Glycol Linker Research Articles

Synthesis and intensive analysis of antibody labeled single core magnetic nanoparticles for targeted delivery to the cell membrane

This work is dedicated to the synthesis and characterization of antibody labeled magnetic nanoparticles as promising tool for biomedical applications. Single core magnetic nanoparticles were synthesized by thermal decomposition technique, followed by surface modification with ligand based on polyethylene glycol derivative. Fluorochrome-labeled species-specific antibodies were covalently conjugated to MNPs through a polyethylene glycol linker. The immunofluorescent analysis showed the successful binding of anti-α-tubulin or anti-β-catenin antibodies conjugated MNPs to α-tubulin and β-catenin in 4T1 cells of mouse breast cancer.

Two for the Price of One: Heterobivalent Ligand Design Targeting Two Binding Sites on Voltage-Gated Sodium Channels Slows Ligand Dissociation and Enhances Potency.

Voltage-gated sodium (NaV) channels are pore-forming transmembrane proteins that play essential roles in excitable cells, and they are key targets for antiepileptic, antiarrhythmic, and analgesic drugs. We implemented a heterobivalent design strategy to modulate the potency, selectivity, and binding kinetics of NaV channel ligands. We conjugated μ-conotoxin KIIIA, which occludes the pore of the NaV channels, to an analogue of huwentoxin-IV, a spider-venom peptide that allosterically modulates channel gating. Bioorthogonal hydrazide and copper-assisted azide–alkyne cycloaddition conjugation chemistries were employed to generate heterobivalent ligands using polyethylene glycol linkers spanning 40–120 Å. The ligand with an 80 Å linker had the most pronounced bivalent effects, with a significantly slower dissociation rate and 4–24-fold higher potency compared to those of the monovalent peptides for the human NaV1.4 channel. This study highlights the power of heterobivalent ligand design and expands the repertoire of pharmacological probes for exploring the function of NaV channels.

Enhanced cytotoxicity of highly water-soluble gold nanoparticle-cyclopeptide conjugates in cancer cells

Conjugation of cytostatic drugs to nanomaterials seeks to improve their low bioavailability and selectivity to overcome the important associated side effects. In this work, we aimed to synthesize water-soluble gold nanoparticles as transporters for synthetic cyclic peptides with a potential anticancer activity but with a limited bioavailability. The highly water-soluble nanoparticles (2.5 nm diameter gold core) are coated with a mixture of polyethylene glycol linkers, one bearing a terminal hydroxyl group for increasing dispersibility in water, and the second bearing a carboxylic acid group for peptide conjugation through amide bond formation. Peptide-functionalized particles have a 9.7 ± 1.8 nm hydrodynamic diameter and are highly water-soluble and stable in solution for at least one year. The morphology of the gold cores as well as their organic coating was studied using Transmission Electron Microscopy, showing that the attachment of a limited number of peptides per nanoparticle leads to a uneven organic coating of two different thicknesses, one of 2.0 ± 0.6 nm formed by polyethylene glycol linkers, and a second of 3.6 ± 0.5 nm which includes the peptide. GNP significantly enhance the internalization of the cyclic peptide BPC734 in cells as compared to peptide in solution, with improved uptake in cancerous HT29 cells. Cytotoxicity studies show that peptide BPC734 in solution is toxic in the micromolar range, whereas peptide-functionalized particles are toxic at nanomolar peptide concentrations and with a significantly higher toxicity for cancerous cells. All these results, besides the stability and expected passive tumor targeting, make these particles a promising option for improving the bioavailability, efficacy, and selectivity in cancer therapy.

