Selectively Positioned Catechol Moiety Supports Ultrashort Self-Assembling Peptide Hydrogel Adhesion for Coral Restoration.

Coral reef survival is threatened globally. One way to restore this delicate ecosystem is to enhance coral growth by the controlled propagation of coral fragments. To be sustainable, this technique requires the use of biocompatible underwater adhesives. Hydrogels based on rationally designed ultrashort self-assembling peptides (USP) are of great interest for various biological and environmental applications, due to their biocompatibility and tunable mechanical properties. Implementing superior adhesion properties to the USP hydrogel compounds is crucial in both water and high ionic strength solutions and is relevant in medical and marine environmental applications such as coral regeneration. Some marine animals secrete large quantities of the aminoacids dopa and lysine to enhance their adhesion to wet surfaces. Therefore, the addition of catechol moieties to the USP sequence containing lysine (IIZK) should improve the adhesive properties of USP hydrogels. However, it is challenging to place the catechol moiety (Do) within the USP sequence at an optimal position without compromising the hydrogel self-assembly process and mechanical properties. Here, we demonstrate that, among three USP hydrogels, DoIIZK is the least adhesive and that the adhesiveness of the IIZDoK hydrogel is compromised by its poor mechanical properties. The best adhesion outcome was achieved using the IIZKDo hydrogel, the only one to show equally sound adhesive and mechanical properties. A mechanistic understanding of this outcome is presented here. This property was confirmed by the successful gluing of coral fragments by means of IIZKDo hydrogel that are still thriving after more than three years since the deployment. The validated biocompatibility of this underwater hydrogel glue suggests that it could be advantageously implemented for other applications, such as surgical interventions.

Ternary Synergy of Lys, Dopa, and Phe Results in Strong Cohesion of Peptide Films.

Synergistic interactions between 3,4-dihydroxyphenylalanine (Dopa, Y*), cationic residues, and the aromatic rings have been recently highlighted as influential factors that enhance the underwater adhesion strength of mussel foot proteins and their derivatives. In this study, we report the first ever evidence of a cation-catechol-benzene ternary synergy between Y*, lysine (Lys, K), and phenylalanine (Phe, F) in adhesive peptides. We synthesized three hexapeptides containing a different combination of Y*, K, and F, i.e., (KY*)3, (KF)3, and (KY*F)2, respectively, exploring the relationship between the cohesive performance and molecular architecture of peptides. The peptide with the (KY*F)2 sequence displays the strongest underwater cohesion energy of 10.3 ± 0.3 mJ m-2 from direct nanoscale surface force measurements. Combined with molecular dynamics simulation, we demonstrated that there are more bonding interactions (including cation-π, π-π, and hydrogen bond interactions) in (KY*F)2 compared to the other two peptides. In addition, peptide (KY*F)2 still shows the strongest cohesive energies of 7.6 ± 0.7 and 3.7 ± 0.5 mJ m-2 in acidic and high-ionic strength environments, respectively, although the cohesive energy decreases compared to the value in pure water. Our results further explain the underwater cohesion mechanisms combining multiple interactions and offer insights on designing Dopa containing underwater adhesives.

Effect of Cross-Linkers on Mussel- and Elastin-Inspired Adhesives on Physiological Substrates.

Surgical adhesives can be useful in wound closure because they reduce the risk of infection and pain associated with sutures and staples. However, there are no commercially available surgical adhesives for soft tissue wound closure. To be effective, soft tissue adhesives must be soft and flexible, strongly cohesive and adhesive, biocompatible, and effective in a moist environment. To address these criteria, we draw inspiration from the elasticity and resilience of elastin proteins and the adhesive of marine mussels. We used an elastin-like polypeptide (ELP) for the backbone of our adhesive material due to its elasticity and biocompatibility. A mussel-inspired adhesive molecule, l-3,4-dihydroxyphenylalanine (DOPA), was incorporated into the adhesive to confer wet-setting adhesion. In this study, an ELP named YKV was designed to include tyrosine residues and lysine residues, which contain amine groups. A modified version of YKV, named mYKV, was created through enzymatic conversion of tyrosine residues into DOPA. The ELPs were combined with iron(III) nitrate, sodium periodate, and/or tris(hydroxymethyl)phosphine (THP) cross-linkers to investigate the effect of DOPA- and amine-based cross-linking on adhesion strength and cure time on porcine skin in a warm, humid environment. Incorporation of DOPA into the ELP increased adhesive strength by 2.5 times and reduced failure rates. Iron cross-linkers improved adhesion in the presence of DOPA. THP increased adhesion for all proteins tested even in the absence of DOPA. Using multiple cross-linkers in a single formulation did not significantly improve adhesion. The adhesives with the highest performance (iron nitrate mixed with mYKV and THP mixed with YKV or mYKV) on porcine skin had 10-18 times higher adhesion than a commercial sealant and reached appreciable adhesive strength within 10 min.

