Trimer Affibody Protein PET Imaging Agent for PDGFR-β Targeting
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Solution Overview
Problem
Existing PET imaging agents using targeting biomolecules like polypeptides and monoclonal antibodies face issues with affinity, stability, and prolonged circulation times, which hinder effective diagnosis of diseases such as tumors and fibrosis.
Innovation Solution
A gallium 68 labeled PDGFR-β targeting trimer affibody protein with a unique amino acid sequence, specifically the Z-tri protein, is developed, which offers high affinity and stability, and is efficiently labeled with gallium 68 for PET imaging, utilizing a method involving a DOTA bifunctional chelating agent and a PD-10 desalting column for purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dimer affibody structure is used to improve affinity constant, then the affinity to PDGFR-β is improved, but the in vivo stability deteriorates due to dependence on disulfide bonds
Solution Approach 1:
The dimer affibody structure is segmented into two independent monomer units connected by a flexible linker peptide rather than disulfide bonds. This segmentation allows each monomer to independently bind PDGFR-β while the flexible linker provides structural stability in vivo without relying on labile disulfide bonds, thus resolving the contradiction between affinity and stability.
2Ease of manufacture
If a monomer affibody is used to simplify structure, then ease of manufacture is improved, but affinity constant deteriorates
Solution Approach 1:
Two monomer affibody units are merged into a dimer structure through a flexible linker peptide. This merging maintains the simplicity of monomer production while achieving enhanced affinity through bivalent binding to PDGFR-β, thus resolving the contradiction between ease of manufacture and affinity.
3Reliability
If monoclonal antibody is used to improve affinity, then binding capability is improved, but circulation time deteriorates due to prolonged elimination time
Solution Approach 1:
The affibody molecule is designed as a small, short-lived protein alternative to monoclonal antibodies. Despite its smaller size and shorter half-life, it achieves comparable binding capability through high-affinity PDGFR-β targeting. The short circulation time is actually advantageous for PET imaging as it reduces background signal and allows faster clearance, resolving the contradiction between binding capability and circulation time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The gallium 68 labeled affibody protein achieves high nuclide labeling rates and effective PET imaging of tumors and fibrotic diseases, with improved stability and targeting capabilities compared to monomer and dimer affibody structures, demonstrating enhanced imaging efficacy.
Implementation Method 1
adding a tetraazacyclododecane-tetraacetic-acid (DOTA) bifunctional chelating agent for coupling
Implementation Method 2
using a PD-10 desalting column to remove uncombined DOTAs
Implementation Method 3
using a PD-10 desalting column to remove uncombined DOTAs, and obtaining the successfully coupled DOTA-Z-tri protein
Implementation Method 4
slowly adding 68GaCl3leacheate to the protein solution according to a ratio for reaction, so as to obtain 68Ga-Z-tri
Data Source
AI summary
Disclosed are a gallium 68 labeled affibody protein PET imaging agent and a use thereof; the imaging agent comprises 68Ga-Z-tri; the 68Ga-Z-tri is obtained by labeling an affibody protein with gallium 68; the affibody protein comprises a PDGFR-β targeting trimer affibody protein Z-tri; and the amino acid sequence listing of the affibody protein Z-tri is as shown in SEQ ID NO. 1. According to the present invention, the utilized PDGFR-β targeting trimer affibody having a unique amino acid sequence has the characteristics of high affinity and high stability compared with a monomer affibody and a dimer affibody, can greatly increase a nuclide labeling rate, and achieves the effectiveness thereof as a PET imaging probe.