Intelligent innovation and application performance control of hydrogel dressing in wound monitoring and drug controlled release

Abstract: hydrogel dressing, because of its good liquid absorption, good biocompatibility, water vapor permeability and good extensibility and stickiness, can provide a good healing environment for the wound, and at the same time, bring comfortable experience to the patient With the development of technology, "wound monitoring" and "drug controlled release" have been gradually realized through the functional renovation of hydrogel dressing, and the hydrogel dressing has been pushed into the wave of intellectualization It should be noted that the key properties such as viscosity, comfort and moisture permeability still need to be controlled Key words: hydrogel dressing, wound monitoring, drug release, sticky, comfort, daily work and life, injuries can hardly be avoided As a wound covering, medical dressing plays an important role in absorbing exudate, controlling wound infection and accelerating wound healing In recent years, with the rapid development of modern medicine and material science, many new medical dressings have been applied in clinic, such as hydrogel dressing After the function of dressing and the damage of skin tissue, only after the complex function of inflammatory cells such as neutrophils and repair cells such as fibroblasts and epidermal cells, can the wound heal completely In this process, in order to prevent secondary infection, wound surface is usually covered with dressing to protect The ideal dressing can prevent the formation of fine skin, not adhere to the new granulation tissue, create a low oxygen environment, reduce scar formation, and accelerate the healing speed Therefore, it is necessary for the dressing to have proper water vapor permeability, oxygen permeability, good liquid absorption, good mechanical properties and biocompatibility At present, the clinical dressing is mainly made of absorbent cotton gauze, non-woven dressing, membrane dressing and hydrogel dressing Gauze and non-woven dressing have good air permeability and moisture permeability, but the amount of liquid absorption is not large enough The appearance of the film dressing is transparent, and it is easy to observe the wound healing If we choose the film material with different permeability, such as polyurethane, nylon 6, polyethylene, etc., we can create a suitable humidity and oxygen environment for wound healing But it is also the problem of liquid absorption capacity that limits its application Hydrogel dressings are a kind of gelatinous substance with three-dimensional net structure and insoluble in water, formed by water-soluble polymer materials or monomers It has smooth surface, good biocompatibility, and can repeatedly hydrate when contacting with the wound, absorbing the tissue fluid exuded from the wound At the same time, hydrogel dressing has a certain degree of viscosity and ductility, and can be closely linked to the wound, reduce the incidence of infection, but it does not change with the wound adhesion In terms of moisture permeability and oxygen permeability, the results of related studies indicate that the performance of hydrogels is not stable and needs further research In general, hydrogel dressing is a good choice for "ideal dressing" at present Intelligent renovation of hydrogel dressing has injected fresh blood into the development of medical dressings in recent years Smart dressings have become an important fulcrum for the reform and upgrading of dressing industry Because of the many advantages of hydrogel dressing, its intelligent innovation has attracted the attention of many scholars and technicians For example, engineers from Massachusetts Institute of Technology have designed an intelligent hydrogel dressing that can monitor the wound temperature and release the drug to the wound When the drug is running out, the dressing will shine This combination of temperature sensors, LED lights, and mini drug delivery repository, channel and traditional hydrogel dressing reflects two directions of intelligent renovation of current gel dressing: wound monitoring and drug controlled release 1 Wound healing monitoring is a complex biological reaction process Under suitable conditions, such as environmental humidity, pH value, temperature, etc., it will accelerate the healing speed, on the contrary, it will slow down the healing, even lead to infection and show specific characteristics According to the theory of "wet wound healing", wet ring is conducive to the enhancement of immune cells, especially leukocytes, and the acceleration of epidermal cell migration The healing speed of wound in a suitable wet environment is twice as fast as that in a dry environment In addition, the pH value of wound is also an influential factor in the healing process When the environmental pH value of the wound is 5, the inhibition effect on bacteria is the best, and when the pH value is increased, it is gradually conducive to the growth of bacteria Therefore, keeping the acid environment of wound surface can reduce the probability of bacterial infection When the wound is infected, there will be subtle changes in the wound, such as temperature rise, special smell and so on It has been proved that keeping the temperature of wound close to or constant to the normal temperature of human body at 37 ℃ and the cell mitosis rate increased by 108%, is also conducive to the rapid healing of wound For medical staff, regular inspection of the wound surface is conducive to their accurate understanding of the wound microenvironment and whether the wound is infected, which is particularly important for the development of follow-up treatment strategies However, the contradiction is that frequent dressing replacement will cause the fluctuation of temperature and humidity of wound microenvironment, disturb the normal healing, and increase the risk of infection to a greater extent Based on this, one direction of intelligent renovation of hydrogel dressing is "wound monitoring" By embedding different functional wireless sensors, such as temperature sensors, humidity sensors, pH sensors, odor sensors, etc., into the hydrogel dressing, a portable intelligent device can be used to monitor the wound information of patients in real time without needing to replace the material Whether the environment is suitable and whether infection occurs With the support of modern "cloud storage" technology, the