Affibody molecules for in vivo characterization of HER2-positive tumors by near-infrared imaging

Affimer reagents enable targeted delivery of therapeutic agents and RNA via virus-like particles

Monoclonal antibodies have revolutionized therapies, but non-immunoglobulin scaffolds are becoming compelling alternatives owing to their adaptability. Their ability to be labeled with imaging or cytotoxic compounds and to create multimeric proteins is an attractive strategy for therapeutics. Focusing on HER2, a frequently overexpressed receptor in breast cancer, this study addresses some limitations of conventional targeting moieties by harnessing the potential of these scaffolds. HER2-binding Affimers were isolated and characterized, demonstrating potency as binding reagents and efficient internalization by HER2-overexpressing cells. Affimers conjugated with cytotoxic agent achieved dose-dependent reductions in cell viability within HER2-overexpressing cell lines. Bispecific Affimers, targeting HER2 and virus-like particles, facilitated efficient internalization of virus-like particles carrying enhanced green fluorescent protein (eGFP)-encoding RNA, leading to protein expression. Anti-HER2 affibody or designed ankyrin repeat protein (DARPin) fusion constructs with the anti-VLP Affimer further underscore the adaptability of this approach. This study demonstrates the versatility of scaffolds for precise delivery of cargos into cells, advancing biotechnology and therapeutic research.

Rapid Generation of Therapeutic Nanoparticles Using Cell-Free Expression Systems

The surface modification of membrane-based nanoparticles, such as liposomes, polymersomes, and lipid nanoparticles, with targeting molecules, such as binding proteins, is an important step in the design of therapeutic materials. However, this modification can be costly and time-consuming, requiring cellular hosts for protein expression and lengthy purification and conjugation steps to attach proteins to the surface of nanocarriers, which ultimately limits the development of effective protein-conjugated nanocarriers. Here, the use of cell-free protein synthesis systems to rapidly create protein-conjugated membrane-based nanocarriers is demonstrated. Using this approach, multiple types of functional binding proteins, including affibodies, computationally designed proteins, and scFvs, can be cell-free expressed and conjugated to liposomes in one-pot. The technique can be expanded further to other nanoparticles, including polymersomes and lipid nanoparticles, and is amenable to multiple conjugation strategies, including surface attachment to and integration into nanoparticle membranes. Leveraging these methods, rapid design of bispecific artificial antigen presenting cells and enhanced delivery of lipid nanoparticle cargo in vitro is demonstrated. It is envisioned that this workflow will enable the rapid generation of membrane-based delivery systems and bolster our ability to create cell-mimetic therapeutics.

Indocyanine green dye and its application in gastrointestinal surgery: The future is bright green

Indocyanine green (ICG) is a water-soluble fluorescent dye that is minimally toxic and widely used in gastrointestinal surgery. ICG facilitates anatomical identification of structures (e.g., ureters), assessment of lymph nodes, biliary mapping, organ perfusion and anastomosis assessment, and aids in determining the adequacy of oncological margins. In addition, ICG can be conjugated to artificially created antibodies for tumour markers, such as carcinoembryonic antigen for colorectal, breast, lung, and gastric cancer, prostate-specific antigen for prostate cancer, and cancer antigen 125 for ovarian cancer. Although ICG has shown promising results, the optimization of patient factors, dye factors, equipment, and the method of assessing fluorescence intensity could further enhance its utility. This review summarizes the clinical application of ICG in gastrointestinal surgery and discusses the emergence of novel dyes such as ZW-800 and VM678 that have demonstrated appropriate pharmacokinetic properties and improved target-to-background ratios in animal studies. With the emergence of robotic technology and the increasing reporting of ICG utility, a comprehensive review of clinical application of ICG in gastrointestinal surgery is timely and this review serves that aim.

Photothermal Therapy with HER2-Targeted Silver Nanoparticles Leading to Cancer Remission

Nanoparticles exhibiting the localized surface plasmon resonance (LSPR) phenomenon are promising tools for diagnostics and cancer treatment. Among widely used metal nanoparticles, silver nanoparticles (Ag NPs) possess the strongest light scattering and surface plasmon strength. However, the therapeutic potential of Ag NPs has until now been underestimated. Here we show targeted photothermal therapy of solid tumors with 35 nm HER2-targeted Ag NPs, which were produced by the green synthesis using an aqueous extract of Lavandula angustifolia Mill. Light irradiation tests demonstrated effective hyperthermic properties of these NPs, namely heating by 10 °C in 10 min. To mediate targeted cancer therapy, Ag NPs were conjugated to the scaffold polypeptide, affibody ZHER2:342, which recognizes a clinically relevant oncomarker HER2. The conjugation was mediated by the PEG linker to obtain Ag-PEG-HER2 nanoparticles. Flow cytometry tests showed that Ag-PEG-HER2 particles successfully bind to HER2-overexpressing cells with a specificity comparable to that of full-size anti-HER2 IgGs. A confocal microscopy study showed efficient internalization of Ag-PEG-HER2 into cells in less than 2 h of incubation. Cytotoxicity assays demonstrated effective cell death upon exposure to Ag-PEG-HER2 and irradiation, caused by the production of reactive oxygen species. Xenograft tumor therapy with Ag-PEG-HER2 particles in vivo resulted in full primary tumor regression and the prevention of metastatic spread. Thus, for the first time, we have shown that HER2-directed plasmonic Ag nanoparticles are effective sensitizers for targeted photothermal oncotherapy.

Bioengineering of virus-like particles as dynamic nanocarriers for in vivo delivery and targeting to solid tumours

Virus-like particles (VLPs) are known as self-assembled, non-replicative and non-infectious protein particles, which imitate the formation and structure of original wild type viruses, however, lack the viral genome and/or their fragments. The capacity of VLPs to encompass small molecules like nucleic acids and others has made them as novel vessels of nanocarriers for drug delivery applications. In addition, VLPs surface have the capacity to achieve variation of the surface display via several modification strategies including genetic modification, chemical modification, and non-covalent modification. Among the VLPs nanocarriers, Hepatitis B virus core (HBc) particles have been the most encouraging candidate. HBc particles are hollow nanoparticles in the range of 30-34 nm in diameter and 7 nm thick envelopes, consisting of 180 or 240 copies of identical polypeptide monomer. They also employ a distinctive position among the VLPs carriers due to the high-level synthesis, which serves as a strong protective capsid shell and efficient self-assembly properties. This review highlights on the bioengineering of HBc particles as dynamic nanocarriers for in vivo delivery and specific targeting to solid tumours.

