阅读说明：本技术 一种pH响应性恩诺沙星纳米颗粒及其制备方法和应用 (PH-responsive enrofloxacin nanoparticles and preparation method and application thereof ) 是由 鲍光明 杨俊岚 袁厚群 王立琦 王小莺 何嘉欣 宋德平 邓科 于 2021-08-05 设计创作，主要内容包括：本发明公开了一种pH响应性恩诺沙星纳米颗粒及其制备方法和应用,该pH响应性恩诺沙星纳米颗粒由壳聚糖与肉桂醛接枝形成载体,封装恩诺沙星获得。本发明制得的pH响应性恩诺沙星纳米颗粒的平均药物包封率为76.6％,负载量为3.3％,具有单分散性、酸敏感性和酸触发药物释放特性,并且由于其优异的酸响应释放曲线和体外释放,使之可作为细菌感染DDS和苦味恩诺沙星的味道掩蔽剂。本发明使用的肉桂醛和壳聚糖是具有抗菌活性的天然产物,廉价且易于获得。(The invention discloses a pH-responsive enrofloxacin nanoparticle, a preparation method and application thereof. The pH-responsive enrofloxacin nano particles prepared by the invention have the average drug encapsulation rate of 76.6 percent and the loading amount of 3.3 percent, have monodispersity, acid sensitivity and acid-triggered drug release characteristics, and can be used as a taste masking agent for bacterial infection DDS and bitter enrofloxacin due to excellent acid-responsive release curve and in-vitro release. The cinnamaldehyde and chitosan used in the present invention are natural products having antibacterial activity, are inexpensive and easily available.)

1. The pH-responsive enrofloxacin nanoparticles are characterized in that a carrier is formed by grafting chitosan and cinnamyl aldehyde, and enrofloxacin is encapsulated to obtain the pH-responsive enrofloxacin nanoparticles.

2. The pH-responsive enrofloxacin nanoparticles of claim 1, wherein said pH-responsive enrofloxacin nanoparticles are monodisperse and acid sensitive.

3. A preparation method of pH-responsive enrofloxacin nanoparticles is characterized by comprising the following steps:

dropwise adding cinnamaldehyde into a 1% acetic acid aqueous solution containing chitosan, and stirring for 1h to obtain a first mixture; dropwise adding an anhydrous ethanol solution containing enrofloxacin into a mixture of SPAN80 and liquid paraffin to obtain a second mixture; slowly adding the first mixture into the second mixture, adjusting pH to 6.3, stirring at 40 deg.C for 3-4 hr, and centrifuging; repeatedly washing the residue with petroleum ether and double distilled water to obtain pH-responsive enrofloxacin nanoparticles;

wherein, the weight ratio of cinnamaldehyde: 1% acetic acid solution containing chitosan: anhydrous ethanol solution containing enrofloxacin: SPAN 80: liquid paraffin 1 mL: 20mL of: 2mL of: 2 g: 80 mL; 0.2g of chitosan is contained in each 20mL of the 1% acetic acid solution containing the chitosan, and 29.9-30.3mg of enrofloxacin is contained in each 2mL of the anhydrous ethanol solution containing the enrofloxacin.

4. The method for preparing pH-responsive enrofloxacin nanoparticles according to claim 3, wherein pH is adjusted to 6.3 with 10% NaOH.

5. The method for preparing pH-responsive enrofloxacin nanoparticles according to claim 3, wherein the centrifugation conditions are: centrifuge at 12000rpm for 30 min.

6. The method for preparing pH-responsive enrofloxacin nanoparticles according to claim 3, wherein the residue is repeatedly washed 5 times with petroleum ether and double distilled water.

7. The method for preparing pH-responsive enrofloxacin nanoparticles according to claim 3, wherein the pH-responsive enrofloxacin nanoparticles are freeze-dried and stored in a place dry from the sun.

