Biocompatible post-polymerization functionalization of a water soluble poly(p-phenylene ethynylene)

Abstract

A biocompatible post-polymerization functionalization reaction takes advantage of a polymer's structural motif for the controllable attachment of biotin as a model biosensor that responds to streptavidin. 10Strategies for the post-polymerization functionalization (PPF) of polymers are advantageous in that they allow for tuning of a polymer's properties without synthetically retreating to the monomer stage. Further, PPF permits the incorporation of functional groups that may be incompatible with 15 polymerization conditions. Several strategies have been reported for conjugated polymers. A number of designs involve substitution reactions with pendant halogen, 1 alcohol, 2 or carboxylic acid moieties, 3 and application of high yielding click chemistries 4 like the 1,3-dipolar cycloaddtion of alkynes 20 and azides 5 or thiol-conjugate addition 6 have also been reported. Two potential drawbacks are characteristic of the above strategies: (i) an appropriately functionalized monomer specific for the intended PPF must be incorporated into the polymer synthesis--often in protected form and (ii) it can be 25 difficult to control the extent of functionalization.We recently reported the synthesis of a rigid hydrophilic monomer (1) that--when incorporated into poly(p-phenylene ethynylenes) (PPEs) 7 (P1)--leads to increased spectral purity 30 by preventing hydrophobically induced aggregate emission. 8 We envisioned that the three dimensional array of vicinal hydroxyl groups might be further elaborated through periodate oxidation and reductive amination (P1→2→3, Scheme 1). 9 Similar processes have been widely applied for 35 bioconjugation through periodate oxidation of carbohydrate residues, making this process compatible with existing bioconjugation schemes. Herein we report a biocompatible post-polymerization biotinylation of P1, where (i) the need for a PPF specific monomer is negated by activation of an 40 existing structural motif, and (ii) the extent of functionalization can be controlled by the equivalents of the NaIO 4 reagent. Further, the improved spectral purity imparted by the presence of 1 in 3a is not lost. In turn, this demonstrates an improved signal amplified biosensor 10 45 response to fluorophore-labeled streptavidin, a tetrameric protein with high biotin affinity (4 x 10 -14 M) 11 that has been applied to a variety of conjugated polymer affinitychromic 3,12 and agglutination 2b biosensor designs. 50Scheme 1 Periodate oxidative activation and reductive amination Treatment of P1 with 0.2 equivalents of NaIO 4 in water generated 1,6-dialdehyde moieties at random positions along the backbone (2, Scheme 1). 13 Subsequent incubation with an excess of amine-containing compound (a or b) in aqueous 55 alkaline solution generated the putative Schiff base, which was reduced in situ to the tertiary amine 3 with NaCNBH 3 (vide infra, Scheme 2).The azepane linkage in 3 is proposed based on two model studies. Firstly, the broad nature of the 1 H NMR signals of 3a 60 overlapped with the weaker biotin signals making dete...

Functionalized Conjugated Polyelectrolytes for Biological Sensing and Imaging

“…For example, Bunz et al . prepared a monomer (Scheme a) with two side chains carrying triisopropylsilane (TIPS) protected alkyne groups 18c. Copolymerization between this monomer and diethyl 2,2′‐((2,5‐diiodo‐1,4‐phenylene)bis(oxy))diacetate furnished a CP, which was deprotected in situ using tetrabutylammonium fluoride (TBAF) and coupled with mannose azide derivative using CuSO 4 /Na‐ascorbate (to generate Cu(I)) as the catalyst in THF, followed by carboxyl group deprotection in NaOH aqueous solution to yield 12 .…”

“…Copolymerization between this monomer and diethyl 2,2′‐((2,5‐diiodo‐1,4‐phenylene)bis(oxy))diacetate furnished a CP, which was deprotected in situ using tetrabutylammonium fluoride (TBAF) and coupled with mannose azide derivative using CuSO 4 /Na‐ascorbate (to generate Cu(I)) as the catalyst in THF, followed by carboxyl group deprotection in NaOH aqueous solution to yield 12 . Our group adopted a prepolymerization approach to synthesize a mannose‐substituted CP 18b. By reacting alkyl bromide with sodium azide, we obtained a fluorene monomer, with each chain having an azide group (Scheme b).…”

“…The same group subsequently synthesized a new biotinylated PPE 23 (Scheme a) via a postpolymerization method 18a. Its parental polymer 22 (Scheme a) has three‐dimensional arrays of vicinal hydroxyl groups around the backbone, which effectively mitigate the CP‐backbone assembly to reduce the aggregation‐induced self‐quenching.…”

“…Therefore, it has been used as a model protein for the study of mannose‐lectin interactions. We constructed an intelligent bi‐component FRET probe using mannose‐substituted 24 and neutral conjugated oligomer 25 (Figure a) to realize highly selective, label‐free, naked‐eye detection of Con A 18b . 24 was synthesized by Suzuki coupling of the mannose‐substituted monomer (Scheme b) and 2,2′‐(9,9‐bis(2‐(2‐(2‐bromoethoxy)ethoxy)ethyl)‐9 H ‐fluorene‐2,7‐diyl)bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane), followed by hydrolysis and quaternization.…”

Biotinylated Water-Soluble Conjugated Polymers：Synthesis and the Application in Biological Analysis

“…相比 而言, 生物功能化的水溶性共轭聚合物, 则可以通过受 体-配体之间的特异性反应来提高生物分子检测的选择 性和成像分析的靶向性. 目前, 已报道的水溶性共轭聚 合物的功能化基团主要为糖基 [15] 、 羧基 [16,17] 和氨基 [18,19] , 侧链修饰生物素 [20] 、氨基酸 [21] 、肽段 [22] 、核酸 [23] 或抗 体 [24] 等生物分子的功能化共轭聚合物还比较少 [25] . Figure 3 Responses of UV-visible absorbance (A) and fluorescence emission (B) to the concentration of PFPNBr-biotin 时, SA 的加入会使聚合物的荧光显著猝灭, 而对照蛋白 图 5 (A) pH 分别为 5, 7, 9 的体系中对蛋白的检测、(B) pH 为 7 时 NaCl 浓度对 SA 蛋白检测的影响和(C) pH 为 9 时 NaCl 浓度对 SA 蛋 白检测的影响 Figure 5 Detection of proteins with PFPNBr-biotin in solutions with pHs 5, 7 and 9 (A), influence of NaCl concentration on protein detection in solution of pH 7 (B) and pH 9 (C) BSA 对其荧光几乎没有影响, 因此在两种条件下都能 很好的识别靶蛋白.…”