[Recent progress of chromatographic techniques for antibody purification].

Antibody drugs are becoming increasingly popular in disease diagnosis, targeted therapy, and immunoprevention owing to their characteristics of high targeting ability, strong specificity, low toxicity, and mild side effects. The demand for antibody drugs is steadily increasing, and their production scale is expanding. Upstream cell culture technology has been greatly improved by the high-capacity production of monoclonal antibodies. However, the downstream purification of antibodies presents a bottleneck in the production process. Moreover, the purification cost of antibodies is extremely high, accounting for approximately 50%-80% of the total cost of antibody production. Chromatographic technology, given its selectivity and high separation efficiency, is the main method for antibody purification. This process usually involves three stages: antibody capture, intermediate purification, and polishing. Different chromatographic techniques, such as affinity chromatography, ion-exchange chromatography, hydrophobic interaction chromatography, mixed-mode chromatography, and temperature-responsive chromatography, are used in each stage. Affinity chromatography, mainly protein A affinity chromatography, is applied for the selective capture and purification of antibodies from raw biofluids or harvested cell culture supernatants. Other chromatographic techniques, such as ion-exchange chromatography, hydrophobic interaction chromatography, and mixed-mode chromatography, are used for intermediate purification and antibody polishing. Affinity biomimetic chromatography and hydrophobic charge-induction chromatography can produce antibodies with purities comparable with those obtained through protein A chromatography, by employing artificial chemical/short peptide ligands with good selectivity, high stability, and low cost. Temperature-responsive chromatography is a promising technique for the separation and purification of antibodies. In this technique, antibody capture and elution is controlled by simply adjusting the column temperature, which greatly eliminates the risk of antibody aggregation and inactivation under acidic elution conditions. The combination of different chromatographic methods to improve separation selectivity and achieve effective elution under mild conditions is another useful strategy to enhance the yield and quality of antibodies. This review provides an overview of recent advances in the field of antibody purification using chromatography and discusses future developments in this technology.

Synthesis of hierarchically porous zirconium-based metal-organic framework@silica core-shell stationary phase through etching strategy for liquid chromatography.

Metal organic frameworks (MOFs) show promise to be employed as stationary phase for high performance liquid chromatography (HPLC), however, the microporous structures of MOFs seriously restrict the diffusion and mass transfer of solute molecules, leading to a low column efficiency. In this paper, the fabrication of hierarchically porous UiO-66@SiO2 (HP- UiO-66@SiO2) core-shell microspheres via H2O2 etching has been proposed as a viable approach to enhance the separation performance of MOFs-based columns for HPLC. Through the direct treatment of the preliminary prepared UiO-66@SiO2 microspheres with H2O2 etching, HP-UiO-66@SiO2 core-shell microspheres were successfully synthesized with an enlarged pore size of up to 9 nm, facilitating efficient mass transfer in chromatographic separation. The prepared HP-UiO-66@SiO2 core-shell microspheres were then explored as stationary phase in HPLC to separate the nonpolar alkyl benzene homologues, the polar aromatic alcohol homologues and the xylene isomers. The results indicated that the baseline separations of these solutes were achieved successfully with narrow peak width and higher resolution than the UiO-66@SiO2 column. The HP-UiO-66@SiO2 column exhibited superior separation performance, reaching a maximum plate number of 134,459/m for fluorene, and showing good reproducibility. As a result, this template-free approach suggests that the fabrication of hierarchically porous MOFs@silica core-shell microspheres is a successful approach to enhance the column efficiency of MOFs-based columns in HPLC.

Redispersible Reduced Graphene Oxide Prepared in a Gradient Solvent System.