8. Use of the pH-responsive enrofloxacin nanoparticles of claim 1 or 2 as a taste masking agent for bitter enrofloxacin.

Technical Field

The invention belongs to the technical field of antibacterial drugs, and particularly relates to pH-responsive enrofloxacin nanoparticles as well as a preparation method and application thereof.

Background

Enrofloxacin belongs to synthetic antibacterial agents of fluoroquinolone class, is a widely used broad-spectrum antibiotic, and has good prevention and treatment effects on common respiratory tract and intestinal tract bacterial diseases and mycoplasma of livestock and poultry. The antibacterial mechanism is to inhibit bacterial DNA gyrase and topoisomerase IV and stop the replication, transcription and repair of bacterial DNA and chromosome division of bacterial cell wall, thereby blocking the replication of bacterial DNA and achieving the purpose of bacteriostasis. Enrofloxacin has the advantages of rapid antibacterial and bactericidal action, excellent oral absorption and tissue distribution, small toxic and side effects, stable blood concentration, no cross drug resistance with other antibiotics and drug resistance to diseases caused by medicinal bacterial infection. However, enrofloxacin has strong irritation to the gastrointestinal tract, easily causes stress to animals during administration, and requires repeated administration many times during the treatment. The common enrofloxacin slow release preparation can reduce the irritation and the administration times of enrofloxacin and realize continuous administration, but the long-term administration with low dosage can increase the risks of side effects of medicaments and drug-resistant bacteria. Therefore, the development of an effective bacteria-reactive drug delivery system (BRDDS) is a necessary condition for achieving drug inhibition of bacterial infection.

During the bacterial infection process, bacteria secrete a plurality of active factors, acidic substances are generated through low-oxygen fermentation to reduce the surrounding pH value, and finally a unique bacterial infection microenvironment is formed. Furthermore, the site of bacterial infection has an Enhanced Permeability and Retention (EPR) effect similar to that of tumor tissue, favoring the aggregation of more nanoparticles to the site of bacterial infection through passive targeted transport. When animals are infected with acid-producing bacteria such as staphylococcus aureus, the bacteria can grow and propagate on local focuses of the body in a large quantity, and the focuses are in an acidic state. It is therefore highly desirable to develop a simple and efficient strategy for preparing a pH responsive enrofloxacin delivery system and an inexpensive livestock and poultry carrier material.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a pH-responsive enrofloxacin nano particle and a preparation method and application thereof, and the following technical scheme is specifically adopted:

a pH-responsive enrofloxacin nanoparticle is obtained by grafting chitosan and cinnamaldehyde to form a carrier and encapsulating enrofloxacin.

Preferably, the pH-responsive enrofloxacin nanoparticles have monodispersity and acid sensitivity.

Preferably, the pH-responsive enrofloxacin nanoparticles act as a taste masking agent for bitter enrofloxacin.

The invention also provides a preparation method of the pH-responsive enrofloxacin nano particles, which comprises the following steps:

dropwise adding cinnamaldehyde into a 1% acetic acid aqueous solution containing chitosan, and stirring for 1h to obtain a first mixture; dropwise adding an anhydrous ethanol solution containing enrofloxacin into a mixture of SPAN80 and liquid paraffin to obtain a second mixture; slowly adding the first mixture into the second mixture, adjusting pH to 6.3, stirring at 40 deg.C for 3-4 hr, and centrifuging; repeatedly washing the residue with petroleum ether and double distilled water to obtain pH-responsive enrofloxacin nanoparticles (ENR-NPs);

wherein, the weight ratio of cinnamaldehyde: 1% acetic acid solution containing chitosan: anhydrous ethanol solution containing enrofloxacin: SPAN 80: liquid paraffin 1 mL: 20mL of: 2mL of: 2 g: 80 mL; 0.2g of chitosan is contained in each 20mL of the 1% acetic acid solution containing the chitosan, and 29.9-30.3mg of enrofloxacin is contained in each 2mL of the anhydrous ethanol solution containing the enrofloxacin.