Direct dynamic read-out of molecular chirality with autonomous enzyme-driven swimmers.

A key approach for designing bioinspired machines is to transfer concepts from nature to man-made structures by integrating biomolecules into artificial mechanical systems. This strategy allows the conversion of molecular information into macroscopic action. Here, we describe the design and dynamic behaviour of hybrid bioelectrochemical swimmers that move spontaneously at the air-water interface. Their motion is governed by the diastereomeric interactions between immobilized enantiopure oligomers and the enantiomers of a chiral probe molecule present in solution. These dynamic bipolar systems are able to convert chiral information present at the molecular level into enantiospecific macroscopic trajectories. Depending on the enantiomer in solution, the swimmers will move clockwise or anticlockwise; the concept can also be used for the direct visualization of the degree of enantiomeric excess by analysing the curvature of the trajectories. Deciphering in such a straightforward way the enantiomeric ratio could be useful for biomedical applications, for the read-out of food quality or as a more general analogue of polarimetric measurements.

Antiviral Activity of Peptide-Based Assemblies.

The COVID-19 pandemic highlighted the importance of developing surfaces and coatings with antiviral activity. Here, we present, for the first time, peptide-based assemblies that can kill viruses. The minimal inhibitory concentration (MIC) of the assemblies is in the range tens of micrograms per milliliter. This value is 2 orders of magnitude smaller than the MIC of metal nanoparticles. When applied on a surface, by drop casting, the peptide spherical assemblies adhere to the surface and form an antiviral coating against both RNA- and DNA-based viruses including coronavirus. Our results show that the coating reduced the number of T4 bacteriophages (DNA-based virus) by 3 log, compared with an untreated surface and 6 log, when compared with a stock solution. Importantly, we showed that this coating completely inactivated canine coronavirus (RNA-based virus). This peptide-based coating can be useful wherever sterile surfaces are needed to reduce the risk of viral transmission.

Surface modification by poly(ethylene glycol) with different end-grafted groups: Experimental and theoretical study.

Dihydroxyphenylalanine (DOPA) is extensively reported to be a surface-independent anchor molecule in bioadhesive surface modification and antifouling biomaterial fabrication. However, the mechanisms of DOPA adsorption on versatile substrates and the comparison between experimental results and theoretical results are less addressed. We report the adsorption of DOPA anchored monomethoxy poly(ethylene glycol) (DOPA-mPEG) on substrates and surface wettability as well as antifouling property in comparison with thiol and hydroxyl anchored mPEG (mPEG-SH and mPEG-OH). Gold and hydroxylated silicon were used as model substrates to study the adsorptions of mPEGs. The experimental results showed that the DOPA-mPEG showed higher affinity to both gold and silicon wafers, and the DOPA-mPEG modified surfaces had higher resistance to protein adsorption than those of mPEG-SH and mPEG-OH. It is revealed that the surface wettability is primary for surface fouling, while polymer flexibility is the secondary parameter. We present ab initio calculations of the adsorption of mEGs with different end-functionalities on Au and hydroxylated silicon wafer (Si-OH), where the binding energies are obtained. It is established that monomethoxy ethylene glycol (mEG) with DOPA terminal DOPA-mEG is clearly favored for the adsorption with both gold and Si-OH surfaces due to the bidentate Au-O interactions and the bidentate O-H bond interactions, in agreement with experimental evidence.

A mussel-inspired film for adhesion to wet buccal tissue and efficient buccal drug delivery.