Combinatorial in silico and in vivo evaluation of immune response elicitation by the affibody ZHER2

Due to the high affinity for binding to target molecules and also other unique attributes, affibodies have a great potential to be used in immunotherapeutic and diagnostic approaches. However, the possibility of undesirable immune response is still a great concern. In the current study, we investigated the possible antigenicity, allergenicity and cytotoxicity of the HER2-targeting affibody Z_HER2. The binding affinity of potential epitopes of the affibody to murine major histocompatibility complex (MHC) molecules was investigated by immunoinformatics tools and docking approaches. The possible interaction of Z_HER2 with human leukocyte antigens HLA-DP, HLA-DM, HLA-DQ and HLA-DR was also studied by protein-protein docking. Additionally, the synthesized affibody gene was expressed and the protein was purified for boosted immunization of Balb/c mice. Induced secretion of IFN-γ, IL-2, IL-4 and IL-10, and total serum IgG were assessed in the immunized mice. Furthermore, MTT cell viability test was performed to evaluate the cytotoxicity of Z_HER2 in splenocytes of the treated mice. In silico analyses showed the possible induction of the immune response by Z_HER2. While the affibody could elicit the secretion of cellular immune cytokines, it could not induce a significant humoral response in the treated mice and did not show any cytotoxic effects on the exposed splenocytes. These findings explain the practicability of Z_HER2 for therapeutic and in vivo diagnostic usages, though its ubiquitous application may need more studies.

Combination of Near-Infrared Photoimmunotherapy Using Trastuzumab and Small Protein Mimetic for HER2-Positive Breast Cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer (IR700Dye) that is activated by near-infrared light irradiation. We previously reported on the use of NIR-PIT with a small protein mimetic, the Affibody molecule (6–7 kDa), instead of a monoclonal antibody. In this study, we investigated a combination of NIR-PIT for HER2-positive breast cancer cells (SK-BR3, MDA-MB361, and JIMT1) with HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate. HER2 Affibody and trastuzumab target different epitopes of the HER2 protein and do not compete. In vitro, the combination of NIR-PIT using both HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate induced necrotic cell death of HER2-positive breast cancer cells without damage to HER2-negative breast cancer cells (MCF7). It was more efficient than NIR-PIT using either the HER2 Affibody-IR700Dye conjugate alone or the trastuzumab-IR700Dye conjugate alone. Additionally, this combination of NIR-PIT was significantly effective against HER2 low-expressing cancer cells, trastuzumab-resistant cells (JIMT1), and brain metastatic cells of breast cancer (MDA-MB361). Furthermore, in vivo imaging exhibited the strong fluorescence intensity of both HER2 Affibody-IR700Dye conjugates and trastuzumab-Alexa488 conjugates in HER2-positive tumor, indicating that both HER2 Affibody and trastuzumab specifically bind to HER2-positive tumors without competing with each other. In conclusion, the combination of NIR-PIT using both HER2 Affibody and trastuzumab expands the targeting scope of NIR-PIT for HER2-positive breast cancer.

Evaluation of Near-infrared Fluorescence-conjugated Peptides for Visualization of Human Epidermal Receptor 2-overexpressed Gastric Cancer

Purpose

A near-infrared (NIR) fluorescence imaging is a promising tool for cancer-specific image guided surgery. Human epidermal receptor 2 (HER2) is one of the candidate markers for gastric cancer. In this study, we aimed to synthesize HER2-specific NIR fluorescence probes and evaluate their applicability in cancer-specific image-guided surgeries using an animal model.

Materials and Methods

An NIR dye emitting light at 800 nm (IRDye800CW; Li-COR) was conjugated to trastuzumab and an HER2-specific affibody using a click mechanism. HER2 affinity was assessed using surface plasmon resonance. Gastric cancer cell lines (NCI-N87 and SNU-601) were subcutaneously implanted into female BALB/c nu (6–8 weeks old) mice. After intravenous injection of the probes, biodistribution and fluorescence signal intensity were measured using Lumina II (Perkin Elmer) and a laparoscopic NIR camera (InTheSmart).

Results

Trastuzumab-IRDye800CW exhibited high affinity for HER2 (K_D=2.093(3) pM). Fluorescence signals in the liver and spleen were the highest at 24 hours post injection, while the signal in HER2-positive tumor cells increased until 72 hours, as assessed using the Lumina II system. The signal corresponding to the tumor was visually identified and clearly differentiated from the liver after 72 hours using a laparoscopic NIR camera. Affibody-IRDye800CW also exhibited high affinity for HER2 (K_D=4.71 nM); however, the signal was not identified in the tumor, probably owing to rapid renal clearance.

Conclusions

Trastuzumab-IRDye800CW may be used as a potential NIR probe that can be injected 2–3 days before surgery to obtain high HER2-specific signal and contrast. Affibody-based NIR probes may require modifications to enhance mobilization to the tumor site.

PLGA Nanoparticles Decorated with Anti-HER2 Affibody for Targeted Delivery and Photoinduced Cell Death

The effect of enhanced permeability and retention is often not sufficient for highly effective cancer therapy with nanoparticles, and the development of active targeted drug delivery systems based on nanoparticles is probably the main direction of modern cancer medicine. To meet the challenge, we developed polymer PLGA nanoparticles loaded with fluorescent photosensitive xanthene dye, Rose Bengal, and decorated with HER2-recognizing artificial scaffold protein, affibody Z_HER2:342. The obtained 170 nm PLGA nanoparticles possess both fluorescent and photosensitive properties. Namely, under irradiation with the green light of 540 nm nanoparticles, they produced reactive oxygen species leading to cancer cell death. The chemical conjugation of PLGA with anti-HER2 affibody resulted in the selective binding of nanoparticles only to HER2-overexpressing cancer cells. HER2 is a receptor tyrosine kinase that belongs to the EGFR/ERbB family and is overexpressed in 30% of breast cancers, thus serving as a clinically relevant oncomarker. However, the standard targeting molecules such as full-size antibodies possess serious drawbacks, such as high immunogenicity and the need for mammalian cell production. We believe that the developed affibody-decorated targeted photosensitive PLGA nanoparticles will provide new solutions for ongoing problems in cancer diagnostics and treatment, as well in cancer theranostics.