According to the invention, chitosan and cinnamaldehyde are grafted to form a carrier, and then the pH is specifically adjusted to be 6.3 and enrofloxacin is encapsulated, so that enrofloxacin nano particles with pH response characteristics are prepared. Meanwhile, the functionalized chitosan with cinnamaldehyde generates an amphiphilic copolymer and serves as a carrier, and an oil-in-water (O/W) nano emulsion system is formed in the presence of enrofloxacin. When bacterial infection occurs, the local environment is acidified due to bacterial reproduction, so that enrofloxacin nano particles with pH response characteristics are induced to respond, and enrofloxacin is released.

Preferably, the pH is adjusted to 6.3 with 10% NaOH.

Preferably, the centrifugation conditions are: centrifuge at 12000rpm for 30 min.

Preferably, the residue is washed repeatedly 5 times with petroleum ether and double distilled water.

Preferably, the pH-responsive enrofloxacin nanoparticles (ENR-NPs) are freeze-dried and stored in a dry place protected from light

The invention has the beneficial effects that: the pH-responsive enrofloxacin nanoparticles (ENR-NPs) prepared by the method have the average drug encapsulation rate of 76.6 percent and the loading amount of 3.3 percent, have monodispersity, acid sensitivity and acid-triggered drug release characteristics, and can be used as a taste masking agent for bacterial infection DDS and bitter enrofloxacin due to the excellent acid-responsive release curve and in-vitro release. The cinnamaldehyde and chitosan used in the present invention are natural products having antibacterial activity, are inexpensive and easily available.

Drawings

FIG. 1 is a diagram showing the preparation, pH triggered release mechanism and bacteriostatic effect of ENR-NPs of the present invention;

FIG. 2 is an X-ray diffraction pattern of chitosan, CS-CA-NPs and ENR-NPs of the present invention;

FIG. 3 is an infrared spectrum of chitosan, cinnamaldehyde, CS-CA-NPs and ENR-NPs of the present invention;

FIG. 4 is a transmission electron microscope image of the ENR-NPs of the present invention;

FIG. 5 is a size distribution of the DLS analysis of the present invention;

FIG. 6 is a zeta potential of ENR-NPs according to the present invention;

FIG. 7 is a transmission electron microscope image of ENR-NPs after 12 hours of release under pH 5.0 conditions of the present invention;

FIG. 8 is a pH-dependent release profile of ENR-NPs of the present invention in PBS solution;

FIG. 9 shows that enrofloxacin of the present invention has activity against Staphylococcus aureus at pH 7.4 or pH 5.0 and ENR-NPs at pH 7.4 or pH 5.0.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, aspects and effects of the present invention.

Materials and reagents of the invention:

chitosan (degree of deacetylation is more than or equal to 95%, viscosity is 100-;

glacial acetic acid (the purity is more than or equal to 99.5%), absolute methanol (the purity is more than or equal to 99.5%), sodium hydroxide (the purity is more than or equal to 99%), sodium dihydrogen phosphate dihydrate (the purity is more than or equal to 99%), disodium hydrogen phosphate dodecahydrate (the purity is more than or equal to 99%), petroleum ether (60-90) and liquid paraffin, which are purchased from Xilongsconsin technologies, Inc.;

cinnamaldehyde (purity is more than or equal to 95%) is purchased from Tianjin Dagmang chemical reagent factory;

SPAN80 was purchased from national pharmaceutical group chemical industries;

enrofloxacin (purity more than or equal to 98%) was purchased from Zhejiang national Pont pharmaceutical Co., Ltd;

the TSB culture medium is purchased from Hangzhou base biotechnology limited;

staphylococcus aureus (ATCC25923) was purchased from ruwei science;

agar powder was purchased from Shanghai Merlin Biochemical Co., Ltd.