Administration of drugs via the buccal route has attracted much attention in recent years. However, developing systems with satisfactory adhesion under wet conditions and adequate drug bioavailability still remains a challenge. Here, we propose a mussel-inspired mucoadhesive film. Ex vivo models show that this film can achieve strong adhesion to wet buccal tissues (up to 38.72 ± 10.94 kPa). We also demonstrate that the adhesion mechanism of this film relies on both physical association and covalent bonding between the film and mucus. Additionally, the film with incorporated polydopamine nanoparticles shows superior advantages for transport across the mucosal barrier, with improved drug bioavailability (~3.5-fold greater than observed with oral delivery) and therapeutic efficacy in oral mucositis models (~6.0-fold improvement in wound closure at day 5 compared with that observed with no treatment). We anticipate that this platform might aid the development of tissue adhesives and inspire the design of nanoparticle-based buccal delivery systems.

Unravelling the nature of the α-keratin EPR signal: an ab initio study.

Fingernail as a biodosimetry material, analyzed by the EPR technique, has attracted great attention in several experimental studies. One of the most challenging issues that should be addressed is additional signals, masking the radiation-induced signals (RIS) in EPR dosimetry analyses. In this work, we conducted a theoretical study of the RIS radicals and mechanisms to propose robust methods to distinguish the original signal from the irradiated nails' unwanted noise. Also, the proposed approach includes procedures to improve the accuracy of the dosimetry measurements. In our research, three categories of cysteine, DOPA and cystine radicals were considered due to their dominant abundance during the α-keratin reduction-oxidation processes. The SOMO-HOMO inversion is observed while investigating the electronic structure in these quasi-closed-shell systems. Furthermore, we demonstrated that the SOMO-HOMO gap is proportional to the spin localization. Indeed, new peaks in the EPR signals are not observed when the amino acid sequences are different. Moreover, the studied structures' neighborhood effect merely leads to a small change in the peak broadening of the EPR signals. On-the-fly magnetic parameter calculations were used to evaluate the system dynamics' effect on the broadening of the EPR signals in a molecular dynamics simulation. Comparing the calculated parameters with computational and experimental results in other studies helps assign low dose peaks to the corresponding tyrosyl phenoxyl radical.

Inhibition of oral biofilm formation by zwitterionic nonfouling coating.

Inhibition of oral biofilm formation is critical to prevent and treat dental caries and periodontal diseases. In this study, we synthesized zwitterionic poly(carboxybetaine) (pCB) based polymer as a nonfouling coating to provide anti-bacterial properties to tooth surfaces. Four catechol derived l-3,4-dihydroxyphenylalanine (DOPA) groups were conjugated to pCB to serve as a surface anchoring group. The pCB-(DOPA)4 polymer was coated on the hydroxyapatite (HA) and enamel samples by simple immersion and characterized by Raman spectroscopy. The nonfouling effectiveness of the pCB based coating was determined by protein adsorption and bacterial adhesion assays. The coating was transparent on sample surfaces. The protein adsorption was significantly reduced to 8.2% and 6.9%, respectively, on pCB-(DOPA)4 coated HA and enamel samples. The pCB-(DOPA)4 -coated samples also demonstrated significantly fewer adhered Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus mutants compared to the control. This novel coating material provides an innovative approach to resist biofilm formation on tooth surfaces and has great potential in future dental clinical applications.

Density Functional Theory-Based Calculation Shed New Light on the Bizarre Addition of Cysteine Thiol to Dopaquinone.

