterized in that, The in vivo energy harvesting module is a micro piezoelectric-triboelectric composite nanogenerator based on a fiber structure. It is arranged along the fiber axis and designed to generate enough electrical energy to drive the on-chip threshold detection module and the on-chip sensing module under the small periodic deformation caused by vascular pulsation pressure.

4. The system according to claim 2, characterized in that, The on-chip threshold detection module includes: a single-transistor comparator or a dual-transistor differential pair comparator based on an organic electrochemical transistor, wherein the channel layer of the organic electrochemical transistor is composed of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate or poly(3-hexylthiophene), the source and drain electrodes are composed of inkjet-printed conductive polymers or metal nanowires, and the gate electrolyte is a composite ion gel of a fluorinated ionic liquid and a polymer matrix; a reference voltage generation unit coupled to the comparator, wherein the reference voltage is provided by a silver / silver chloride microelectrode integrated on a fiber or a voltage divider resistor network, and the reference voltage corresponds to a pre-stored pathological threshold; the comparator is configured to receive an analog signal from the on-chip sensing module and compare it with the reference voltage; the circuit outputs the trigger signal only when the analog signal exceeds the threshold corresponding to the reference voltage, thereby changing the response state of the passive near-field coupling response unit.

5. The system according to claim 1, characterized in that, The on-chip threshold detection module is an ultra-low power analog threshold discrimination unit based on organic electrochemical transistors, on which preset threshold parameters are embedded. The threshold discrimination unit is configured to: continuously monitor the raw signal of the sensing module locally, perform signal amplification and threshold discrimination, and distinguish between physiological fluctuations and pathological abnormal signals; only when a pathological signal exceeding the predetermined risk threshold is detected will the trigger signal be output to change the response state of the passive near-field coupling response unit, thereby transmitting an encoded response containing diagnostic information to the external receiver.

6. The system according to claim 5, characterized in that, The threshold parameter adopts an online adaptive adjustment mechanism, which can continuously optimize the local abnormality detection threshold based on the data distribution of the vascular microenvironment of a specific individual without relying on external raw data transmission, thereby achieving personalized monitoring.

7. The system according to claim 1, characterized in that, The passive near-field coupling response unit is an LC resonant circuit integrated on the composite nanofiber substrate, comprising: an inductive element composed of helical metal nanowires deposited on or inside the fiber surface, wherein the pitch of the helical metal nanowires is 200 nm to 2 μm and the linewidth is 50 nm to 500 nm; and a capacitive element composed of metal electrodes deposited in segments at both ends or on the surface of the fiber, wherein the capacitance of the capacitive element is 0.1 picofarad to 1 picofarad; the resonant frequency of the LC resonant circuit shifts in response to the trigger signal, and an external receiver reads the diagnostic information by detecting the shift in the resonant frequency; the passive near-field coupling response unit does not require active transmission power, and its energy comes from an external scanning electromagnetic field.

8. The system according to any one of claims 1 to 7, characterized in that, The injectability of the composite nanofibers is achieved through the following design: the fiber diameter is controlled between 100 nanometers and 50 micrometers, and the length is between 200 micrometers and 500 micrometers; it remains monodisperse in the injection fluid; it can pass smoothly through standard 25G to 32G injection needles; after injection into the bloodstream, it completes specific adhesion and settlement from free flow to the lesion area on the vascular wall within minutes to hours through surface ligand-receptor recognition, and the long axis of the settled fibers is aligned with the blood flow direction to minimize disturbance to the blood flow.

9. A method for preparing the system of claim 1, comprising the following key steps: Multilayer nanofibers are continuously drawn using coaxial electrospinning or microfluidic wet spinning techniques at ambient temperatures below 40 degrees Celsius. During or after drawing, sensing electrodes, piezoelectric layers, and organic electrochemical transistors are sequentially deposited in the middle section of the fiber using in-situ inkjet printing, photolithography, or electron beam direct writing techniques. The organic electrochemical transistors are formed by inkjet printing conductive polymer channel layers, source / drain electrodes, and ion-gel gate electrolytes. Helical metal nanowires are deposited on or inside the fiber to form inductive elements, and metal electrodes are segmentally deposited at both ends or on the surface of the fiber to form capacitive elements, constituting the passive near-field coupling response unit. Finally, a biocompatible shell and targeting ligands are modified using layer-by-layer self-assembly techniques. All steps involving biofunctional molecules in the entire preparation process are performed under sterile conditions below 40 degrees Celsius to ensure the activity of the biofunctional molecules.

10. A method for intravascular pinpoint diagnosis using the system of claim 1, comprising the steps of: A saline suspension containing the aforementioned intelligent nanofibers is injected into a blood vessel through a standard peripheral venous catheter or arterial sheath. The nanofibers circulate with the blood flow and autonomously locate themselves in predetermined vascular lesion areas through surface targeting modification. After the nanofibers are stationed, they are powered on using the pulsatile pressure energy of the blood vessel itself, activating the on-chip threshold detection module to begin continuous, non-invasive, in-situ monitoring of various protein, enzyme, and ion indicators. The on-chip threshold detection module only changes the resonant state of the passive near-field coupling response unit when it detects preset pathological thresholds such as plaque instability or increased risk of rupture. An external receiver scans and detects changes in the resonant state to obtain clinical graded alarms, thereby achieving "unmanned" vascular health monitoring without the need for continuous power supply or monitoring from external devices.

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