Eflapegrastim's enhancement of efficacy compared with pegfilgrastim in neutropenic rats supports potential for same-day dosing

Eflapegrastim (Rolontis) is a long-acting granulocyte colony-stimulating factor (G-CSF) with an IgG4 Fc fragment and short polyethylene glycol linker. Current G-CSF products are administered 24 hours after chemotherapy. The present study compares the duration of neutropenia (DN) with eflapegrastim or pegfilgrastim at 0, 2, 5, or 24 hours post chemotherapy. Eflapegrastim was evaluated by G-CSF receptor binding and bone marrow cell proliferation assays in vitro. Eflapegrastim-Fc component binding to Fcγ receptors C1q and FcRn was assessed by enzyme-linked immunosorbent assay. Neutropenia was induced in rats via intraperitoneal cyclophosphamide or docetaxel/cyclophosphamide. Rats received chemotherapy followed by vehicle, pegfilgrastim, or eflapegrastim at 2, 5, or 24 hours. The difference in DN after treatment was assessed. In vitro binding to G-CSF receptor of both agents was similar. Binding to FcRn and no binding to Fcγ receptors or C1q were observed with eflapegrastim. Studies in chemotherapy-induced neutropenic rats revealed shorter DN with eflapegrastim versus pegfilgrastim. Increased levels of G-CSF in serum and marrow were observed in groups treated with eflapegrastim versus those treated with pegfilgrastim. Although eflapegrastim and pegfilgrastim have similar in vitro binding affinity, the Fc fragment in eflapegrastim increases the uptake into bone marrow, resulting in increased therapeutic potential for chemotherapy-induced neutropenia. Eflapegrastim's greater marrow resident time provided a pharmacodynamic advantage over pegfilgrastim, translating into shortened duration of neutropenia. Our findings support eflapegrastim same-day administration with chemotherapy, warranting further evaluation in patients undergoing myelosuppressive chemotherapy.

Long-Range Ordered Water Correlations between A–T/C–G Nucleotides

Summary The interactions between complementary base pairs are crucial to the helical duplex structure of DNA. Although base-base interactions have been widely reported, the study of long-range interactions in the base-pairing processes is still a major challenge in this field. Here, we first study the long-range interactions between the base pairs by atomic force microscopy-based single-molecule force spectroscopy (SMFS). The SMFS results of A–T/C–G imply that there are weak long-range interactions between them, which have a range of 15–25 nm. Raman spectroscopy results imply that these weak interactions can be attributed to multiplex hydrogen bond interaction of ordered water structure between A–T/C–G nucleotides. In addition, the theoretical calculations deduce that the ideal structure of these water molecules exhibits a specific helical structure. Our findings might open up a new understanding of biological assembly processes and provide helpful strategies for bio-nanotechnology.

Self-Delivery Photodynamic Nanoinhibitors for Tumor Targeted Therapy and Metastasis Inhibition.

Simultaneous inhibitions of primary tumor growth and distant metastasis are very critical for cancer patients to improve their survival and cure rates. Although photodynamic therapy (PDT) shows great potential for primary tumor treatment, it often exacerbates hypoxia with a reduced therapeutic efficacy and subsequently contributes to carcinoma progression and metastatic dissemination. To solve these issues, self-delivery photodynamic nanoinhibitors (PNI) are developed for tumor targeted therapy and metastasis inhibition. PNI are composed of a carbonic anhydrase inhibitor (CAi), a hydrophilic poly(ethylene glycol) (PEG) linker, and a hydrophobic photosensitizer protoporphyrin IX (PpIX). Such self-delivery design of PNI avoids the premature release and heterogeneous distribution of CAi and PpIX to enhance the availability and synergism. Briefly, the CAi-based nanoinhibitors improve the selectivity of CAi for specific recognition and inhibition of tumor-associated isoform carbonic anhydrase (CA) IX, which would not only facilitate the targeted drug delivery of PNI but also regulate the hypoxia-induced signaling cascade and PDT resistance. Benefiting from the CA IX inhibition and targeted PDT, PNI exhibit a robust inhibitory effect on primary tumor growth and distant metastasis. This targeted self-delivery strategy sheds light on the photosensitizer-based molecular design to overcome the defect of traditional PDT.