Two types of melanin pigments, brown to black eumelanin and yellow to reddish brown pheomelanin, are biosynthesized through a branched reaction, which is associated with the key intermediate dopaquinone (DQ). In the presence of l-cysteine, DQ immediately binds to the -SH group, resulting in the formation of cysteinyldopa necessary for the pheomelanin production. l-Cysteine prefers to bond with aromatic carbons adjacent to the carbonyl groups, namely C5 and C2. Surprisingly, this Michael addition takes place at 1,6-position of the C5 (and to some extent at C2) rather than usually expected 1,4-position. Such an anomaly on the reactivity necessitates an atomic-scale understanding of the binding mechanism. Using density functional theory-based calculations, we investigated the binding of l-cysteine thiolate (Cys-S-) to DQ. Interestingly, the C2-S bonded intermediate was less energetically stable than the C6-S bonded case. Furthermore, the most preferred Cys-S--attacked intermediate is at the carbon-carbon bridge between the two carbonyls (C3-C4 bridge site) but not on the C5 site. This structure allows the Cys-S- to migrate onto the adjacent C5 or C2 with small activation energies. Further simulation demonstrated a possible conversion pathway of the C5-S (and C2-S) intermediate into 5-S-cysteinyldopa (and 2-S-cysteinyldopa), which is the experimentally identified major (and minor) product. Based on the results, we propose that the binding of Cys-S- to DQ proceeds via the following path: (i) coordination of Cys-S- to C3-C4 bridge, (ii) migration of Cys-S- to C5 (C2), (iii) proton rearrangement from cysteinyl -NH3+ to O4 (O3), and (iv) proton rearrangement from C5 (C2) to O3 (O4).

Surface bioengineering of diverse orthopaedic implants with optional functions via bioinspired molecular adhesion and bioorthogonal conjugations.

In this work, we reported an upgraded mussel-inspired strategy for surface bioengineering of osteoimplants by combination of mussel adhesion and bioorthogonal click chemistry. The main idea of this strategy is a mussel-inspired synthetic peptide containing multiple 3,4-dihydroxy-L-phenylalanine (DOPA) units and a dibenzocyclooctyne (DBCO) terminal (DOPA-DBCO). According to the mussel adhesion mechanism, the DOPA-DBCO peptide could stably adhere onto a variety of material surface, leaving the residual DBCO groups on the surface. Then, the DBCO residues could be employed for a second-step bioorthogonal conjugation with azide-capping biomolecules through bioorthogonal click chemistry, finally leading to the biomodified surfaces. To demonstrate the generality of our strategy for surface biomodification of diversified orthopaedic materials including metallic and polymeric substrates, we here conceptually conjugated some typical azide-capping biomolecules on both metal and polymeric surfaces. The results definitely verified the feasibility for engineering of functional surfaces with some essential requirements of osteoimplants, for example, the ability to facilitate cell adhesion, suppress bacterial infection, and promote osteogenesis. In a word, this study indicated that our novel surface strategy would show broad applicability for diverse osteoimplants and in different biological scenarios. We can also image that the molecular specificity of bioorthogonal conjugation and the universality of mussel adhesion mechanism may jointly provide a versatile surface bioengineering method for a wider range of biomedical implants.

Radiosynthesis challenges of 11C and 18F-labeled radiotracers in the FX2C/N tracerlab and their validation through PET-MR imaging.

Glucose is the renowned source of the energy for the cancer growth, that's the reason for [18F]FDG success and make it widely used radiotracer. Though [18F]FDG has its own inherent limitations therefore many tracers have been developed to target specific receptors, and other metabolic routes. We have used FX2C and FX2N Tracerlab modules for the synthesis of the [11C]methionine, [18F]choline and [18F]fluorodopa via nucleophilic pathway in FX2C/N module. [11C]methionine was standardized in FX2C module using two different precursors, and purified using C18 cartridge based technique. [18F]methylcholine was synthesized using dimethylaminoethanol precursor and purified using cartridge-based method. [18F]fluorodopa was synthesized using nucleophilic precursor and purified using in-built preparative HPLC on FX2N module. All radioactive intermediates and chemical impurities were evaluated by analytical HPLC. The radiochemical purity of D and L-[11C]methionine were 4.6 ± 3.2% and 95.4 ± 3.6% while other chemical impurities were less than prescribed limits with yield of 20 ± 5%. [18F]fluoromethylcholine was prepared with high radiochemical purity of 97.3 ± 2.6% with yield of 8 ± 3%. [18F]fluorodopa was synthesized with high radiochemical purity of 95.8 ± 1.4% with 15 ± 3% yield. The adaptation of [18F]fluorodopa synthesis to FX2N module via designing synthesis sequence and purified through on-line HPLC has provided high radiochemical purity. PET-MR imaging was done using these tracers which have validated the synthesis and their availability for future clinical applications.