pH-Controlled Protein Orthogonal Ligation Using Asparaginyl Peptide Ligases

Peptide asparaginyl ligases (PALs) catalyze transpeptidation at the Asn residue of a short Asn-Xaa₁-Xaa₂ tripeptide motif. Due to their high catalytic activity toward the P1-Asn substrates at around neutral pH, PALs have been used extensively for peptide ligation at asparaginyl junctions. PALs also bind to aspartyl substrates, but only when the ^γCOOH of P1-Asp remains in its neutral, protonated form, which usually requires an acidic pH. However, this limits the availability of the amine nucleophile and, consequently, the ligation efficiency at aspartyl junctions. Because of this perceived inefficiency, the use of PALs for Asp-specific ligation remains largely unexplored. We found that PAL enzymes, such as VyPAL2, display appreciable catalytic activities toward P1-Asp substrates at pH 4-5, which are at least 2 orders of magnitude higher than that of sortase A, making them practically useful for both intra- and intermolecular ligations. This also allows sequential ligations, first at Asp and then at Asn junctions, because the newly formed aspartyl peptide bond is resistant to the ligase at the pH used for asparaginyl ligation in the second step. Using this pH-controlled orthogonal ligation method, we dually labeled truncated sfGFP with a cancer-targeting peptide and a doxorubicin derivative at the respective N- and C-terminal ends in the N-to-C direction. In addition, a fluorescein tag and doxorubicin derivative were tagged to an EGFR-targeting affibody in the C-to-N direction. This study shows that the pH-dependent catalytic activity of PAL enzymes can be exploited to prepare multifunction protein biologics for pharmacological applications.

The feasibility of folate receptor alpha- and HER2-targeted intraoperative fluorescence-guided cytoreductive surgery in women with epithelial ovarian cancer: A systematic review

BACKGROUND

Epithelial ovarian cancer (EOC) is often diagnosed late, with a 5-year relative survival of 30.2% for patients with metastatic disease. Residual disease following cytoreductive surgery is an important predictor for poor survival. EOC is characterized by diffuse peritoneal metastases and depositions of small size, challenging a complete resection. Targeted fluorescence imaging is a technique to enhance tumor visualization and can be performed intraoperatively. Folate receptor alpha (FRα) and human epidermal growth factor receptor 2 (HER2) are overexpressed in EOC in 80% and 20% of the cases, respectively, and have been previously studied as a target for intraoperative imaging.

OBJECTIVE

To systematically review the literature on the feasibility of FRα and HER2 targeted fluorescence-guided cytoreductive surgery (FGCS) in women with EOC.

METHODS

PubMed and Embase were searched for human and animal studies on FGCS targeting either HER2 or FRα in either women with EOC or animal models of EOC. Risk of bias and methodological quality were assessed with the SYRCLE and MINORS tool, respectively.

RESULTS

All animal studies targeting either FRα or HER2 were able to detect tumor deposits using intraoperative fluorescence imaging. One animal study targeting HER2 compared conventional cytoreductive surgery (CCS) to FGCS and concluded that FGCS, either without or following CCS, resulted in statistically significant less residual disease compared to CCS alone. Human studies on FGCS showed an increased detection rate of tumor deposits. True positives ranged between 75%-77% and false positives between 10%-25%. Lymph nodes were the main source of false positive results. Sensitivity was 85.9%, though only reported by one human study.

CONCLUSION

FGCS targeting either HER2 or FRα appears to be feasible in both EOC animal models and patients with EOC. FGCS is a promising technique, but further research is warranted to validate these results and particularly study the survival benefit.

Engineering protein theranostics using bio-orthogonal asparaginyl peptide ligases

Background: Protein theranostics integrate both diagnostic and treatment functions on a single disease-targeting protein. However, the preparation of these multimodal agents remains a major challenge. Ideally, conventional recombinant proteins should be used as starting materials for modification with the desired detection and therapeutic functionalities, but simple chemical strategies that allow the introduction of two different modifications into a protein in a site-specific manner are not currently available. We recently discovered two highly efficient peptide ligases, namely butelase-1 and VyPAL2. Although both ligate at asparaginyl peptide bonds, these two enzymes are bio-orthogonal with distinguishable substrate specificities, which can be exploited to introduce distinct modifications onto a protein.

Methods: We quantified substrate specificity differences between butelase-1 and VyPAL2, which provide orthogonality for a tandem ligation method for protein dual modifications. Recombinant proteins or synthetic peptides engineered with the preferred recognition motifs of butelase-1 and VyPAL2 at their respective C- and N-terminal ends could be modified consecutively by the action of the two ligases.

Results: Using this method, we modified an EGFR-targeting affibody with a fluorescein tag and a mitochondrion-lytic peptide at its respective N- and C-terminal ends. The dual-labeled protein was found to be a selective bioimaging and cytotoxic agent for EGFR-positive A431 cancer cells. In addition, the method was used to prepare a cyclic form of the affibody conjugated with doxorubicin. Both modified affibodies showed increased cytotoxicity to A431 cells by 10- and 100-fold compared to unconjugated doxorubicin and the free peptide, respectively.

Conclusion: Bio-orthogonal tandem ligation using two asparaginyl peptide ligases with differential substrate specificities is a straightforward approach for the preparation of multifunctional protein biologics as potential theranostics.

[68Ga]ABY-028: an albumin-binding domain (ABD) protein-based imaging tracer for positron emission tomography (PET) studies of altered vascular permeability and predictions of albumin-drug conjugate transport

Background

Albumin is commonly used as a carrier platform for drugs to extend their circulatory half-lives and influence their uptake into tissues that have altered permeability to the plasma protein. The albumin-binding domain (ABD) protein, which binds in vivo to serum albumin with high affinity, has proven to be a versatile scaffold for engineering biopharmaceuticals with a range of binding capabilities. In this study, the ABD protein equipped with a mal-DOTA chelator (denoted ABY-028) was radiolabeled with gallium-68 (⁶⁸Ga). This novel radiotracer was then used together with positron emission tomography (PET) imaging to examine variations in the uptake of the ABD-albumin conjugate with variations in endothelial permeability.

Results

ABY-028, produced by peptide synthesis in excellent purity and stored at − 20 °C, was stable for 24 months (end of study). [⁶⁸Ga]ABY-028 could be obtained with labeling yields of > 80% and approximately 95% radiochemical purity. [⁶⁸Ga]ABY-028 distributed in vivo with the plasma pool, with highest radioactivity in the heart ventricles and major vessels of the body, a gradual transport over time from the circulatory system into tissues and elimination via the kidneys. Early [⁶⁸Ga]ABY-028 uptake differed in xenografts with different vascular properties: mean standard uptake values (SUV_mean) were initially 5 times larger in FaDu than in A431 xenografts, but the difference decreased to 3 after 1 h. Cutaneously administered, vasoactive nitroglycerin increased radioactivity in the A431 xenografts. Heterogeneity in the levels and rates of increases of radioactivity uptake was observed in sub-regions of individual MMTV-PyMT mammary tumors and in FaDu xenografts. Higher uptake early after tracer administration could be observed in lower metabolic regions. Fluctuations in the increased permeability for the tracer across the blood-brain-barrier (BBB) direct after experimentally induced stroke were monitored by PET and the increased uptake was confirmed by ex vivo phosphorimaging.