Abstract LB-227: Preclinical development and characterization of STI-6129, an anti-CD38 antibody-drug conjugate, as a new therapeutic agent for multiple myeloma

Abstract CD38 is a validated target for the treatment of CD38-overexpressing hematologic malignancies such as multiple myeloma (MM). Daratumumab is the first anti-CD38 mAb drug approved by the FDA for use as single agent and in combination with standard therapies for MM. However, resistance to Daratumumab in both primary and refractory MM patients has been reported. Here we report the preclinical development of STI-6129 (also CD38-077), a CD38-targeting antibody-drug conjugate (ADC), as a new therapeutic agent for MM. STI-6129 consists of a fully human anti-CD38 antibody, STI-5171, identified from the Sorrento G-MAB® antibody library, conjugated to the microtubule inhibitor duostatin-5.2 (Duo-5.2) via a non-polyethylene glycol linker using our site-specific conjugation proprietary C-LOCK technology. STI-5171 binds specifically to CD38-positive but not CD38-negative tumor cell lines with a KD ~ 1.72E-8 M. STI-6129 is internalized into CD38-positive cells at a rate comparable to that of the unconjugated antibody STI-5171. In cytotoxicity studies, STI-6129 exhibited CD38-dependent cytotoxic activity against a panel of CD38-expressing tumor cell lines with the range of EC50 from 5-100 µg/mL. Importantly, STI-6129 does not display cytotoxic activity (EC50 > 150 μg/mL) against normal human PBMCs after 120 hr exposure. Mechanistic evaluation of STI-5171 compared to Daratumumab revealed that this antibody does not induce homotypic aggregation of tumor cells, a cell adhesion response that has been reported to be linked to drug resistance and increased metastatic potential. Further, the anti-tumor activity of STI-6129 showed broad, potent, and CD38-dependent in vivo efficacy in multiple xenograft animal models. Pharmacokinetic evaluation of STI-6129 in Daudi-Fluc tumor-bearing mice revealed that the ADC is stable with half-life (T1/2) of 7-11 days, comparable to that of the unconjugated antibody. The serum concentration of STI-6129 remained above the therapeutically effective level up to 1 week in mice after a single injection at 10 mg/kg. In cynomolgus monkey, the PK profiles of STI-6129 and STI-5171 were nearly identical, further confirming the stability of the ADC in monkey blood circulation.In summary, STI-6129 exhibits potent in vitro and in vivo anti-tumor activities in multiple CD38-positive hematological models. These results warrant further development of STI-6129, potentially as a better or alternative agent for treatment of multiple myeloma. Citation Format: Lingna Li, Andrew Hau, Wenyong Tong, Megan Lau, Tong Zhu, Katherine Fells, Angel Wei, Xiaoqing Li, Dylan Deng, Yingqing Sun, Ernest Kovacs, Alisher Khasanov, Zheng Yan, Panyun Zhu, Heyue Zhou, Henry Ji, Hui Li, Hong Zhang. Preclinical development and characterization of STI-6129, an anti-CD38 antibody-drug conjugate, as a new therapeutic agent for multiple myeloma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-227.

Abstract 2044: Chemotherapy induced neutropenia in rats following administration of eflapegrastim or pegfilgrastim on the same day at three different timepoints and at 24 hours post-chemotherapy