Example 1

Preparation of pH-responsive enrofloxacin nanoparticles (ENR-NPs)

(1) Adding 1mL of cinnamaldehyde into 20mL of 1% (v/v) acetic acid aqueous solution containing 0.2g of chitosan dropwise, and stirring for 1h to obtain a mixture containing cinnamaldehyde and chitosan;

(2) dropwise adding 2mL of an absolute ethanol solution containing 30.1mg of enrofloxacin into a mixture of 2g of SPAN80 and 80mL of liquid paraffin to obtain a mixture containing enrofloxacin;

(3) slowly adding a mixture containing cinnamaldehyde and chitosan into a mixture containing enrofloxacin, adjusting the pH of the solution to 6.3 by using 10% NaOH, stirring for 3.5h at 40 ℃, and then centrifuging for 30min at 12000rpm to obtain a residue;

(4) repeatedly washing the residue with petroleum ether and double distilled water for 5 times to obtain pH-responsive enrofloxacin nanoparticles (ENR-NPs);

(5) the ENR-NPs precipitate was freeze-dried and stored in a dry place protected from light.

Example 2

Preparation of pH-responsive enrofloxacin nanoparticles (ENR-NPs)

(1) Adding 1mL of cinnamaldehyde into 20mL of 1% (v/v) acetic acid aqueous solution containing 0.2g of chitosan dropwise, and stirring for 1h to obtain a mixture containing cinnamaldehyde and chitosan;

(2) dropwise adding 2mL of an absolute ethanol solution containing 29.9mg of enrofloxacin into a mixture of 2g of SPAN80 and 80mL of liquid paraffin to obtain a mixture containing enrofloxacin;

(3) slowly adding a mixture containing cinnamaldehyde and chitosan into a mixture containing enrofloxacin, adjusting the pH of the solution to 6.3 by using 10% NaOH, stirring for 3.5h at 40 ℃, and then centrifuging for 30min at 12000rpm to obtain a residue;

(4) repeatedly washing the residue with petroleum ether and double distilled water for 5 times to obtain pH-responsive enrofloxacin nanoparticles (ENR-NPs);

(5) the ENR-NPs precipitate was freeze-dried and stored in a dry place protected from light.

Example 3

Preparation of pH-responsive enrofloxacin nanoparticles (ENR-NPs)

(1) Adding 1mL of cinnamaldehyde into 20mL of 1% (v/v) acetic acid aqueous solution containing 0.2g of chitosan dropwise, and stirring for 1h to obtain a mixture containing cinnamaldehyde and chitosan;

(2) dropwise adding 2mL of an absolute ethanol solution containing 30.3mg of enrofloxacin into a mixture of 2g of SPAN80 and 80mL of liquid paraffin to obtain a mixture containing enrofloxacin;

(3) slowly adding a mixture containing cinnamaldehyde and chitosan into a mixture containing enrofloxacin, adjusting the pH of the solution to 6.3 by using 10% NaOH, stirring for 3.5h at 40 ℃, and then centrifuging for 30min at 12000rpm to obtain a residue;

(4) repeatedly washing the residue with petroleum ether and double distilled water for 5 times to obtain pH-responsive enrofloxacin nanoparticles (ENR-NPs);

(5) the ENR-NPs precipitate was freeze-dried and stored in a dry place protected from light.

Example 4

Preparation of Chitosan-Cinnamaldehyde nanoparticles (CS-CA-NPs)

(1) Adding 1mL of Cinnamaldehyde (CA) dropwise into 20mL of 1% (v/v) acetic acid aqueous solution containing 0.2g of Chitosan (CS), and stirring for 1h to obtain a mixture containing cinnamaldehyde and chitosan;

(2) dropwise adding 2mL of absolute ethyl alcohol solution into a mixture of 2g of SPAN80 and 80mL of liquid paraffin to obtain a mixture;

(3) slowly adding a mixture containing cinnamaldehyde and chitosan into the mixture prepared in the step (2), adjusting the pH of the solution to 6.3 by using 10% NaOH, stirring for 3.5h at 40 ℃, and then centrifuging for 30min at 12000rpm to obtain a residue;

(4) the residue was repeatedly washed with petroleum ether and double distilled water for 5 times to obtain chitosan-cinnamaldehyde nanoparticles (CS-CA-NPs).