Visual interpretation, not SUV ratios, is the ideal method to interpret 18F-DOPA PET scans to aid in the cure of patients with focal congenital hyperinsulinism.

INTRODUCTION: Congenital hyperinsulinism is characterized by abnormal regulation of insulin secretion from the pancreas causing profound hypoketotic hypoglycemia and is the leading cause of persistent hypoglycemia in infants and children. The main objective of this study is to highlight the different mechanisms to interpret the 18F-DOPA PET scans and how this can influence outcomes. MATERIALS AND METHODS: After 18F-Fluoro-L-DOPA was injected intravenously into 50 subjects' arm at a dose of 2.96-5.92 MBq/kg, three to four single-bed position PET scans were acquired at 20, 30, 40 and 50-minute post injection. The radiologist interpreted the scans for focal and diffuse hyperinsulinism using a visual interpretation method, as well as determining the Standard Uptake Value ratios with varying cut-offs. RESULTS: Visual interpretation had the combination of the best sensitivity and positive prediction values. CONCLUSIONS: In patients with focal disease, SUV ratios are not as accurate in identifying the focal lesion as visual inspection, and cases of focal disease may be missed by those relying on SUV ratios, thereby denying the patients a chance of cure. We recommend treating patients with diazoxide-resistant hyperinsulinism in centers with dedicated multidisciplinary team comprising of at least a pediatric endocrinologist with a special interest in hyperinsulinism, a radiologist experienced in interpretation of 18F-Fluoro-L-DOPA PET/CT scans, a histopathologist with experience in frozen section analysis of the pancreas and a pancreatic surgeon experienced in partial pancreatectomies in patients with hyperinsulinism.

Biomimetic double-sided polypropylene mesh modified by DOPA and ofloxacin loaded carboxyethyl chitosan/polyvinyl alcohol-polycaprolactone nanofibers for potential hernia repair applications.

Polypropylene (PP) meshes are the most widely used as hernioplasty prostheses. As far as hernia repair is concerned, bacterial contamination and tissue adhesion would be the clinical issues. Moreover, an optimal mesh should assist the healing process of hernia defect and avoid undesired prosthesis displacements. In this present study, the commercial hernia mesh was modified to solve the mentioned problems. Accordingly, a new bi-functional PP mesh with anti-adhesion and antibacterial properties on the front and adhesion properties (reduce undesired displacements) on the backside was prepared. The backside of PP mesh was coated with polycaprolactone (PCL) nanofibers modified by mussel-inspired L-3,4-dihydroxyphenylalanine (L-DOPA) bioadhesive. The front side was composed of two different nanofibrous mats, including hybrid and two-layered mats with different antibacterial properties, drug release, and biodegradation behavior, which were based on PCL nanofibers and biomacromolecule carboxyethyl-chitosan (CECS)/polyvinyl alcohol (PVA) nanofibers containing different ofloxacin amounts. The anti-adhesion, antibacterial, and biocompatibility studies were done through in-vitro experiments. The results revealed that DOPA coated PCL/PP/hybrid meshes containing ofloxacin below 20 wt% possessed proper cell viability, AdMSCs adhesion prevention, and excellent antibacterial efficiency. Moreover, DOPA modifications not only enhanced the surface properties of the PP mesh but also improved cell adhesion, spreading, and proliferation.

Nucleophilic Synthesis of 6-l-[18F]FDOPA. Is Copper-Mediated Radiofluorination the Answer?

Positron emission tomography employing 6-l-[18F]fluoro-3,4-dihydroxyphenylalanine (6-l-[18F]FDOPA) is currently a highly relevant clinical tool for detection of gliomas, neuroendocrine tumors and evaluation of Parkinson's disease progression. Yet, the deficiencies of electrophilic synthesis of 6-l-[18F]FDOPA hold back its wider use. To fulfill growing clinical demands for this radiotracer, novel synthetic strategies via direct nucleophilic 18F-radiloabeling starting from multi-Curie amounts of [18F]fluoride, have been recently introduced. In particular, Cu-mediated radiofluorination of arylpinacol boronates and arylstannanes show significant promise for introduction into clinical practice. In this short review these current developments will be discussed with a focus on their applicability to automation.