Conclusions

[⁶⁸Ga]ABY-028 is a promising new tracer for visualization of changes in albumin uptake due to disease- and pharmacologically altered vascular permeability and their potential effects on the passive uptake of targeting therapeutics based on the ABD protein technology.

[Ribosome display: Evolution and acellular selection of molecular libraries for high affinity binder generation]

Ribosome display is a powerful method for selection and molecular evolution of proteins and peptides from large libraries. Displayed proteins are recovered from target molecules in multiple rounds of selection in order to enrich specific binders with the desired properties. Nowadays, ribosome display has become one of the most widely-used display technologies thanks to its advantages over cell-display as phage display. Ribosome display is an in vitro method, in which a stable ternary complex is formed between the mRNA, the ribosome and the nascent protein. A selection cycle can be performed in a few days and bacterial transformation is not necessary. Ribosome display has been used to screen and select peptides, proteins or molecular scaffolds in order to increase their affinity, specificity, catalytic activity or stability. In this review, ribosome display systems and their applications in selection and evolution of proteins are described.

Cytotoxicity evaluation of curcumin-loaded affibody-decorated liposomes against breast cancerous cell lines

Curcumin is known as an effective anticancer herbal medicine but unfortunately, its bioavailability is poor which necessitate efforts for developing more efficient and specific delivery systems. Human epidermal growth factor receptor 2 (HER 2) due to its overexpression in various types of cancers, is demonstrated to be a good candidate as a target for anticancer therapy. In this study, cytotoxicity of curcumin encapsulated in ZHER2:342 Affibody-decorated liposome was investigated against SKBR3 and MCF-7 cancerous cell lines. Curcumin-containing liposomes were prepared from soybeans lecetin and cholesterol by thin-film hydration method. Affibody ZHER2:342 molecules via C-terminal cysteine residue were conjugated covalently to the prepared liposomes. Particle size analysis was performed using atomic force microscopy (AFM) and dynamic light scattering (DLS). Curcumin loading was measured using UV-Vis spectrophotometry and cytotoxic activity of curcumin formulations against cancerous cell lines was investigated by MTT assay. Induction of apoptosis was investigated using flow cytometry through Annexin V staining. Particle analysis showed the formation of spherical liposomes with a mean diameter of about 150 nm. Cytotoxic activity of curcumin was improved by its encapsulation in both liposomes and affibody-decorated liposomes. The Annexin V staining indicated the induction of apoptosis by affibody-decorated liposomes in both MCF-7 and SKBR3 cells. Decoration of curcumin-loaded liposomes with affibody ZHER2:342 may improve curcumin apoptotic function independently of HER2 expression level.

Affibody-Conjugated RALA Polymers Delivering Oligomeric 5-Fluorodeoxyuridine for Targeted Therapy of HER2 Overexpressing Gastric Cancer

Affibody-conjugated RALA (affi-RA) are designed for delivering oligomeric 5-fluorodeoxyuridine (FUdR, metabolite of 5-FU) strand to raise the selectivity of 5-fluorouracil (5-FU), decrease its toxicity and improve its suboptimal therapeutic efficacy. The nanodrugs, FUdR@affi-RA, are spontaneously assembled by electrostatic interaction between positively charged affi-RA and negatively charged FUdR₁₅ -strands (15 consecutive FUdR). FUdR@affi-RA exhibits excellent stability under simulated physiological conditions. Compared with free FUdR, FUdR@affi-RA shows excellent targeting and higher cytotoxicity in human epidermal growth factor receptor 2 (HER2) overexpressing gastric cancer N87 cells. Moreover, the anticancer mechanism studies reveal that FUdR@affi-RA enhances the expression and activity of apoptosis-associated proteins in the Bcl-2/Bax-caspase 8,9-caspase 3 apoptotic pathway induced by FUdR. This study indicates that the fusion vector, affi-RA, presents a promising delivery system platform for nucleoside analogue drugs and provides a new strategy for the development of therapeutics of cancer treatment.

PET Imaging of HER2-Positive Tumors with Cu-64-Labeled Affibody Molecules

PURPOSE

Previous studies has demonstrated the utility of human epidermal growth factor receptor type 2 (HER2) as an attractive target for cancer molecular imaging and therapy. An affibody protein with strong binding affinity for HER2, Z_HER2:342, has been reported. Various methods of chelator conjugation for radiolabeling HER2 affibody molecules have been described in the literature including N-terminal conjugation, C-terminal conjugation, and other methods. Cu-64 has recently been extensively evaluated due to its half-life, decay properties, and availability. Our goal was to optimize the radiolabeling method of this affibody molecule with Cu-64, and translate a positron emission tomography (PET) probe with the best in vivo performance to clinical PET imaging of HER2-positive cancers.

PROCEDURES

In our study, three anti-HER2 affibody proteins-based PET probes were prepared, and their in vivo performance was evaluated in mice bearing HER2-positive subcutaneous SKOV3 tumors. The affibody analogues, Ac-Cys-Z_HER2:342, Ac-Z_HER2:342(Cys³⁹), and Ac-Z_HER2:342-Cys, were synthesized using the solid phase peptide synthesis method. The purified small proteins were site-specifically conjugated with the maleimide-functionalized chelator, 1,4,7,10-tetraazacyclododecane-1,4,7-tris- aceticacid-10-maleimidethylacetamide (maleimido-mono-amide-DOTA). The resulting DOTA-affibody conjugates were then radiolabeled with Cu-64. Cell uptake assay of the resulting PET probes, [⁶⁴Cu]DOTA-Cys-Z_HER2:342, [⁶⁴Cu]DOTA-Z_HER2:342(Cys³⁹), and [⁶⁴Cu]DOTA-Z_HER2:342-Cys, was performed in HER2-positive human ovarian SKOV3 carcinoma cells at 4 and 37 °C. The binding affinities of the radiolabeled peptides were tested by cell saturation assay using SKOV3 cells. PET imaging, biodistribution, and metabolic stability studies were performed in mice bearing SKOV3 tumors.

