Modification of zein functional drug-loaded microsphere with TRIS

As a common biological buffer, Tris(Hydroxymethyl)Aminomethane (TRIS) is not only widely used as a solvent for nucleic acids and proteins, but also as one of the main components of protein electrophoresis buffers. It can also produce a variety of chemicals and pesticides, pharmaceutical products, and it is an important intermediate for the preparation of surfactants, vulcanization accelerators and some drugs. This article will introduce another role of TRIS——modified zein functional drug-loaded microspheres.

As a natural hydrophobic macromolecule, zein has a wide range of sources, it is non-toxic, non-immunogenic, and has good biocompatibility and biodegradability. It is one of the few hydrophobic biopolymers that are allowed to be taken orally by the FDA：

(1) Its amino acid composition is very special, the proportion of non-polar amino acids is more than 50%. It can embed various substances such as polysaccharides. DNA, RNA, proteins, metal nanoparticles, quantum dots, oil droplets, and hydrophobic drugs;

(2) The amino acid residues on zein carry certain polar groups (such as ‐SH, ‐COOH, ‐NH3, and ‐OH), it provides the possibility to graft various functional molecules for chemical reaction sites and adapt to the complex and varied human environment.

Therefore, zein is an advantageous drug carrier material. However, the proportion of sulphur-containing amino acids in zein is only 2.8%, the ratio of basic amino acids is only 2.9%, and the proportion of hydroxyamino acids is 13.4%, which limits the selection of functional molecules and the effect of modification. To improve this, the researchers modified it with TRIS, including the following steps [1]:

(1) The zein and the amino protecting agent di-tert-butyl dicarbonate are dissolved in a specific dimethyl sulfoxide or ethanol aqueous solution at a mass ratio of 1:1~1.5:1, and protected from light at 25~40°C. The reaction is carried out for 12~24 hours to obtain a zein protection solution;

(2) Under the protection of nitrogen, add carbodiimide salt, N-hydroxysuccinimide and TRIS (CAS 77-86-1) to the zein protection solution, and avoid the light reaction at 25-40°C for 12~24 hours. To obtain a TRIS-zein solution;

(3) under the protection of nitrogen, adding concentrated hydrochloric acid to the tris-zein solution, and avoiding light reaction at 25-40°C for 6-8h;

(4) adjusting the pH to 5.0~6.0, transferring to a dialysis bag, centrifuging the retained solution in the dialysis bag, and lyophilizing to obtain TRIS-zein;

(5) Dissolving the hydrophobic drug and the lyophilized TRIS -zein in an aqueous solution of ethanol at a mass ratio of 1:1 to 1:10; and injecting hydrochloric acid having a pH of 2.5 to 4.5 under magnetic stirring. In the aqueous solution, after stabilization, the supernatant is centrifuged to obtain a drug-loaded microsphere;

(6) Functional modification of drug-loaded microspheres: separately prepare solutions containing different functional molecules, disperse the drug-loaded microspheres into a solution containing functional molecules, stir the reaction, centrifuge to remove the supernatant, and obtain functional drug carrying microsphere. The drug microspheres have a particle size of 100~300 nm and a drug-loading efficiency of 81.48~86.01%, and the grafting amount of the functional molecules is 1.72~1.94 times that of the unmodified zein microspheres.

The coupling of TRIS to zein significantly improves the physicochemical properties of zein. The prepared microspheres have good sphericity, uniform particle size distribution, high drug-loading efficiency, and are suitable for in vivo delivery. This research expands the application of zein in drug delivery systems and has a good application prospect in the field of medicine.

References

[1] Jiang Yanbin, Pang Jiafeng, Lu Shan, Li Zhixian, Trimethylolamine modified zein functional drug-loaded microspheres and preparation method. 2018, CN108403662A.

Edited by Suzhou Yacoo Science Co., Ltd.

TRIS, Bis-Tris, Tricine, TES, TAPS, What is the difference in application?

TRIS(Tris(Hydroxymethyl)Aminomethane), Bis-Tris, Tricine, TES, TAPS are buffers commonly used in biochemical experiments and molecular biology experiments, and they all contain the structure of TRIS. Then what are the differences in application between these buffers?

We hope that the following table could solve your doubts.

Table 1. The application of TRIS, Bis-Tris, Tricine, TES, TAPS

In specific use, buffers containing the TRIS (CAS：77-86-1) structure will form a strong or weak complex with a variety of metal ions, so the stability constant should be taken into account. In addition, the buffer range and the appropriate type of experiment also should be considered in order to obtain the best experimental results.

Edited by Suzhou Yacoo Science Co., Ltd.

For the preparation of Coatings？The role of TRIS you may not know!

As we all know, Tris(Hydroxymethyl)Aminomethane (TRIS) is not only widely used as a buffer for biological and chemical experiments, but also as solvent for nucleic acids and proteins, intermediates of surfactants, pesticide and drugs. But today, we will introduce the application of TRIS you may not know——For the preparation of Coatings.