Abstract Background: Eflapegrastim is a long-acting G-CSF that is comprised of a G-CSF analog and a recombinant IgG4 Fc fragment conjugated at their N-termini via a short polyethylene glycol linker. Currently, G-CSF products are administered 24 hours after chemotherapy. We compared the duration of neutropenia (DN) after treatment with eflapegrastim and pegfilgrastim given on the same-day, at three different timepoints, and after 24 hours in chemotherapy-induced neutropenic rats. Method: Neutropenia was induced in rats via intraperitoneal administration of cyclophosphamide and docetaxel (TC) chemotherapy. Rats (5 animals per group) were assigned to dose groups of either vehicle or equivalent doses (based on human clinical doses) of pegfilgrastim (103.3 µg/kg) or eflapegrastim (61.8 µg/kg as G-CSF) on the same day as chemotherapy at 0, 2, and 5 hours or 24 hours after chemotherapy. The primary endpoint was the difference in DN after TC treatment and administration of eflapegrastim or pegfilgrastim at the specified timepoints. Results: In the vehicle group, the TC regimen induced neutropenia in all animals with an ANC nadir occurring on approximately Day 4 and a mean DN of nearly 7 days. The mean DN values for treatment with eflapegrastim on the same day, at 0, 2, and 5 hours, and after 24 hours were similar and the mean DN values for eflapegrastim were significantly lower than for pegfilgrastim at all dosing timepoints (Table). Time after Chemotherapy(hours)Mean Duration of Neutropenia (days)Difference (95% CI)Eflapegrastim Time vs 24 hoursDifference (95% CI)EflapegrastimPegfilgrastim00.62.2-1.6 (-3.067, -0.133)0.4 (-0.08, 1.28)20.21.8-1.6 (-2.84, -0.36)0 (-0.19, 0.59)50.01.2-1.2 (-1.20, -1.20)-0.2 (0, 0)240.21.8-1.6 (-2.84, -0.36)NA Conclusions: The DN for same-day treatment with eflapegrastim at 0, 2, and 5 hours was similar to that of the treatment after 24-hours. However, the mean DN values were significantly lower for eflapegrastim than pegfilgrastim at all time points. Further exploration of the potential advantage of same-day dosing with eflapegrastim in patients undergoing chemotherapy is warranted. Citation Format: Yu-Yon Kim, Eunjung Kim, Hyesun Han, Seungjae Baek, Shanta Chawla, Prasad Kolli, Gajanan Bhat, Francois Lebel. Chemotherapy induced neutropenia in rats following administration of eflapegrastim or pegfilgrastim on the same day at three different timepoints and at 24 hours post-chemotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2044.

Graft Architecture Guided Simultaneous Control of Degradation and Mechanical Properties of In Situ Forming and Fast Dissolving Polyaspartamide Hydrogels.

Polyaspartamide, derived from polysuccinimide (PSI), has the advantage of conveniently presenting desired functional groups by ring-opening addition of amine-based nucleophiles to the succinimidyl ring moieties of PSI. Using diamines with varying lengths of poly(ethylene glycol) linker, polyaspartamide presenting amine groups with controllable grafting density and length, namely, poly(2-hydroxyethyl aspartamide)-g-amino-poly(ethylene glycol) (PHEA-PEGAm) could be synthesized. This PHEA-PEGAm was then used to develop in situ forming hydrogels by Schiff base formation with aldehyde-containing alginate (Alg-ALD). By modulating the graft architecture (i.e., grafting length and density), the mechanical properties of the resulting Alg-PHEA hydrogels could be controlled in a broad range. Remarkably, the hydrogels were shown to undergo facile degradation and complete dissolution in physiological conditions, regardless of hydrogel mechanics, by the expedited hydrolysis through the action of remaining amine groups, which was also heavily influenced by the graft architecture. Moreover, the rate of degradation could be further controlled by additional ionic cross-linking of alginate. The potential application as an injectable drug delivery system was demonstrated by measuring drug release kinetics and monitoring degradation ex vivo.

Pegylated Deoxycholic Acid Coated Gold Nanoparticles as a Highly Stable CT Contrast Agent

AbstractThe present study has been dedicated to the synthesis of a new and highly stable computed tomography contrast agent based on pegylated deoxycholic acid‐ coated gold nanoparticles (DCA‐PEG‐GNPs) measuring 17 nm in size. To stabilize the gold nanoparticles (GNPs) as well as increasing their vascular retention time, polyethylene glycol, PEG, with a molecular weight of 4 KD, was applied. Besides, for target delivery, deoxycholic acid (DCA) as a biologically active compound and a secondary bile acid, capable of interfering with some cancers, were selected. The bile acid was attached to the nanoparticle's surface with a polyethylene glycol (MW=1 KD) linker via an etherification reaction. Finally, the activity of the prepared compound was studied by means of a clinical CT instrument at various KVp values. The gained results depicted a very high activity of the compound to attenuate X‐rays along with making contrast enhancement, even better than those of Visipaque as a commercial contrast agent. In addition, the DCA‐PEG‐GNPs displayed remarkable stability in a wide range of pHs,i. e. 2.5‐11, and in different temperature conditions, ranging between −78 °C to 48 °C.

