| Acupoint thread embedding therapy is an extension and development of acupuncture therapy.By implanting absorbable threads in human acupuncture points to obtain continuous stimulation to treat diseases,the emergence of one-time special thread embedding needles has entered the minimally invasive era.The minimally invasive implant thread,as the core material that determines the treatment effect,has undergone the development from sheep gut thread to biomedical degradable materials.At present,the amount and duration of stimulation are mainly controlled by adjusting the thickness and length of the embedded thread,but too thick or too long can cause problems such as fear and overflow injury in patients.Clinical experience has found that immersion of the implanted thread in the drug solution for a period of time then implant into the acupoint can enhance the efficacy of monotherapy.Therefore,in this paper,polyglycolide(PGA)braided thread with good biocompatibility and degradability is used as the matrix,and polycaprolactone(PCL)ligustrazine hydrochloride(TMPH)for injection is used as the drug controlled release system.The preparation of drug-loaded minimally invasive embedding threads in which pharmacological and physical stimuli coexisted in layers,and the preparation process was preliminary discussed.The influence of coating process on the performance of the embedding thread was first discussed.The results show that the addition of TMPH increases the surface roughness of the PCL film and drug particles are attached.When the concentration is above 5000 ?g/m L,the drug particles are dispersed uniformly,but the particle size is significantly increased when the concentration is too large.TMPH effects the crystallization process of PCL,transforming its crystal morphology from extended dendritic spherulites to distorted radial crystals.The drug-loaded coating makes the PGA braided threads more tightly entangled.As the PCL concentration or the number of coatings increases,the coating uniformity,integrity and coating amount increase,and the apparent braided structure of the thread tends to disappear.The size of the suture corresponding to the diameter of the embedding thread changes from 2-0 before coating to 2-0 to 2 after coating.In order to reduce the fear and pain of patients,choose the same specifications and the highest coating load parameters are more appropriate,that is,the PCL concentration is 5%,and the number of coatings is 5 times.The breaking strength of the embedded thread decreases and the elongation at break increases first and then decreases,and the softness deteriorates.The main contribution to the tensile properties is the braided thread matrix,and the main contribution to the softness is the drug-loaded coating.There are no new characteristic peaks outside the component melting curve and infrared spectrum of the embedding thread,indicating that no chemical reaction occurred between the components,but only physical blending and adhesion.The increase of the coating amount increases the drug loading of the embedding thread.Compared with the drug thread directly immersed in the drug solution,the drug loading of the embedding thread is increased by0.572 to 11.363 times,and the drug amount is different from each The relationship between the parameters changes from a simple linear correlation to a complex non-linear correlation.The drug release time of the drug-loaded embedding thread is longer,and the burst release phenomenon within the first 24 hours is improved to some extent.An embedding thread with a PCL concentration of 1%,a single coating layer number,or a drug concentration of 10,000?g/m L has a faster drug release rate than other samples.The release of TMPH in the simulated environment in vitro is divided into rapid release and stable release.The release law can be calculated using the first-order equation and Ritger-Peppas equation description.It release from the drug controlled release system is dominated by the drug's dissolution and diffusion mechanism,accompanied by the synergistic effect of the PCL backbone hydrolysis and erosion mechanism.Then the influence of weaving process on the performance of the embedding thread was discussed.The results show that the gear ratio has a significant effect on the structural parameters and mechanical properties of the braided thread(P<0.05).With the increase of the gear ratio,the morphological structure of the braided yarn gradually becomes tighter,and the inclination of the multifilament yarn increases;the diameter,the braided density,the braided angle,the elongation at break,and the compressive force all increase,and the fracture strength decreases.The covering of the coating eliminates the loosening phenomenon of the end of the braided thread,and makes the diameter of the thread body and the elongation at break.The rate and compressive force increase,the fracture strength decreases,and the influence of the weaving process on the diameter and mechanical properties of the thread body is weakened.The gear ratio has a significant effect on the coating amount and the embedding thread diameter(P<0.05).As the gear ratio increases,the coating amount decreases,and the diameter of the thread body fluctuates first,then decreases,and then increases,but all fall within the specified range of No.1 suture.The choice has little effect.The gear ratio has a significant effect on the mechanical properties of the embedding thread(P<0.05).As the gear ratio increases,the fracture strength of the embedding thread decreases and the elongation at break increases,and the compressive force floats in a trend of decreasing first and then increasing and then decreasing.The breaking strength and compressive force are maximum when the gear ratio is 82/26,and the breaking elongation reaches the maximum at 82/14.The drug loading capacity of the embedding thread decreases as the gear ratio increases.Drugs in threads with different gear ratios all have a sudden release within the first 24 hours,and the release rate is slowed and stabilized afterwards.The cumulative drug release rate of the embedding thread with a gear ratio of 82/34 is higher,while the drug release rate difference between the other embedding threads is smaller.Finally,the performance changed of the embedding thread during degradation in vitro were discussed,and its biocompatibility was evaluated by in vitro cytotoxicity experiments.The results show that as the degradation time prolongs,the monofilament in the PGA braided thread breaks through the ester bond due to hydrolysis,and grooves and cracks are gradually produced until it breaks.The wrapping of the drug-loaded coating keeps the braided thread skeleton more complete.TMPH in the coating is completely released within 1w,and its melting peak and infrared absorption peak disappeares.The resulting pores and stress concentration effect cause the coating to undergo large-area damage when it is degraded at 3w,and the protective effect of the coating was greatly reduced.Compared with the uncoated braided thread,the mechanical properties of the implanted thread decline more slowly,but the strength of more than 46.65% and the elongation of more than 61.94% are still lost after the first week of degradation.The increase of the gear ratio makes the braided structure tighter,the coating uniformity and integrity improved,and the thread body retains a more complete micro-aggregated structure and macro-morphological structure due to the slower hydrolysis,showing better mechanical properties.The embedding thread structure of the 82/26 gear ratio is more reasonable,which maintains a relatively high hardness.The positive effect brought by the increase of coating and gear ratio is more obvious in the initial stage of degradation,which weakens with the prolongation and intensification of hydrolysis,resulting in the difference in the mechanical properties of each embedding thread narrow and eventually lost.Based on the qualitative evaluation of cell morphology and the quantitative evaluation of cell proliferation rate,the cytotoxicity of PGA braided thread,PCL coated embedding thread and drug-loaded minimally invasive embedding thread is rated as Grade 1,Grade 0 ~ 1 and Grade 0,respectively.Indicating that all three have good biocompatibility.In summary,changes in the coating process and weaving process will have different effects on the physicochemical properties and drug release properties of the drug-loaded minimally invasive embedding thread.This makes it possible to obtain a preset performance-loaded acupoint embedding thread by comprehensively controlling the coating and weaving process,and provides an experimental basis for its subsequent research and clinical application. |
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