TRIS (THAM) plays four main roles in the preparation of the coating: pH regulator, crosslinking accelerators, polyester coating materials and phase change cores.

1. pH Regulator

The effective buffering range of TRIS buffer is pH 7.0~9.2. Yuan et al. [1] invented a non-yellowing polyester coating with best pH value of 7.5~8.5 in the preparation. Researchers used TRIS buffer to adjust the pH value. The prepared product had good adhesion and scratch resistance, and it will not significantly yellowed after high temperature operation or aging.

2. Crosslinking Accelerator

Crosslinking accelerators can act as bridging molecules between linear molecules, so that multiple linear molecules are bonded to each other to form a network structure. Polyhydric alcohols are often used as external crosslinks in the preparation of coatings. Zhang Jianwei et al. [2] invented a silane modified polyurethane glass coating with TRIS as a cross-linking promoter. Which can be operated in the air at room temperature for 40min without obvious thickening phenomenon.

3. Polyester Coating Materials

Polyhydric alcohols, polyacids, catalysts and antioxidants can be used as a coating composition. Deng Mujian et al. [3] used TRIS as the polyhydric alcohols to react with the polybasic acid or anhydride terephthalic acid or isophthalic acid, to obtain an outdoor dry blending powder coating polyester resin.

4. Phase Transition Core

When the temperature reaches the phase transition temperature, the structure of the polyol phase transition material will change from the layered body-centered structure to the isotropic facial-centered structure, and the hydrogen bonds between the layers are broken, molecules change from crystalline to amorphous, and release bond energy. It has the advantage of large enthalpy of phase change, stable performance, long service life. Gao Hongyi et al. [4] used the polyol characteristics of TRIS as a phase change core to prepare an airgel based phase transition coating.

TRIS (CAS 77-86-1) is not only an important biological buffer, but also an important material for organic synthesis. Although the application in the field of coatings is not very extensive, but with the development of science and technology, we believe that TRIS will get more applications in this area in the future.

References

[1] San C. Yuan, Mitchell S. Chinn. Non-yellowing polyester coating composition. US 7,087,672 B2, August 8, 2006.

[2] Zhang Jianwei, Du Houjun, Wang Yudong, et al. Silane modified polyurethane glass primer and preparation method. CN 102516921 B, 2013, 10, 02.

[3] Deng Mujian, Zhang Liangfu, Cao Yongyi, and so on. Preparation of polyester resin for outdoor dry blending powder coating. CN 102719180, 2012, 10, 10.

[4] Gao Hongyi, Feng Yanhui, Zhou Xiaofei. A preparation method of air-gel-based thermal phase transition coating. CN 105199472, 2015, 12, 30.

Edited by Suzhou Yacoo Science Co., Ltd.

Is HEPES suitable for the in vitro testing of inorganic biomaterials in SBF?

Recently, much work has focused on the development of inorganic materials in bone tissue engineering, such as glass and glass scaffolds. These inorganic materials classified as “bioactive” should first pass an in vitro test in simulated body fluid (SBF).In the test, an inert buffer to keep neutral pH is necessary to maintain conditions close to those in blood plasma. According to an international standard (ISO:23317:2014) for the test, Tris(hydroxymethyl)aminomethane is using to maintain neutral pH in SBF.

In 2011, Rohanova et al. found that TRIS buffer used with a highly reactive glass-ceramic scaffold accelerates the dissolution of the glass-ceramic crystalline phase and lead to the formation of hydroxyapatite. It demonstrates that TRIS buffer is not suitable for in vitro testing. So other alternatives must be sought.

Rohanova et al. evaluated whether would HEPES buffer be more suitable for SBF. They studied the interaction of HEPES buffer with the glass-ceramic scaffold (45S5 bioactive glass-based) through comparing SBF with HEPES and demineralized water with HEPES. The tested scaffold was exposed to the media under a static-dynamic arrangement for 15 days. Leachate samples were collected daily for analysis Ca²⁺ ions and Si, (PO₄)^3- ions, and to measure pH. The glass-ceramic scaffold was analyzed by SEM/EDS, XRD, and WD-XRF before and after 0.3,1,3,7,11,15 days of exposure. Their results confirmed the rapid selective dissolution of the glass-ceramic crystalline phase containing Ca²⁺ ions due to the presence of HEPES, hydroxyapatite supersaturation being reached within 24 h in both solutions. These results suggest that HEPES is also not suitable for the in vitro testing of highly reactive inorganic biomaterials (glass, glass-ceramics).

In a word, findings of Rohanova et al. show that TRIS and HEPES buffers are not suitable to maintain the neutral pH for the in vitro testing. Consequently, researcher will work further to test other buffers to find suitable alternatives.

Edited by Suzhou Yacoo Science Co., Ltd.