data of wound healing is more convenient to achieve long-term preservation, which is conducive to the development of deep wound healing research 2 The release of traditional controlled release drugs mainly depends on the free diffusion of drug molecules, which is closely related to drug concentration If it can make the release of drugs slow and controllable, it can prolong the half-life of drugs, realize the release of drugs in time, quantity and location, reduce the times of administration, and reduce the frequency of dressing replacement Therefore, "drug controlled release" has become another direction of intelligent research of hydrogel dressing Unlike the "wound monitoring hydrogel dressing", "drug controlled release hydrogel dressing" is not based on the external structure, but is based on the extended application of hydrogel's own properties These hydrogel dressings are responsive to environmental stimuli such as temperature, light, electric field, magnetic field, pH and stress, such as gelation, shrinkage, swelling and volume changes Moreover, with the reversibility of stimulation, the change of hydrogel character is reversible On the basis of this principle, on the one hand, the release of drugs can be controlled by the change of the sol-gel phase of hydrogel For example, researchers have incorporated NIR responsive nanoparticles into photoglysis of o-nitrobenzyl hydrogels When the hydrogel is exposed to near infrared radiation, the nanoparticles convert the absorbed near-infrared light to ultraviolet light, resulting in a "sol gel" change in the hydrogel, which releases drug components On the other hand, the controlled release of drugs can also be achieved by volume contraction of hydrogels Taking poly N- isopropylacrylamide (PNIPAM) thermosensitive hydrogel as an example, Zhang Yanning, Southwest Jiao Tong University, dispersed the PDA NPs particles of mussel material into N- isopropylacrylamide (NIPAM) monomer and formed PDA/PNIPAM hydrogels through free radical polymerization Due to the high efficiency photothermal conversion of PDA particles and the thermo sensitive properties of poly N- isopropylacrylamide (PNIPAM) under the near infrared radiation, the structure of PDA/PNIPAM hydrogel is collapsed under the NIR stimulus, the volume shrinks, and the drug components are pulsed The performance of intelligent hydrogel dressings is controlled in terms of performance requirements Stickiness, comfort and moisture permeability are still the key points for the performance control of intelligent hydrogel dressings, in order to ensure the stability of the dressing and the suitable environment for the wound Because the wound monitoring and drug controlled release intelligent hydrogel dressing is improved inside and outside the gel dressing, the change of performance is more difficult to grasp and become one of the difficulties in the application of intelligent hydrogel dressing Therefore, when studying the intelligent application of hydrogel dressing, we should not neglect its key performance monitoring and research At present, for the performance control of hydrogel dressing, we can refer to China pharmaceutical industry standard YY/T 1293.4-2016 "contact wound dressing The fourth part: hydrocolloid dressings, which specifies the appearance, size, liquid absorption, water resistance, viscosity, comfort, acidity, alkalinity, heavy metal, bacteria resistance, asepsis, biocompatibility and other performance requirements and test methods of hydrogel dressing, which was implemented in June 1, 2017 Stickiness reflects the ability of hydrogel dressing to be tightly adhered to skin In the standard, it is characterized mainly by "Stickiness" and "peel strength" The adhesion test is to use the pressure roller to contact and bond the bonding surface of the sample with the surface of the stainless steel sheet, hang a weight at the suspension end of the sample according to the standard of 0.8N (80g) per cm width, and place it in a hot air oven at 36 ℃ ~ 38 ℃ for 30min, during which the top of the sample attached to the stainless steel sheet shall not slide more than 2.5mm The peel strength test is also to stick the sample to the center of the clean surface of the stainless steel plate by the pressure roller, and to test the required force value of the 180 ° peel sample by the intelligent electronic tensile testing machine The peel speed is 270mm / min ~ 330mm / min According to the standard requirements, the average force required for every 1cm width of the sample shall not be less than 1n The comfort of hydrogel dressing test shows the ability of hydrogel dressing to adapt to the shape and movement of human body When the dressing is used in joints and other moving parts, it is very important to have sufficient freedom of movement When the dressing is easy to stretch and can basically return to the original position, it can prevent the subcutaneous shear injury, and the patient will feel comfortable Therefore, "extensibility" and "permanent (separator) deformation" are two indicators of comfort The specific test method is: cut a (25 ± 0.5) mm wide strip sample and relax for 300s Make two parallel marks with a spacing of (100 ± 10) mm on the sample so that the distance between the two marks is equal to the distance between the two ends The part from outside to both ends of the sample marking line is clamped in the upper and lower collets of the intelligent electronic tensile testing machine, and the sample is extended by 20% at a tensile speed of (300 ± 10) mm / min The instrument automatically records the minimum load at this time Hold at this tensile position for (60 ± 1) s, remove the sample and relax for (300 ± 15) s Measure the distance between the two marks on the sample again Calculate the result according to the following formula Extensibility (n / cm) = minimum load / 2.5 permanent (separator) long deformation (%) = (distance between two gauges after stretching - distance between two gauges before stretching) / distance between two gauges before stretching × 100% Hydrogel dressing extensibility and permanent (separator) long deformation test example moisture permeability, at present, there is no performance related to hydrogel dressing and test standards, generally refer to China pharmaceutical industry standard YY/T 0471.2-2004 "contact wound dressing test method second parts: breathable membrane dressing vapor transmission rate" test, the principle is through weighing the square.