We designed a gradient solvent strategy for the reduction of graphene oxide, matching the hydrophilic properties of graphene oxide (GO) and reduced graphene oxide (RGO), respectively. A third solvent was added dropwise to regulate the hydrophilic variation of the continuous gradient system which maintained the whole reduction process without aggregation, and the obtained RGO dispersions could maintain stability for a long time. The separated RGO solid powder can be directly ultrasonically redispersed in N-methyl-pyrrolidone (NMP) with an average particle size as low as 200 nm. Furthermore, RGO with a high C/O ratio of 13.75 was prepared on the basis of the gradient solvent system. Using different structures of dispersants and polymers as representatives, we employed successive solvent rinsing, thermal solvent extraction, and thermal treatment to study adsorption and desorption. It was found that the above measures differed significantly in the removal of surface sorbates. The selected fatty alcohol polyoxyethylene ether (AEO) series achieved a good balance between the system dispersion and surface adsorbate removal. The conductivity was originally 5236 S m-1, and it increased from 9024 to 18,000 S m-1 after thermal treatment at 300 and 500 °C, respectively.

Synthesis and application of 5 µm monodisperse porous silica microspheres with controllable pore size using polymeric microspheres as templates for the separation of small solutes and proteins by high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) is a powerful tool to separate and analyze complex samples. Monodiseperse porous silica microspheres (MPSMs) have been widely used as column packings in HPLC. However, synthesis of MPSMs with controllable sizes of both particles and pores for the separation of small solutes and proteins in HPLC still remains a challenge. In this paper, an effective and facile approach to prepare MPSMs with controllable particle size and pore size by using porous polymer microspheres as templates is presented. By employing porous PGMA/EDMA microspheres as templates and tetraethyl orthosilicate (TEOS) as the silica source, 5 µm MPSMs with tunable pore sizes were synthesized successfully. The as-prepared MPSMs were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), dynamic laser scattering, and mercury intrusion porosimetry. The results indicated that the MPSMs obtained retained the original size of the polymer templating particles and calcination caused almost no shrinkage. Furthermore, the effects of the pore size of polymer template microspheres, different amino-functionalizations of PGMA/EDMA microspheres and the mass ratio of PGMA/EDMA microspheres/TEOS on the pore size of MPSMs were carefully studied. The results indicated that the pore size of MPSMs was adjusted from 20 to 69 nm by controlling the pore size of the polymer microspheres and the mass ratio of PGMA/EDMA microspheres/TEOS in the sol-gel process. In addition, the amino-functionalization of PGMA/EDMA microspheres with different structure-directing agents, such as (3-aminopropyl)triethoxysilane (APTES), trimethylamine hydrochloride (TMA) and tetraethylenepentamine (TEPA), also resulted in MPSMs with the different pore sizes. MPSMs with large pore sizes of more than 30 nm were fabricated by using TEPA-functionalized PGMA/EDMA microspheres as templates, while with TMA-functionalized PGMA/EDMA microspheres as templates, MPSMs with pore sizes of approximately 10 nm were obtained. The as-prepared MPSMs were further modified with different silanes, such as C4, C8 and C18, to explore as stationary phases for the separation of proteins and small solutes in reversed phase liquidi chromatography (RPLC). The results illustrated that the baseline separation of 7 kinds of proteins could be achieved based on MPSMs with pore sizes of 30 nm, and 6 kinds of alkyl benzenes and 5 kinds of aromatic alcohol homologs could be separated completely based on MPSMs with pore sizes of 11 nm. This work demonstrated that MPSMs prepared by applying the polymer templating method showed a promising potential applicability in HPLC.

[Research on intelligent controlled drug delivery with polymer].

The intelligent controlled drug delivery systems are a series of the preparations including microcapsules or nanocapsules composed of intelligent polymers and medication. The properties of preparations can change with the external stimuli such as pH value, temperature, chemical substance, light, electricity and magnetism. According to this properties, the drug delivery can be intelligently controlled. This paper has reviewed research on syntheses and applications of intelligent controlled drug delivery systems with polymers.

[The advance in researches for biomedical intelligent polymer materials].

The properties of biomedical intelligent polymer materials can be changed obviously when there is a little physical or chemical change in external condition. They are in the forms of solids, solutions and polymers on the surface of carrier, including aqueous solution of hydrophilic polymers, cross-linking hydrophilic polymers (i.e. hydrogels) and the polymers on the surface of carrier. In this paper are reviewed the progress in researches and the application of biomedical intelligent polymer materials.