RESULTS

Cell uptake assays showed high and specific uptake by incubation of Cu-64-labeled affibodies with SKOV3 cells. The affinities (K_D) of the PET radio probes as tested by cell saturation analysis were in the low nanomolar range with the ranking of [⁶⁴Cu]DOTA-Cys-Z_HER2:342 (25.2 ± 9.2 nM) ≈ [⁶⁴Cu]DOTA-Z_HER2:342-Cys (32.6 ± 14.7 nM) > [⁶⁴Cu]DOTA-Z_HER2:342(Cys³⁹) (77.6 ± 22.2 nM). In vitro stability and in vivo metabolite analysis study revealed that all three probes were stable enough for in vivo imaging applications, while [⁶⁴Cu]DOTA-Cys-Z_HER2:342 showed the highest stability. In vivo small-animal PET further demonstrated fast tumor targeting, good tumor accumulation, and good tumor to normal tissue contrast of all three probes. For [⁶⁴Cu]DOTA-Cys-Z_HER2:342, [⁶⁴Cu]DOTA-Z_HER2:342(Cys³⁹), and [⁶⁴Cu]DOTA-Z_HER2:342-Cys, tumor uptake at 24 h are 4.0 ± 1.0 % ID/g, 4.0 ± 0.8 %ID/g, and 4.3 ± 0.7 %ID/g, respectively (mean ± SD, n = 4). Co-injection of the probes with non-labeled anti-HER2 affibody proteins confirmed in vivo specificities of the compounds by tumor uptake reduction.

CONCLUSIONS

The three Cu-64-labeled Z_HER2:342 analogues all display excellent HER2 targeting ability and tumor PET imaging quality. Although varied in the position of the radiometal labeling of these three Cu-64-labeled Z_HER2:342 analogues, there is no significant difference in tumor and normal tissue uptakes among the three probes. [⁶⁴Cu]DOTA-Cys-Z_HER2:342 stands out as the most superior PET probe because of its highest affinities and in vivo stability.

Generation of novel affibody molecules targeting the EBV LMP2A N-terminal domain with inhibiting effects on the proliferation of nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) induced by latent infection with Epstein-Barr virus (EBV) remains the most common head and neck cancer in Southeast Asia, especially in the southern part of China. It is well known that persistent expression of two EBV latent membrane proteins (LMP1/LMP2A) plays a key role in nasopharyngeal carcinogenesis. Therefore, the therapeutic approach of targeting the LMP1/LMP2A protein and subsequently blocking the LMP1/LMP2A-mediated signalling pathway has been considered for treating patients with NPC. Recently, affibody molecules, a new class of small (~6.5 kDa) affinity proteins, have been confirmed to be powerful generalisable tools for developing imaging or therapeutic agents by targeting specific molecules. In this study, three EBV LMP2A N-terminal domain-binding affibody molecules (ZLMP2A-N85, ZLMP2A-N110 and ZLMP2A-N252) were identified by screening a phage-displayed peptide library, and their high affinity and specificity for the EBV LMP2A N-terminal domain were confirmed by surface plasmon resonance (SPR), indirect immunofluorescence, co-immunoprecipitation and near-infrared small animal fluorescence imaging in vitro and in vivo. Moreover, affibody molecules targeting the EBV LMP2A N-terminal domain significantly reduced the viability of the EBV-positive cell lines C666-1, CNE-2Z and B95-8. Further investigations showed that affibody ZLMP2A-N110 could inhibit the phosphorylation of AKT, GSK-3β and β-catenin signalling proteins, leading to suppression of β-catenin nuclear translocation and subsequent inhibition of c-Myc oncogene expression, which may be responsible for the reduced viability of NPC-derived cell lines. In conclusion, our findings provide a strong evidence that three novel EBV LMP2A N-terminal domain-binding affibody molecules have great potential for utilisation and development as agents for both molecular imaging and targeted therapy of EBV-related NPC.

Enhancing Antitumor Efficacy of Nucleoside Analog 5-Fluorodeoxyuridine on HER2-Overexpressing Breast Cancer by Affibody-Engineered DNA Nanoparticle

BACKGROUND

Chemotherapy, as an adjuvant treatment strategy for HER2-positive breast cancer, can effectively improve clinical symptoms and overcome the drug resistance of therapeutic monoclonal antibodies. Nucleoside analogues are a class of traditional chemotherapeutic drugs that are widely applied in adjuvant therapy. However, there are many critical issues that limit their clinical efficiency, including poor selectivity and stability, severe side effects and suboptimal therapeutic efficacy. Hence, this work aims to develop a new DNA nanocarrier for targeted drug delivery to solve the above problems.

METHODS

Four 41-mer DNA strands were synthesized and 10 FUdR molecules were attached to 5' end of each DNA strand by DNA solid-phase synthesis. An affibody molecule was connected to the end of polymeric FUdR through a linker in one of the four strands. The affibody-FUdR-tetrahedral DNA nanostructures (affi-F/TDNs) were self-assembled through four DNA strands, in which one vertex was connected to an affibody at the end of a polymeric FUdR tail and three vertices were only polymeric FUdR tails. In vitro cellular uptake of affi-F/TDNs was examined visually with confocal fluorescence microscopy and flow cytometry, and the cytotoxicity of affi-F/TDNs against cancer cells was investigated with MTT assay. Cell apoptosis was detected by Annexin V-FITC/PI double staining method. Using NOD/SCID (Mus Musculus) mice model, the targeted killing efficacy of affi-F/TDNs was also evaluated.

RESULTS

The drug-loading of FUdR in affi-TDNs was 19.6% in mole ratio. The in vitro results showed that affi-F/TDNs had high selectivity and inhibition (81.2%) for breast cancer BT474 cells overexpressing HER2 and low toxicity in MCF-7 cells with low HER2 expression. During the in vivo application, affi-F/TDNs displayed good stability in the blood circulation, achieved specific accumulation in tumor region and the best antitumor efficacy (inhibition ratio of 58.1%), and showed excellent biocompatibility.

CONCLUSIONS

The affibody-DNA tetrahedrons, as a simple and effective active targeting delivery nanocarrier, provided a new avenue for the transport of nucleoside antitumor drugs.