Dually Reactive Long Recombinant Linkers for Bioconjugations as an Alternative to PEG.

Covalent cross-linking of biomolecules can be useful in pursuit of tissue targeting or dual targeting of two receptors on cell surfaces for avidity effects. Long linkers (>10 kDa) can be advantageous for such purposes, and poly(ethylene glycol) (PEG) linkers are most commonly used due to the high aqueous solubility of PEG and its relative inertness toward biological targets. However, PEG is non-biodegradable, and available PEG linkers longer than 5 kDa are heterogeneous (polydisperse), which means that conjugates based on such materials will be mixtures. We describe here recombinant linkers of distinct lengths, which can be expressed in yeast, which are polar, and which carry orthogonal reactivity at each end of the linker, thus allowing chemoselective cross-linking of proteins. A conjugate between insulin and either of the two trypsin inhibitor peptides/proteins exemplifies the technology, using a GQAP-based linker of molecular weight of 17 848, having one amine at the N-terminal, and one Cys, at the C-terminal. Notably, yeast-based expression systems typically give products with mixed disulfides when expressing proteins that are equipped with one unpaired Cys, namely, mixed disulfides with glutathione, free Cys amino acid, and/or a protein homodimer. To obtain a homogeneous linker, we worked out conditions for transforming the linker with mixed disulfides into a linker with a homogeneous disulfide, using excess 4-mercaptophenylacetic acid. Subsequently, the N-terminal amine of the linker was transformed into an azide, and the C-terminal Cys disulfide was reduced to a free thiol and reacted with halo-acetyl insulin. The N-terminal azide was finally conjugated to either of the two types of alkyne-containing trypsin inhibitor peptides/proteins. This reaction sequence allowed the cross-linked proteins to carry internal disulfides, as no reduction step was needed after protein conjugations. The insulin–trypsin inhibitor conjugates were shown to be stabilized toward enzymatic digestions and to have partially retained binding to the insulin receptor.

One-Pot Synthesis of a Linear [4]Catenate Using Orthogonal Metal Templation and Ring-Closing Metathesis.

The efficient synthesis of well-defined, linear oligocatenanes possessing multiple mechanical bonds remains a formidable challenge in the field of mechanically interlocked molecules. Here, a one-pot synthetic strategy is described to prepare a linear [4]catenate using orthogonal metal templation between a macrocycle precursor, composed of terpyridine and phenanthroline ligands spaced by flexible glycol linkers, and a closed phenanthroline-based molecular ring. Implementation of two simultaneous ring-closing metathesis reactions after metal complexation resulted in the formation of three mechanical bonds. The linear [4]catenate product was isolated in 55% yield as a mixture of topological diastereomers. The intermediate metal complexes and corresponding interlocked products (with and without metals) were characterized by nuclear magnetic resonance, mass spectrometry, gel permeation chromatography, and UV-vis absorption spectroscopy. We envision that this general synthetic strategy may pave the way for the synthesis of higher order linear oligocatenates/catenanes with precise molecular weights and four or more interlocking molecular rings.

Allosterically Linked Binding Sites in Serotonin Transporter Revealed by Single Molecule Force Spectroscopy.

Crystal structures and experiments relying on the tools of molecular pharmacology reported conflicting results on ligand binding sites in neurotransmitter/sodium symporters (NSS). We explored the number and functionality of ligand binding sites of NSS in a physiological setting by designing novel tools for atomic force microscopy (AFM). These allow for directly measuring the interaction forces between the serotonin transporter (SERT) and the antidepressant S-citalopram (S-CIT) on the single molecule level: the AFM cantilever tips were functionalized with S-CIT via a flexible polyethylene glycol (PEG) linker. The tip chemistry was validated by specific force measurements and recognition imaging on CHO cells. Two distinct populations of characteristic binding strengths of S-CIT binding to SERT were revealed in Na+-containing buffer. In contrast, in Li+-containing buffer, SERT showed only low force interactions. Conversely, the vestibular mutant SERT-G402H merely displayed the high force population. These observations provide physical evidence for the existence of two binding sites in SERT. The dissociation rate constant of both binding sites was extracted by varying the dynamics of the force-probing experiments. Competition experiments revealed that the two sites are allosterically coupled and exert reciprocal modulation.