Example 5

XRD analysis of CS, CS-CA-NPs and ENR-NPs

The crystal structures of chitosan, CS-CA-NPs and ENR-NPs by XRD are shown in FIG. 2. Two characteristic peaks at 2 θ ═ 12.05 ° and 20.39 ° in the CS diffractogram indicate hydrogen bonding of chitosan chains and highly deacetylated type II. When chitosan is coupled with cinnamaldehyde, the diffraction peak disappears at 2 θ ═ 12.05, and the peak intensity decreases at 2 θ ═ 20.39, indicating that cross-linking between the amino groups of chitosan and cinnamaldehyde groups destroys the crystalline structure of chitosan. Diffraction peaks of enrofloxacin on ENR-NPs indicate that enrofloxacin is dispersed in the ENR-NPs in a solid form.

Example 6

FT-IR spectral analysis of chitosan, cinnamaldehyde, CS-CA-NPs and ENR-NPs

The chitosan, cinnamaldehyde, CS-CA-NPs, and ENR-NPs were characterized using Fourier transform infrared (FT-IR) spectroscopy, as shown in FIG. 3. CS-CA-NPs and ENR-NPs are 1635cm^-1The peak indicates a characteristic peak of a C ═ N double bond in imine. HC ═ O in cinnamic aldehyde at 1672cm^-1The characteristic peak is obviously weakened, which shows that HC ═ O of cinnamaldehyde and-NH on chitosan₂And (4) reacting.

Example 7

Drug Loading (LC) and Encapsulation Efficiency (EE) were determined as follows

EE (%) ═ total amount of drug in ENR-NPs/total amount of drug added X100

LC (%) ═ total amount of drug in ENR-NPs/total weight of ENR-NPs × 100

10mg of each of the ENR-NPs prepared in examples 1 to 3 was dispersed in a 100mL volumetric flask containing a hydrochloric acid solution having a pH of 1.0, and stirred for 24 hours, centrifuged at 12000rpm for 30 minutes, and then the absorbance intensity of the supernatant was measured at 335nm with a UV-visible spectrophotometer to calculate the actual enrofloxacin content (the enrofloxacin concentration in the ENR-NPs was calculated from the linear relationship between the absorbance intensity and the enrofloxacin concentration in the hydrochloric acid solution having a pH of 1.0).

The results of the drug Loading (LC) and Encapsulation Efficiency (EE) measurements are shown in table 1, and it can be seen that an average enrofloxacin encapsulation efficiency of 76.6% and an average drug loading of 3.3% indicate potential applications thereof.

TABLE 1 drug loading and encapsulation efficiency of ENR-NPs

Example 8

Morphology of ENR-NPs

As shown in FIG. 4, Transmission Electron Microscopy (TEM) recorded morphological features of ENR-NPs. TEM images of ENR-NPs showed a uniform solid spherical structure of nanoparticles 120nm in diameter and good monodispersity.

As shown in FIG. 5, Dynamic Light Scattering (DLS) analysis of the particle size distribution of ENR-NPs revealed that the average ENR-NPs diameter was (135.00. + -. 16.94nm) according to the size indicated by TEM. This may occur due to the swelling effect of ENR-NPs during the preparation of DLS liquid samples.

As shown in FIG. 6, the zeta potential of ENR-NPs was 3.52. + -. 4.65 mV.

As shown in fig. 7, after ENR-NPs were treated at 37 ℃ at pH 5.0 for 12 hours, corrosion and aggregation occurred due to their acid-sensitive potential.