A New Ratiometric Fluorescent Probe for Specific Monitoring of hROS under Physiological Conditions Using Boric Acid-Protected l-DOPA Gold Nanoclusters.

The specific monitoring of physiological highly reactive oxygen species (hROS) using fluorescent gold nanoclusters (AuNCs) remains a challenge for scientists. Herein, SLB-AuNC was first synthesized via an ecofriendly one-pot method using starch as a template, l-3,4-dihydroxyphenylalanine (l-DOPA) as a reducing and a capping agent, and boric acid as a protecting agent for the catechol moiety of l-DOPA. The ingenious introduction of starch and boric acid enhanced the dispersibility, quantum yield, and photostability of fluorescent SLB-AuNCs. The obtained SLB-AuNCs possessed good monodispersity with an average diameter of 2.9 ± 0.8 nm and exhibited highly stable fluorescence with maximum emission at 480 nm under physiological conditions. A ratiometric fluorescent probe for hROS was developed through an oxidization-regulated Förster-resonance-energy-transfer process between SLB-AuNCs and 2,3-diaminophenazine (the oxidative product of hROS and o-phenylenediamine, with maximum fluorescence emission at 560 nm). With increasing amount of hROS, the outstanding fluorescence variation of the probe (I560 nm/I480 nm) enhanced about 300-fold, accompanied with a distinguishable color change from cyan to yellow. The detection limits of •OH, ClO-, and ONOO- were calculated as 0.11, 0.50, and 0.69 µM, respectively. High selectivity was achieved using o-phenylenediamine as a specific signal response for hROS to enable no interference reaction of other ROS toward SLB-AuNCs. The practicability of the proposed probe with super biocompatibility was evaluated by measuring exogenous and endogenous hROS levels in HeLa cells through fluorescence imaging. This work provides a novel strategy to design fluorescent AuNC probes for physiological hROS with great potential for the application of bioassay and bioimaging.

Peptide-mediated surface coatings for the release of wound-healing cytokines.

Supporting the wound healing process by sending the appropriate cytokine signals can shorten healing time and overcome chronic inflammation syndromes. Even though adhesion peptides consisting of Arg-Gly-Asp (RGD) are commonly used to enhance cell-surface interactions, peptide-mediated cytokine delivery has not been widely exploited so far. Cytokines interact with high affinity with their cognitive receptors but also with sulfated glycosaminoglycans (GAGs), both of which form a base for incorporation of cytokines into functional biomaterials. Here, we report on a mussel-derived surface coating as a prospective cytokine delivery system using covalently bound heparin mimetics, receptor-derived chemokine-binding peptides, and heparin-binding peptides (HBP). The latter enabled non-covalent immobilization of heparin on the surface followed by chemokine binding and release, whereas the former allowed direct non-covalent chemokine immobilization. The peptide displayed excellent binding to custom-made polystyrene 96-well plates, enabling convenient testing of several compounds. Released chemokine successfully induced migration in Jurkat cells, especially for the non-covalent heparin immobilization approach using HBPs as evaluated in a transwell assay. In comparison, heparin-mimetic coatings, comprised of sulfated peptides and GAG derivatives, proved less efficient with respect to amount of immobilized chemokine and migratory response. Thus, our study provides a roadmap for further rational optimization and translation into clinics.

Molecular design principles of Lysine-DOPA wet adhesion.

The mussel byssus has long been a source of inspiration for the adhesion community. Recently, adhesive synergy between flanking lysine (Lys, K) and 3,4-Dihydroxyphenylalanine (DOPA, Y) residues in the mussel foot proteins (Mfps) has been highlighted. However, the complex topological relationship of DOPA and Lys as well as the interfacial adhesive roles of other amino acids have been understudied. Herein, we study adhesion of Lys and DOPA-containing peptides to organic and inorganic substrates using single-molecule force spectroscopy (SMFS). We show that a modest increase in peptide length, from KY to (KY)3, increases adhesion strength to TiO2. Surprisingly, further increase in peptide length offers no additional benefit. Additionally, comparison of adhesion of dipeptides containing Lys and either DOPA (KY) or phenylalanine (KF) shows that DOPA is stronger and more versatile. We furthermore demonstrate that incorporating a nonadhesive spacer between (KY) repeats can mimic the hidden length in the Mfp and act as an effective strategy to dissipate energy.