In Situ Magnetic Control of Macroscale Nanoligand Density Regulates the Adhesion and Differentiation of Stem Cells.

Developing materials with remote controllability of macroscale ligand presentation can mimic extracellular matrix (ECM) remodeling to regulate cellular adhesion in vivo. Herein, we designed charged mobile nanoligands with superparamagnetic nanomaterials amine-functionalized and conjugated with polyethylene glycol linker and negatively charged RGD ligand. We coupled negatively a charged nanoligand to a positively charged substrate by optimizing electrostatic interactions to allow reversible planar movement. We demonstrate the imaging of both macroscale and in situ nanoscale nanoligand movement by magnetically attracting charged nanoligand to manipulate macroscale ligand density. We show that in situ magnetic control of attracting charged nanoligand facilitates stem cell adhesion, both in vitro and in vivo, with reversible control. Furthermore, we unravel that in situ magnetic attraction of charged nanoligand stimulates mechanosensing-mediated differentiation of stem cells. This remote controllability of ECM-mimicking reversible ligand variations is promising for regulating diverse reparative cellular processes in vivo.

Versatile Bioconjugation Strategies of PEG-Modified Upconversion Nanoparticles for Bioanalytical Applications.

Lanthanide-doped upconversion nanoparticles (UCNPs) display highly beneficial photophysical features for background-free bioimaging and bioanalysis; however, they are instable in high ionic strength buffers, have no functional groups, and are nonspecifically interacting. Here, we have prepared NIR-excitable UCNPs that are long-term colloidally stable in buffered media and possess functional groups. Heterobifunctional poly(ethylene glycol) (PEG) linkers bearing neridronate and alkyne or maleimide were attached to UCNPs via a ligand exchange. Streptavidin (SA)-conjugates were prepared by click reaction of UCNP@PEG-alkyne and SA-azide. Antihuman serum albumin pAbF antibody was modified with azide groups and conjugated to UCNP@PEG-alkyne via click reaction; alternatively, the antibody, after mild reduction of its disulfide bonds, was conjugated to UCNP@PEG-maleimide. We employed these nanoconjugates as labels for an upconversion-linked immunosorbent assay. SA-based labels achieved the lowest LOD of 0.17 ng/mL for the target albumin, which was superior compared to a fluorescence immunoassay (LOD 0.59 ng/mL) or an enzyme-linked immunoassay (LOD 0.56 ng/mL).

Defining the Design Parameters for in Vivo Enzyme Delivery Through Protein Spherical Nucleic Acids.

The translation of proteins as effective intracellular drug candidates is limited by the challenge of cellular entry and their vulnerability to degradation. To advance their therapeutic potential, cell-impermeable proteins can be readily transformed into protein spherical nucleic acids (ProSNAs) by densely functionalizing their surfaces with DNA, yielding structures that are efficiently taken up by cells. Because small structural changes in the chemical makeup of a conjugated ligand can affect the bioactivity of the associated protein, structure–activity relationships of the linker bridging the DNA and the protein surface and the DNA sequence itself are investigated on the ProSNA system. In terms of attachment chemistry, DNA-based linkers promote a sevenfold increase in cellular uptake while maintaining enzymatic activity in vitro as opposed to hexaethylene glycol (HEG, Spacer18) linkers. Additionally, the employment of G-quadruplex-forming sequences increases cellular uptake in vitro up to fourfold. When translating to murine models, the ProSNA with a DNA-only shell exhibits increased blood circulation times and higher accumulation in major organs, including lung, kidney, and spleen, regardless of sequence. Importantly, ProSNAs with an all-oligonucleotide shell retain their enzymatic activity in tissue, whereas the native protein loses all function. Taken together, these results highlight the value of structural design in guiding ProSNA biological fate and activity and represent a significant step forward in the development of intracellular protein-based therapeutics.