Multivalent HER2-binding polymer conjugates facilitate rapid endocytosis and enhance intracellular drug delivery

Incorporating targeting moieties that recognize cancer-specific cellular markers can enhance specificity of anticancer nanomedicines. The HER2 receptor is overexpressed on numerous cancers, making it an attractive target. However, unlike many receptors that trigger endocytosis upon ligand binding, HER2 is an internalization-resistant receptor. As most chemotherapeutics act on intracellular targets, this presents a significant challenge for exploiting HER2 overexpression for improved tumor killing. However, hyper-crosslinking of HER2 has been shown to override the receptor's native behavior and trigger internalization. This research co-opts this crosslinking-mediated internalization for efficient intracellular delivery of an anticancer nanomedicine - specifically a HPMA copolymer-based drug delivery system. This polymeric carrier was conjugated with a small (7 kDa) HER2-binding affibody peptide to produce a panel of polymer-affibody conjugates with valences from 2 to 10 peptides per polymer chain. The effect of valence on surface binding and uptake was evaluated separately. All conjugates demonstrated similar (nanomolar) binding affinity towards HER2-positive ovarian carcinoma cells, but higher-valence conjugates induced more rapid endocytosis, with over 90% of the surface-bound conjugate internalized within 4 h. Furthermore, this enhancement was sensitive to crowding - high surface loading reduced conjugates' ability to crosslink receptors. Collectively, this evidence strongly supports a crosslinking-mediated endocytosis mechanism. Lead candidates from this panel achieved high intracellular delivery even at picomolar treatment concentrations; untargeted HPMA copolymers required 1000-fold higher treatment concentrations to achieve similar levels of intracellular accumulation. This increased intracellular delivery also translated to a more potent nanomedicine against HER2-positive cells; incorporation of the chemotherapeutic paclitaxel into this targeted carrier enhanced cytotoxicity over untargeted polymer-drug conjugate.

Near-Infrared Photoimmunotherapy Using a Small Protein Mimetic for HER2-Overexpressing Breast Cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a new and promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer which is activated by near-infrared light irradiation, causing cell death. We investigated NIR-PIT using a small protein mimetic (6-7 kDa), Affibody molecules, instead of a monoclonal antibody for HER2-overexpressing cancer. Because of its small size, the Affibody has rapid clearance, high imaging contrast, and good tumor penetration. Due to the small size of the Affibodies, which can cross the blood-brain barrier, NIR-PIT using Affibodies has the potential to extend the target cancer of NIR-PIT, including brain metastases. In vitro, NIR-PIT using HER2 Affibody-IR700Dye conjugates induced the selective destruction of HER2-overexpressing breast cancer cells without damage to control cells having low level expression of HER2. HER2-overexpressing cancer cells showed necrotic cell death and their viability maintained at low levels, even 5 days after NIR-PIT. In contrast, treatment with high concentration of HER2 Affibody-IR700Dye conjugate alone or irradiation with high dose of NIR light alone was without effect on cell viability. Affibody and IR700Dye are currently used clinically, and therefore, we would expect the current formulation to be safely and quickly transitioned into clinical trials.

Review of fluorescent steroidal ligands for the estrogen receptor 1995-2018

The development of fluorescent ligands for the estrogen receptor (ER) continues to be of interest. Over the past 20 years, most efforts have focused on appending an expanding variety of fluorophores to the B-, C- and D-rings of the steroidal scaffold. This review highlights the synthesis and evaluation of derivatives substituted primarily at the 6-, 7α- and 17α-positions, culminating with our recent work on 11β-substituted estradiols, and proposes an approach to new fluorescent imaging agents that retain high ER affinity.

Targeted Drug Delivery and Image-Guided Therapy of Heterogeneous Ovarian Cancer Using HER2-Targeted Theranostic Nanoparticles

Cancer heterogeneity and drug resistance limit the efficacy of cancer therapy. To address this issue, we have developed an integrated treatment protocol for effective treatment of heterogeneous ovarian cancer. Methods: An amphiphilic polymer coated magnetic iron oxide nanoparticle was conjugated with near infrared dye labeled HER2 affibody and chemotherapy drug cisplatin. The effects of the theranostic nanoparticle on targeted drug delivery, therapeutic efficacy, non-invasive magnetic resonance image (MRI)-guided therapy, and optical imaging detection of therapy resistant tumors were examined in an orthotopic human ovarian cancer xenograft model with highly heterogeneous levels of HER2 expression. Results: We found that systemic delivery of HER2-targeted magnetic iron oxide nanoparticles carrying cisplatin significantly inhibited the growth of primary tumor and peritoneal and lung metastases in the ovarian cancer xenograft model in nude mice. Differential delivery of theranostic nanoparticles into individual tumors with heterogeneous levels of HER2 expression and various responses to therapy were detectable by MRI. We further found a stronger therapeutic response in metastatic tumors compared to primary tumors, likely due to a higher level of HER2 expression and a larger number of proliferating cells in metastatic tumor cells. Relatively long-time retention of iron oxide nanoparticles in tumor tissues allowed interrogating the relationship between nanoparticle drug delivery and the presence of resistant residual tumors by in vivo molecular imaging and histological analysis of the tumor tissues. Following therapy, most of the remaining tumors were small, primary tumors that had low levels of HER2 expression and nanoparticle drug accumulation, thereby explaining their lack of therapeutic response. However, a few residual tumors had HER2-expressing tumor cells and detectable nanoparticle drug delivery but failed to respond, suggesting additional intrinsic resistant mechanisms. Nanoparticle retention in the small residual tumors, nevertheless, produced optical signals for detection by spectroscopic imaging. Conclusion: The inability to completely excise peritoneal metastatic tumors by debulking surgery as well as resistance to chemotherapy are the major clinical challenges for ovarian cancer treatment. This targeted cancer therapy has the potential for the development of effective treatment for metastatic ovarian cancer.

Supramolecular Nanofibers of Drug-Peptide Amphiphile and Affibody Suppress HER2+ Tumor Growth

Antibody-based medicines and nanomedicines are very promising for cancer therapy due to the high specificity and efficacy of antibodies. However, antibody-drug conjugates and antibody-modified nanomaterials frequently suffer from low drug loading and loss of functions due to the covalent modification of the antibody. A novel and versatile strategy to prepare supramolecular nanomaterials by the coassembly of an affibody (antiHER2) and drug-peptide amphiphiles is reported here. During the enzyme-instructed self-assembly process, the drug-peptide amphiphile can coassemble with the affibody, resulting in supramolecular nanofibers in hydrogels. The drug loading in the supramolecular nanofibers is high (>30 wt%), and the stability of antiHER2 is significantly improved in the nanofibers at 37 °C (>15 d in vitro). The supramolecular nanofibers exhibit high affinity for HER2+ cancer cells and can be efficiently taken up by these cells. In a mouse tumor model, the supramolecular nanofibers abolish HER2+ NCI-N87 tumor growth due to the good accumulation and retention of nanofibers in tumor. This study provides a novel strategy to prepare nanomedicines with high drug loading and high specificity.

A novel HPV16 E7-affitoxin for targeted therapy of HPV16-induced human cervical cancer

Cervical cancer, the second most common cause of cancer death in women worldwide, is significantly associated with infection of high-risk human papillomaviruses (HPVs), especially the most common genotype, HPV 16. To date, there is no established noninvasive therapy to treat cervical cancer.

