Smart and biofunctional streptavidin

Live Macrophage-Delivered Doxorubicin-Loaded Liposomes Effectively Treat Triple-Negative Breast Cancer

Triple-negative breast cancer is often aggressive and resistant to various cancer therapies, especially corresponding targeted drugs. It is shown that targeted delivery of chemotherapeutic drugs to tumor sites could enhance treatment outcome against triple-negative breast cancer. In this study, we exploited the active tumor-targeting capability of macrophages by loading doxorubicin-carrying liposomes on their surfaces via biotin-avidin interactions. Compared with conventional liposomes, this macrophage-liposome (MA-Lip) system further increased doxorubicin accumulation in tumor sites, penetrated deeper into tumor tissue, and enhanced antitumor immune response. As a result, the MA-Lip system significantly lengthened the survival rate of 4T1 cell-bearing mice with low toxicity. Besides, the MA-Lip system used highly biocompatible and widely approved materials, which ensured its long-term safety. This study provides a system for triple-negative breast cancer treatment and offers another macrophage-based strategy for tumor delivery.

Pretargeted radioimmunotherapy using genetically engineered antibody-streptavidin fusion proteins for treatment of non-hodgkin lymphoma

PURPOSE

Pretargeted radioimmunotherapy (PRIT) using streptavidin (SAv)-biotin technology can deliver higher therapeutic doses of radioactivity to tumors than conventional RIT. However, "endogenous" biotin can interfere with the effectiveness of this approach by blocking binding of radiolabeled biotin to SAv. We engineered a series of SAv FPs that downmodulate the affinity of SAv for biotin, while retaining high avidity for divalent DOTA-bis-biotin to circumvent this problem.

EXPERIMENTAL DESIGN

The single-chain variable region gene of the murine 1F5 anti-CD20 antibody was fused to the wild-type (WT) SAv gene and to mutant SAv genes, Y43A-SAv and S45A-SAv. FPs were expressed, purified, and compared in studies using athymic mice bearing Ramos lymphoma xenografts.

RESULTS

Biodistribution studies showed delivery of more radioactivity to tumors of mice pretargeted with mutant SAv FPs followed by (111)In-DOTA-bis-biotin [6.2 ± 1.7% of the injected dose per gram (%ID/gm) of tumor 24 hours after Y43A-SAv FP and 5.6 ± 2.2%ID/g with S45A-SAv FP] than in mice on normal diets pretargeted with WT-SAv FP (2.5 ± 1.6%ID/g; P = 0.01). These superior biodistributions translated into superior antitumor efficacy in mice treated with mutant FPs and (90)Y-DOTA-bis-biotin [tumor volumes after 11 days: 237 ± 66 mm(3) with Y43A-SAv, 543 ± 320 mm(3) with S45A-SAv, 1129 ± 322 mm(3) with WT-SAv, and 1435 ± 212 mm(3) with control FP (P < 0.0001)].

CONCLUSIONS

Genetically engineered mutant-SAv FPs and bis-biotin reagents provide an attractive alternative to current SAv-biotin PRIT methods in settings where endogenous biotin levels are high.

A Brief Introduction to the Streptavidin-Biotin System and its Usage in Modern Surface Based Assays

This review presents the molecular basis of the high affinity between (strept)avidin and biotin as it was discovered from different protein crystal structures using wild type and mutant streptavidin. Optimization strategies for further improving the applicability of the (strept)avidin-biotin system and prospects for modulating the affinity are discussed. The characterization and the application of the streptavidin-biotin system in surface-based biosensing assays are demonstrated with selected examples focussing on surface plasmon resonance (SPR) and atomic force microscopy (AFM). Recent trends to further enhance the utility of convential SPR e.g. parallel detection of biological molecules and sensitivity enhancement towards small molecules are covered as well.