Polydopamine‐mediated polypyrrole/doxorubicin nanocomplex for chemotherapy‐enhanced photothermal therapy in both NIR‐I and NIR‐II biowindows against tumor cells

AbstractPhotothermal therapy (PTT) is featured by the desirable spatiotemporal controllability and excellent specificity, which has been identified as one of the important tumor treatment methods. Although promising, the efficacy of PTT is still limited and needs further improvement. In this work, a kind of PPy‐PDA‐PEG@DOX nanocomplex was designed and constructed for chemotherapy‐enhanced PTT in both near‐infrared (NIR)‐I and NIR‐II biowindows against tumor cells, which was integrated by the polypyrrole (PPy) core, polydopamine (PDA) shell, polyethylene glycol (PEG) linkage, and doxorubicin (DOX) payload. This constructed PPy‐PDA‐PEG@DOX nanocomplex was uniform in size around 56.3 nm, and with the optimized DOX loading content at 37.4%. The photothermal conversion efficiencies of this nanocomplex were calculated to be around 23.1 and 30.8% in NIR‐I and NIR‐II biowindows, respectively, showing good photothermal capacity and stability. The loaded DOX could be released in stimuli‐responsive manners. The therapeutic efficacy was enhanced by PPy‐PDA‐PEG@DOX nanocomplex, indicating the high effectiveness of chemotherapy‐enhanced phototherapy. This developed PPy‐PDA‐PEG@DOX nanocomplex shows promising applications in tumor treatment applications.

A Novel Bivalent Mannosylated Targeting Ligand Displayed on Nanoparticles Selectively Targets Anti-Inflammatory M2 Macrophages.

Persistent activation of macrophages (MP)s into a proinflammatory M1 or anti-inflammatory M2 phenotype plays a role in several pathological conditions, including autoimmune diseases, fibrosis, infections, atherosclerosis and tumor development. The mannose receptor (MR, CD206), expressed at low levels on resting MPs and absent on M1 MPs, is highly expressed on M2 MPs, making it a potential target and drug delivery portal. Recently, we developed a novel, highly selective MR targeting ligand (MRTL), consisting of two mannose molecules separated by a monodisperse 12 unit poly(ethylene glycol) linker, to enhance the cellular uptake of polymeric nanocarriers. The feasibility of using the MRTL ligand for selectively targeting M2 MPs for intracellular delivery of nanoparticles (NPs) was investigated. Rat peritoneal MPs were differentiated into an M1 or M2 phenotype using IFN-γ and IL-4/IL-13, respectively. Expression of the M1 marker, inducible nitric oxide synthase (iNOS), and the M2 markers arginase (Arg)-1 and MR (at both the mRNA and protein levels) confirmed MP phenotypic activation. Resting, M1 and M2 MPs were treated with fluorescein isothiocyanate (FITC)-labeled MRTL or NPs displaying FITC-labeled MRTL at two surface densities (1 and 10%) and examined by confocal microscopy. Intracellular fluorescence was also quantified. Uptake of the MRTL was 2.4- and 11.8-fold higher in M2 MPs when compared to resting or M1 MPs, respectively, consistent with marker expression levels. Mannan, a competitive inhibitor of the MR, abrogated MRTL uptake. MRTL also co-localized with a fluid-phase endocytosis marker, further suggesting that uptake was mediated by MR-mediated endocytosis. Intracellular NP fluorescence was confirmed by flow cytometry and by confocal microscopy. MRTL-NPs accumulated intracellularly with no significant cell surface binding, suggesting efficient translocation. NPs displaying a low surface density (1%) of the MRTL exhibited significantly higher (2.3-fold) uptake into M2 MPs, relative to resting and M1 MPs. The 10% MRTL-NPs displayed greater uptake by M2 MPs when compared to resting and M1 MPs, but less uptake than 1% MRTL-NPs into M2 MPs. Control FITC-labeled plain NPs did not exhibit selective MP uptake. These studies demonstrate that M2 MPs are selectively targeted by NPs displaying a novel bivalent ligand that utilizes the MR as a target/portal for cell entry. This study also establishes the feasibility of the approach allowing for further investigation in vivo.