Methods: Here, we report a novel affitoxin that targets HPV16 E7 protein, one of the primary target proteins in molecular targeted therapy for HPV-induced cervical cancer. The affitoxin, Z_HPV16E7 affitoxin384 was generated by fusing the modified Pseudomonas Exotoxin A (PE38KDEL) to the HPV16 E7-specific affibody. The expressed and purified Z_HPV16E7 affitoxin384 was characterized using numerous methods. SPR assay, indirect immunofluorescence assay, and near-infrared (NIR) optical imaging were respectively performed to assess the targeting ability of Z_HPV16E7 affitoxin384 to HPV16 E7 protein both in vitro and in vivo. Cell viability assays and SiHa tumor-bearing nude mice were used to evaluate the efficacy of Z_{HPV16 E7} affitoxin384 in vitro and in vivo, respectively.

Results: Using in vitro methods the SPR assay and indirect immunofluorescence assay showed that Z_HPV16E7 affitoxin384 targeted HPV16 E7 with high binding affinity and specificity. Significant reduction of cell viability in HPV16 positive cells was observed in the presence of Z_{HPV16 E7} affitoxin384. By NIR optical imaging, Z_{HPV16 E7} affitoxin384 specifically targeted HPV16 positive tumors in vivo. Z_HPV16E7 affitoxin384 showed significant in vivo antitumor efficacy in two kinds of tumor-bearing nude mouse models.

Conclusions: Z_HPV16E7 affitoxin384 is a potent anti-cervical cancer therapeutic agent that could be effective against HPV16 positive tumors in humans.

Targeted peptide-Au cluster binds to epidermal growth factor receptor (EGFR) in both active and inactive states: a clue for cancer inhibition through dual pathways

The epidermal growth factor receptor (EGFR) has become an important target protein in anticancer drug development. Meanwhile, peptide-Au cluster has been proposed as potential targeted nano-drug assembled by targeting peptide. Here, we designed and synthesized a novel peptide-Au cluster as Au₁₀Peptide₅ to target to EGFR. We found Au₁₀Peptide₅ could target to the natural binding sites of all EGFRs at membrane in both active and inactive states by molecular simulations. Its targeted ability was further verified by the co-localization and blocking experiments. We also study the configuration modifications of both active and inactive EGFRs after binding by Au₁₀Peptide₅. For active EGFR, the absorbed Au₁₀Peptide₅ might replace the natural ligand in EGFR endocytosis process. Then, the peptide-Au cluster in endochylema could inhibit the cancer relating enzyme activity including thioredoxin reductase1 (TrxR1) and induce the oxidative stress mediated apoptosis in tumor cells. For inactive EGFR, it was retained in inactive state by Au₁₀Peptide₅ binding to inhibit dimerization of EGFR for anticancer. Both pathways might be applied in anticancer drug development based on the theoretical and experimental study here.

Fluorescent Affibody Molecule Administered In Vivo at a Microdose Level Labels EGFR Expressing Glioma Tumor Regions

Purpose

Fluorescence guidance in surgical oncology provides the potential to realize enhanced molecular tumor contrast with dedicated targeted tracers, potentially with a microdose injection level. For most glioma tumors, the blood brain barrier is compromised allowing some exogenous drug/molecule delivery and accumulation for imaging. The aberrant overexpression and/or activation of epidermal growth factor receptor (EGFR) is associated with many types of cancers, including glioblastoma, and so the use of a near-infrared (NIR) fluorescent molecule targeted to the EGFR receptor provides the potential for improving tumor contrast during surgery. Fluorescently labeled affibody molecule (ABY-029) has high EGFR affinity and high potential specificity with reasonably fast plasma clearance. In this study, ABY-29 was evaluated in glioma versus normal brain uptake from intravenous injection at a range of doses, down to a microdose injection level.

Procedure

Nude rats were inoculated with the U251 human glioma cell line in the brain. Tumors were allowed to grow for 3–4 weeks. ABY-029 fluorescence ex vivo imaging of brain slices was acquired at different time points (1–48 h) and varying injection doses from 25 to 122 μg/kg (from human protein microdose equivalent to five times microdose levels).

Results

The tumor was most clearly visualized at 1-h post-injection with 8- to 16-fold average contrast relative to normal brain. However, the tumor still could be identified after 48 h. In all cases, the ABY-029 fluorescence appeared to localize preferentially in EGFR-positive regions. Increasing the injected dose from a microdose level to five times, a microdose level increased the signal by 10-fold, and the contrast was from 8 to 16, showing that there was value in doses slightly higher than the microdose restriction. Normal tissue uptake was found to be affected by the tumor size, indicating that edema was a likely factor affecting the expected tumor to normal tissue contrast.

Conclusion

These results suggest that the NIR-labeled affibody molecules provide an excellent potential to increase surgical visualization of EGFR-positive tumor regions.

Beyond Antibodies as Binding Partners: The Role of Antibody Mimetics in Bioanalysis

The emergence of novel binding proteins or antibody mimetics capable of binding to ligand analytes in a manner analogous to that of the antigen-antibody interaction has spurred increased interest in the biotechnology and bioanalytical communities. The goal is to produce antibody mimetics designed to outperform antibodies with regard to binding affinities, cellular and tumor penetration, large-scale production, and temperature and pH stability. The generation of antibody mimetics with tailored characteristics involves the identification of a naturally occurring protein scaffold as a template that binds to a desired ligand. This scaffold is then engineered to create a superior binder by first creating a library that is then subjected to a series of selection steps. Antibody mimetics have been successfully used in the development of binding assays for the detection of analytes in biological samples, as well as in separation methods, cancer therapy, targeted drug delivery, and in vivo imaging. This review describes recent advances in the field of antibody mimetics and their applications in bioanalytical chemistry, specifically in diagnostics and other analytical methods.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Next generation NIR fluorophores for tumor imaging and fluorescence-guided surgery: A review

Cancer is a group of diseases responsible for the major causes of mortality and morbidity among people of all ages. Even though medical sciences have made enormous growth, complete treatment of this deadly disease is still a challenging task. Last few decades witnessed an impressive growth in the design and development of near infrared (NIR) fluorophores with and without recognition moieties for molecular recognitions, imaging and image guided surgeries. The present article reviews recently reported NIR emitting organic/inorganic fluorophores that targets and accumulates in organelle/organs specifically for molecular imaging of cancerous cells. Near infrared (NIR probe) with or without a tumor-targeting warhead have been considered and discussed for their applications in the field of cancer imaging. In addition, challenges persist in this area are also delineated in this review.