PET Imaging of L-Type Amino Acid Transporter (LAT1) and Cystine-Glutamate Antiporter (xc-) with [18F]FDOPA and [18F]FSPG in Breast Cancer Models.

PURPOSE: The present study describes the analysis of amino acid transporters ASCT1, ASCT2, LAT1, and xc- in breast cancer under normoxic and hypoxic conditions. [18F]FDOPA-PET and [18F]FSPG-PET were used as imaging biomarkers to probe L-type amino acid transporter (LAT1) and cystine-glutamate antiporter (xc-) in breast cancer models. PROCEDURES: LAT1 and xc- transporters were studied under normoxic and hypoxic conditions with radiotracers [18F]FDOPA and [18F]FSPG in estrogen receptor-positive (ER+) MCF7 and triple-negative MDA-MB231 cells and in human mammary epithelial MCF10A control cells. Protein expression was analyzed using Western blot and immunohistochemistry. RESULTS: ASCT1 protein expression levels were comparable in all three cell lines, while noticeable ASCT2 expression levels were only found in MCF10A control cells. Higher LAT1 protein expression was detected in ER+ MCF7 cells. High xc- protein expression levels were detected in MDA-MB231 cells. Uptake of [18F]FDOPA through LAT1 was significantly higher in MCF7 versus MDA-MB231 cells, while the uptake of [18F]FSPG through xc- resulted in the opposite confirming expression and functional differences for both amino acid transporters in different breast cancer models. Hypoxia significantly increased [18F]FDOPA uptake in MCF7 cells and [18F]FSPG uptake in MDA-MB231 cells. In vivo PET imaging revealed substantially higher tumor uptake of [18F]FDOPA in MCF7 tumors as well as [18F]FSPG uptake in MDA-MB231 tumors confirming differences detected in vitro. CONCLUSIONS: ER+ breast cancer cells express higher levels of amino acid transporter LAT1, whereas triple-negative breast cancer cells express more xc-. Cellular uptake and PET imaging experiments with [18F]FDOPA and [18F]FSPG confirmed functional LAT1 and xc- expression profiles. There was initial evidence that hypoxia regulates the function of both amino acid transporters in breast cancer. The results further indicated that [18F]FDOPA and [18F]FSPG are suitable radiotracer to distinguish between ER+ and triple-negative breast cancer types.

Human IDH mutant 1p/19q co-deleted gliomas have low tumor acidity as evidenced by molecular MRI and PET: a retrospective study.

Co-deletion of 1p/19q is a hallmark of oligodendroglioma and predicts better survival. However, little is understood about its metabolic characteristics. In this study, we aimed to explore the extracellular acidity of WHO grade II and III gliomas associated with 1p/19q co-deletion. We included 76 glioma patients who received amine chemical exchange saturation transfer (CEST) imaging at 3 T. Magnetic transfer ratio asymmetry (MTRasym) at 3.0 ppm was used as the pH-sensitive CEST biomarker, with higher MTRasym indicating lower pH. To control for the confounder factors, T2 relaxometry and L-6-18F-fluoro-3,4-dihydroxyphenylalnine (18F-FDOPA) PET data were collected in a subset of patients. We found a significantly lower MTRasym in 1p/19q co-deleted gliomas (co-deleted, 1.17% ± 0.32%; non-co-deleted, 1.72% ± 0.41%, P = 1.13 × 10-7), while FDOPA (P = 0.92) and T2 (P = 0.61) were not significantly affected. Receiver operating characteristic analysis confirmed that MTRasym could discriminate co-deletion status with an area under the curve of 0.85. In analysis of covariance, 1p/19q co-deletion status was the only significant contributor to the variability in MTRasym when controlling for age and FDOPA (P = 2.91 × 10-3) or T2 (P = 8.03 × 10-6). In conclusion, 1p/19q co-deleted gliomas were less acidic, which may be related to better prognosis. Amine CEST-MRI may serve as a non-invasive biomarker for identifying 1p/19q co-deletion status.