Design and preclinical evaluation of nanostars for the passive pretargeting of tumor tissue

IntroductionPretargeting strategies that do not rely on the expression of molecular targets have expanded imaging and therapy options for cancer patients. Nanostars with designed multivalency and which highly accumulate in tumor tissue via the enhanced permeability and retention (EPR) effect may therefore be the ideal vectors for the development of a passive pretargeting approach. MethodsNanostars were synthesized, consisting of 7–8 center-cross-linked arms that were modified with trans-cyclooctene (TCO) using poly(ethylene glycol) (PEG) linkers of 12 or 106 monomer units or without linker. The bioorthogonal click reaction with radiofluorinated 2,2′-(7-(2-(tetrazine-poly(ethyleneglycol)11-amino)-2-oxoethyl)-1,4,7-triazonane-1,4-diyl)diacetic acid ([18F]F-Tz-PEG11-NODA) or 2,2′-(7-(2-(tetrazine-amino)-2-oxoethyl)-1,4,7-triazonane-1,4-diyl)diacetic acid ([18F]F-Tz-NODA) was measured by ex vivo biodistribution studies and positron emission tomography (PET) in mice bearing tumors with high EPR characteristics. Bioorthogonal masking was performed using a tetrazine-functionalized dextran polymer (Tz-DP). ResultsHighest tumor accumulation of [18F]F-Tz-PEG11-NODA was observed for nanostars functionalized with TCO without linker, with a tumor uptake of 3.2 ± 0.4%ID/g and a tumor-to-muscle ratio of 12.8 ± 4.2, tumor-to-large intestine ratio of 0.5 ± 0.3 and tumor-to-kidney ratio of 2.0 ± 0.3, being significantly higher than for nanostars functionalized with TCO-PEG12 (P < 0.05) or TCO-PEG106 (P < 0.05). Tumor uptake and tumor-to-tissue ratios did not improve upon bioorthogonal masking with Tz-DP or when using a smaller, more lipophilic tetrazine([18F]F-Tz-NODA). ConclusionsA pretargeting strategy was developed based on the passive delivery of TCO-functionalized nanostars. Such a strategy would allow for the imaging and treatment of tumors with apparent EPR characteristics, with high radioactive tumor doses and minimal doses to off-target tissues.

Enhancement of label-free biosensing of cardiac troponin I.

The detection of cardiac troponin I (cTnI) is clinically used to monitor myocardial infarctions (MI) and other heart diseases. The development of highly sensitive detection assays for cTnI is needed for the efficient diagnosis and monitoring of cTnI levels. Traditionally, enzyme-based immunoassays have been used for the detection of cTnI. However, the use of label-free sensing techniques have the advantage of potentially higher speed and lower cost for the assays. We previously reported a Photonic Crystal-Total Internal Reflection (PC-TIR) biosensor for label-free quantification of cTnI. To further improve on this, we present a comparative study between an antibody based PC-TIR sensor that relies on recombinant protein G (RPG) for the proper orientation of anti-cTnI antibodies, and an aptamer-based PC-TIR sensor for improved sensitivity and performance. Both assays relied on the use of polyethylene glycol (PEG) linkers to facilitate the modification of the sensor surfaces with biorecognition elements and to provide fluidity of the sensing surface. The aptamer-based PC-TIR sensor was successfully able to detect 0.1 ng/mL of cTnI. For the antibody-based PC-TIR sensor, the combination of the fluidity of the PEG and the increased number of active antibodies allowed for an improvement in assay sensitivity with a low detection limit of 0.01 ng/mL. The developed assays showed good performance and potential to be applied for the detection of cTnI levels in clinical samples upon further development.