Protein Immobilization on Aminated Poly(glycidyl methacrylate) Nanofibers as Polymeric Carriers

Recently, protein carriers based on nanomaterials have been highlighted in diverse biological applications such as protein extraction, separation, and delivery due to their facile gravimetric sedimentation in the aqueous phase and abundant surface functionalities, which were used as anchoring sites for proteins. From this viewpoint, poly(glycidyl methacrylate) nanofibers (PGMA NFs) can be an excellent candidate for protein support because PGMA NFs possess the activated epoxide functional groups on the surface. In addition, cured PGMA NFs (PGMA-NH2 NFs) reveal different surface functionalities such as primary amine groups. They can be linked with carboxylated proteins. Ferritin and streptavidin were selected as models of the pristine and biolinker-mediated proteins in this experiment and immobilized onto PGMA NFs and aminated PGMA-NH2 NFs. The successful conjugations of ferritin and streptavidin were confirmed with transmission electron microscopy and fluorescein-isothiocyanate-tagged molecules. Protein immobilization using the pristine and the cured PGMA NFs could be considered as an outstanding protocol for facile protein delivery.

Immobilized iminobiotin on magnetic poly (vinyl alcohol) microspheres for single-step purification of streptavidin

Magnetic poly (vinyl alcohol) microspheres (MPVAMS) immobilized with iminobiotin as the ligand were prepared for the purification of streptavidin. Parameters of magnetic separation, including spacers, NHS-iminobiotin added, elution behavior, and sample treatment, were optimized to improve the purification efficiency to achieve the maximum recovery of the protein. Streptavidin was successfully purified 38-fold from culture supernatant in a single-step by iminobiotin-MPVAMS with an overall recovery of 90.15% and purity of 95.08%. Hence, this study effectively illustrated the favorable application of magnetic microcarriers for the purification of streptavidin.

Custom design of the cardiac microenvironment with biomaterials

Many strategies for repairing injured myocardium are under active investigation, with some early encouraging results. These strategies include cell therapies, despite little evidence of long-term survival of exogenous cells, and gene or protein therapies, often with incomplete control of locally-delivered dose of the factor. We propose that, ultimately, successful repair and regeneration strategies will require quantitative control of the myocardial microenvironment. This precision control can be engineered through designed biomaterials that provide quantitative adhesion, growth, or migration signals. Quantitative timed release of factors can be regulated by chemical design to direct cellular differentiation pathways such as angiogenesis and vascular maturation. Smart biomaterials respond to the local environment, such as protease activity or mechanical forces, with controlled release or activation. Most of these new biomaterials provide much greater flexibility for regenerating tissues ex vivo, but emerging technologies like self-assembling nanofibers can now establish intramyocardial cellular microenvironments by injection. This may allow percutaneous cardiac regeneration and repair approaches, or injectable-tissue engineering. Finally, materials can be made to multifunction by providing sequential signals with custom design of differential release kinetics for individual factors. Thus, new rationally-designed biomaterials no longer simply coexist with tissues, but can provide precision bioactive control of the microenvironment that may be required for cardiac regeneration and repair.

Avidin related protein 2 shows unique structural and functional features among the avidin protein family

Background

The chicken avidin gene family consists of avidin and several avidin related genes (AVRs). Of these gene products, avidin is the best characterized and is known for its extremely high affinity for D-biotin, a property that is utilized in numerous modern life science applications. Recently, the AVR genes have been expressed as recombinant proteins, which have shown different biotin-binding properties as compared to avidin.

Results

In the present study, we have employed multiple biochemical methods to better understand the structure-function relationship of AVR proteins focusing on AVR2. Firstly, we have solved the high-resolution crystal structure of AVR2 in complex with a bound ligand, D-biotin. The AVR2 structure reveals an overall fold similar to the previously determined structures of avidin and AVR4. Major differences are seen, especially at the 1–3 subunit interface, which is stabilized mainly by polar interactions in the case of AVR2 but by hydrophobic interactions in the case of AVR4 and avidin, and in the vicinity of the biotin binding pocket. Secondly, mutagenesis, competitive dissociation analysis and differential scanning calorimetry were used to compare and study the biotin-binding properties as well as the thermal stability of AVRs and avidin. These analyses pinpointed the importance of residue 109 for biotin binding and stability of AVRs. The I109K mutation increased the biotin-binding affinity of AVR2, whereas the K109I mutation decreased the biotin-binding affinity of AVR4. Furthermore, the thermal stability of AVR2(I109K) increased in comparison to the wild-type protein and the K109I mutation led to a decrease in the thermal stability of AVR4.

Conclusion

Altogether, this study broadens our understanding of the structural features determining the ligand-binding affinities and stability as well as the molecular evolution within the protein family. This novel information can be applied to further develop and improve the tools already widely used in avidin-biotin technology.