Poly(lactide-co-glycolide) encapsulated hydroxyapatite microspheres for sustained release of doxycycline

The purpose of this study was to prepare a poly(lactide-co-glycolide) (PLGA) encapsulated hydroxyapatite microspheres (HAP-MSs) as injectable depot for sustained delivery of Doxycycline (Doxy). Doxy loaded HAP-MSs (Doxy-HAP-MSs) were encapsulated with PLGA by solid-in-oil-in-water (S/O/W) emulsion-solvent evaporation technique, the effects of the PLGA used (various intrinsic viscosity and LA/GA ratio) and ratio of PLGA/HAP-MSs on the formation of Doxy-HAP-MSs and in vitro release of Doxy were studied. The results showed that sustained drug release without obvious burst was obtained by using PLGA encapsulated HAP-MSs as the carrier, also the drug release rate could be tailored by changing the ratio of PLGA/HAP-MSs, or PLGA of various intrinsic viscosities or LA/GA ratio. Lower ratio of PLGA/HAP-MSs corresponded faster Doxy release, e.g. for the microspheres of PLGA/HAP-MSs ratio of 8 and 0.25, the in vitro Doxy release percents at the end of 7days were about 23% and 76%, respectively. Higher hydrophilicity (higher ratio of GA to LA) and lower molecular weight of PLGA corresponded to higher Doxy release rates. For in vivo release study, PLGA encapsulated HAP-MSs were subcutaneously injected to the back of mice, and the results showed good correlation between the in vivo and in vitro drug release. Meanwhile, the plasma Doxy levels after subcutaneous administration of PLGA encapsulated Doxy-HAP-MSs were relatively lower and steady compared to that of the un-encapsulated microspheres. In conclusion, PLGA encapsulated HAP-MSs may be a potential vehicle for the sustained delivery of Doxy.     

RP-HPLC法测定泰妙菌素与多西环素的含量

概述了RP—HPLC法测定复方泰妙菌素可溶性粉中泰妙菌素和多西环素含量的方法。采用Shim—pack CLE—ODS柱（150mm×6mm,5μm）,流动相为80％乙腈-0．7％磷酸氢二铵（体积比为0．3：0．7）,并用氨试液调节pH至8．0±0．1。流速为1．0mL·min^-1,泰妙菌素检测波长为208nm,多西环素检测波长为272nm,柱温为40℃。在此色谱条件下两者能完全分离,泰妙菌素和多西环素在10μg·mL^-1～100μg·mL^-1的范围内浓度与峰面积呈良好的线性关系,回归方程和相关系数分别为：A=47505．7p＋1003．32,R=0．9999;A=47357p＋5587．3,R=0．9999。泰妙菌素和多西环素的回收率分别为99．51％～99．84％、99．75％～100．2％;RSD分别为0．30％-0．75％、0．45％-0．80％。实验表明,该方法简便、准确,可用于复方泰妙菌素可溶性粉的含量测定。     

碱性降解-Al~(3+)络合物形成荧光法测定强力霉素

本文提出了荧光法测定强力霉素(DC)的新方法。强力霉素碱性降解后与铝离子形成强荧光的络合物,并据此进行荧光测定,其荧光强度在4.0×10~(-8)～7.0×10~(-6)mol/L 范围内与强力霉素浓度成正比,共存的其它四环素类抗菌素不干扰强力霉素的测定,测定的检测限为3.0×10~(-8)mol/L。此法用于血清和尿液中强力霉素的测定,回收率分别为93～97%和91%～99%。     

Development of a highly sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay for determination of doxycycline in chicken muscle,liver and egg

A modified indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method was developed using a highly sensitive and specific monoclonal antibody (McAb) to determine doxycycline (DC) residues in chicken tissues and egg. The McAb against DC was produced by hybridoma technique and a modified ic-ELISA was characterised in terms of sensitivity, specificity, precision and accuracy. At optimal experimental conditions, the standard curve was constructed at concentrations ranged from 0.01 to 100 ng/ml. The IC₅₀ value was 1.32 ± 0.18 ng/ml. The limit of detection was 0.14 ± 0.02 ng/g. The recoveries of DC from spiked chicken liver, muscle, and egg at levels of 50–600 ng/g were 84.6–85.5%, 88.2–89.1%, and 84.4–89.3%, respectively. The coefficient variations (CVs) were 5.1–9.3%, 3.7–11.3%, and 4.7–9.8%, respectively. Linear regression analysis showed good correlation, with r² values 0.9909 for chicken liver and 0.9916 for chicken muscle.     

The effect of chemical composition and morphology on the drug delivery properties of hydroxyapatite-based biomaterials

In the case of orthopedic and dental interventions, local antibiotic therapy reduces significantly the risk associated with the intervention. The aim of this study was the preparation and characterization of pure hydroxyapatite (HA), Si- and Mg-doped HA, which ensures the sustained release of doxycycline, and the investigation of the parameters, which were crucial for the drug release. The carriers were synthesized using the precipitation method. In order to achieve different morphologies, traditional drying and spray drying methods were used: Si-doped HA was prepared using two different sources of Si, Na₂SiO₃ and Ludox AS-40, while (Mg(NO₃)₂)*6H₂O was used for substitution with Mg. The carriers were characterized by XRD, SEM, EDX and TG/DTA methods, and the ion incorporation was also confirmed by lattice parameters calculations. Doxy was bound on the carriers by physical adsorption, the adsorption capacity increased proportionally by increasing the concentration of the initial Doxy solutions (10, 15, 20, 25 g/L). The investigated systems showed different releases with the change of the dissolution medium (in the case of HA microspheres, the release in PBS was twice as high as in SBF), chemical composition and morphology of the carriers. The retard effect of the carriers was improved by the spherical morphology, and the reduced release by ion substitution in both SBF and PBS increased as follows: HA < HASi1<HAMg < HASi2. The release mechanism of Doxy was discussed through five different release kinetics models.     

Construction of a Z-scheme Cu2O/SrBi4Ti4O15 p–n heterojunction for enhanced visible light photocatalytic performance for doxycycline degradation

p–n heterojunction composites with high-charge-transfer efficiency have attracted considerable attention owing to their unique structure and interface interactions. Herein, a novel Z-scheme Cu₂O/SrBi₄Ti₄O₁₅ p–n heterojunction was successfully constructed using the microwave hydrothermal method for DOC removal under visible light irradiation. The structure, composition, and photoelectric chemical properties of Cu₂O/SrBi₄Ti₄O₁₅ nanocomposites were studied. The composites exhibited high photocatalytic activity for DOC, and 92.2% of DOC was decomposed within 60 min, which is 9.2 and 5.2 times higher than those of original Cu₂O and SrBi₄Ti₄O₁₅, respectively. The extraordinary degradation performance can be attributed to the formation of Z-scheme heterostructure. On the one hand, a unique interface structure can significantly enhance the number of active sites on the catalyst surface. On the other hand, Z-scheme heterostructure can accelerate generation and migration of the photoinduced carriers. Furthermore, the effects of operational parameters such as catalyst dosage, initial concentration, inorganic salts, and water sources, were investigated. Finally, a photodegradation mechanism of Z-scheme Cu₂O/SrBi₄Ti₄O₁₅ p–n heterojunction for DOC was proposed.