Example 9

In vitro Release study of ENR-NPs

The pH-dependent release curve of ENR-NPs in PBS solution is shown in FIG. 8, and it can be seen that enrofloxacin is released faster within the first 120 minutes, and the blood concentration in vivo can reach the therapeutic concentration quickly after administration. But the drug release rate gradually decreased after 120min and continued to be slowly released over the next 10 hours. After the therapeutic concentration is reached, the blood concentration lost due to metabolism can be continuously and slowly supplemented, so that the therapeutic time of the medicine is prolonged, and the final period of multiple administration is avoided.

Comparative analysis of drug release rates of ENR-NPs at pH 7.4, pH 6.0 and pH 5.0 revealed that acidity of the release medium had a significant effect on the release rate of enrofloxacin. The drug cumulative release rate of ENR-NPs reached 88.12% at pH 5.0, and only 35.41% at pH 7.4. The result shows that the enrofloxacin is not easy to release when the ENR-NPs are in a neutral environment, so that the possibility of drug resistance of bacteria is greatly reduced; meanwhile, the ENR-NPs can realize the quick release of the enrofloxacin in a weak acid environment, which shows that the ENR-NPs have good pH response sensitivity.

Non-oral administration of ENR-NPs for the treatment of bacterial infections is readily spread and distributed in tissues due to their nanoscale structure and low release rate at body pH levels. As the bacteria multiply and grow, the local environment of the infected area becomes acidic. When the ENR-NPs penetrate the infected area, the spherical structure of the ENR-NPs is eroded, as shown in figure 7, and the coated enrofloxacin is released, thereby achieving the aim of targeted drug delivery of bacteria. In contrast, when ENR-NPs are used as an oral administration system (DDS), the release rate of enrofloxacin is reduced to 2.58% within 5 minutes due to the neutral environment of the oral cavity, so that the stimulation of enrofloxacin to taste buds is prevented, and similarly, when the ENR-NPs enter the acidic environment (the pH value range is 1-3) of the stomach, the medicine is quickly released, so that the purpose of timely treatment is achieved.

The above results indicate that ENR-NPs can achieve the purpose of pH triggered drug delivery for on-demand bacterial infection treatment during non-oral administration or to mask the strong bitter taste of enrofloxacin upon oral administration.

Example 10

In vitro antibacterial Activity of ENR-NPs

In vitro antibacterial activity of ENR-NPs against Staphylococcus aureus after 16 hours incubation of the plates, as shown in FIG. 9. In the figure, a is the inhibition zone of enrofloxacin with pH value of 7.4; b is the inhibition zone of ENR-NPs with the pH value of 7.4; c is the inhibition zone of enrofloxacin with pH value of 5.0; d is the inhibition zone of ENR-NPs with the pH value of 5.0. a. The diameters of the inhibition zones of staphylococcus aureus of b, c and d are shown in table 2. The larger inhibition zone (a) shows that the antibacterial activity of enrofloxacin on staphylococcus aureus under the condition of pH 7.4 is slightly stronger than that of the inhibition zone (c) under the condition of pH 5.0. Due to its low release rate in a neutral environment, the inhibition zone (b) of ENR-NPs observed at pH 7.4 was much smaller than that of enrofloxacin under the same conditions. However, the diameter of the inhibition zone (d) of the ENR-NPs at pH 5.0 is obviously larger than that of the inhibition zone (c) of the ENR-NPs at pH 5.0, which shows that the stronger the acidic condition is, the more the ENR-NPs release the drug, and confirms the pH response characteristic of the ENR-NPs.

TABLE 2 Staphylococcus aureus zone diameter

While the present invention has been described in considerable detail and with particular reference to a few illustrative embodiments thereof, it is not intended to be limited to any such details or embodiments or any particular embodiments, but it is to be construed as effectively covering the intended scope of the invention by providing a broad, potential interpretation of such claims in view of the prior art with reference to the appended claims. Furthermore, the foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalent modifications thereto.