A Conjugate Based on Anti-HER2 Diaffibody and Auristatin E Targets HER2-Positive Cancer Cells

Antibody-drug conjugates (ADCs) have recently emerged as efficient and selective cancer treatment therapeutics. Currently, alternative forms of drug carriers that can replace monoclonal antibodies are under intensive investigation. Here, a cytotoxic conjugate of an anti-HER2 (Human Epidermal Growth Factor Receptor 2) diaffibody with monomethyl-auristatin E (MMAE) is proposed as a potential anticancer therapeutic. The anti-HER2 diaffibody was based on the Z_HER2:4 affibody amino acid sequence. The anti-HER2 diaffibody has been expressed as a His-tagged protein in E. coli and purified by Ni-nitrilotriacetyl (Ni-NTA) agarose chromatography. The molecule was properly folded, and the high affinity and specificity of its interaction with HER2 was confirmed by surface plasmon resonance (SPR) and flow cytometry, respectively. The (Z_HER2:4)₂DCS-MMAE conjugate was obtained by coupling the maleimide group linked with MMAE to cysteines, which were introduced in a drug conjugation sequence (DCS). Cytotoxicity of the conjugate was evaluated using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide MTT assay and the xCELLigence Real-Time Cell Analyzer. Our experiments demonstrated that the conjugate delivered auristatin E specifically to HER2-positive tumor cells, which finally led to their death. These results indicate that the cytotoxic diaffibody conjugate is a highly potent molecule for the treatment of various types of cancer overexpressing HER2 receptors.

Affibody-targeted fluorogen activating protein for in vivo tumor imaging

Molecular imaging using near-infrared (NIR) fluorescence is useful for intraoperative imaging and real-time margin identification. Directly conjugated IR dyes possess useful properties for in vivo imaging, but conjugation often substantially alters the circulation dynamics of targeting moieties. We developed and characterized a new tumor-targeting probe, affiFAP, which consists of a protein that specifically binds EGFR (affibody) and a fluorogen activating protein (FAP). This compact molecular recognition reagent can reversibly bind and activate fluorescence of otherwise nonfluorescent dyes and allows tumor visualization with low nonspecific tissue staining. We demonstrate molecular pre-targeting of affiFAPs and subsequent systemic or topical application of fluorogenic dye to achieve high contrast, fast clearance, and good tissue penetration that may be used in clinical settings to molecularly define tumor margins.

Optical imaging probes in oncology

Cancer is a complex disease, characterized by alteration of different physiological molecular processes and cellular features. Keeping this in mind, the possibility of early identification and detection of specific tumor biomarkers by non-invasive approaches could improve early diagnosis and patient management.Different molecular imaging procedures provide powerful tools for detection and non-invasive characterization of oncological lesions. Clinical studies are mainly based on the use of computed tomography, nuclear-based imaging techniques and magnetic resonance imaging. Preclinical imaging in small animal models entails the use of dedicated instruments, and beyond the already cited imaging techniques, it includes also optical imaging studies. Optical imaging strategies are based on the use of luminescent or fluorescent reporter genes or injectable fluorescent or luminescent probes that provide the possibility to study tumor features even by means of fluorescence and luminescence imaging. Currently, most of these probes are used only in animal models, but the possibility of applying some of them also in the clinics is under evaluation.The importance of tumor imaging, the ease of use of optical imaging instruments, the commercial availability of a wide range of probes as well as the continuous description of newly developed probes, demonstrate the significance of these applications. The aim of this review is providing a complete description of the possible optical imaging procedures available for the non-invasive assessment of tumor features in oncological murine models. In particular, the characteristics of both commercially available and newly developed probes will be outlined and discussed.

Intraoperative mapping of sentinel lymph node metastases using a clinically translated ultrasmall silica nanoparticle

The management of regional lymph nodes in patients with melanoma has undergone a significant paradigm shift over the past several decades, transitioning from the use of more aggressive surgical approaches, such as lymph node basin dissection, to the application of minimally invasive sentinel lymph node (SLN) biopsy methods to detect the presence of nodal micrometastases. SLN biopsy has enabled reliable, highly accurate, and low-morbidity staging of regional lymph nodes in early stage melanoma as a means of guiding treatment decisions and improving patient outcomes. The accurate identification and staging of lymph nodes is an important prognostic factor, identifying those patients for whom the expected benefits of nodal resection outweigh attendant surgical risks. However, currently used standard-of-care technologies for SLN detection are associated with significant limitations. This has fueled the development of clinically promising platforms that can serve as intraoperative visualization tools to aid accurate and specific determination of tumor-bearing lymph nodes, map cancer-promoting biological properties at the cellular/molecular levels, and delineate nodes from adjacent critical structures. Among a number of promising cancer-imaging probes that might facilitate achievement of these ends is a first-in-kind ultrasmall tumor-targeting inorganic (silica) nanoparticle, designed to overcome translational challenges. The rationale driving these considerations and the application of this platform as an intraoperative treatment tool for guiding resection of cancerous lymph nodes is discussed and presented within the context of alternative imaging technologies. WIREs Nanomed Nanobiotechnol 2016, 8:535-553. doi: 10.1002/wnan.1380 For further resources related to this article, please visit the WIREs website.

Emerging optical methods for surveillance of Barrett's oesophagus

The rapid rise in incidence of oesophageal adenocarcinoma has motivated the need for improved methods for surveillance of Barrett's oesophagus. Early neoplasia is flat in morphology and patchy in distribution and is difficult to detect with conventional white light endoscopy (WLE). Light offers numerous advantages for rapidly visualising the oesophagus, and advanced optical methods are being developed for wide-field and cross-sectional imaging to guide tissue biopsy and stage early neoplasia, respectively. We review key features of these promising methods and address their potential to improve detection of Barrett's neoplasia. The clinical performance of key advanced imaging technologies is reviewed, including (1) wide-field methods, such as high-definition WLE, chromoendoscopy, narrow-band imaging, autofluorescence and trimodal imaging and (2) cross-sectional techniques, such as optical coherence tomography, optical frequency domain imaging and confocal laser endomicroscopy. Some of these instruments are being adapted for molecular imaging to detect specific biological targets that are overexpressed in Barrett's neoplasia. Gene expression profiles are being used to identify early targets that appear before morphological changes can be visualised with white light. These targets are detected in vivo using exogenous probes, such as lectins, peptides, antibodies, affibodies and activatable enzymes that are labelled with fluorescence dyes to produce high contrast images. This emerging approach has potential to provide a 'red flag' to identify regions of premalignant mucosa, outline disease margins and guide therapy based on the underlying molecular mechanisms of cancer progression.

Development of Follicle-Stimulating Hormone Receptor Binding Probes to Image Ovarian Xenografts

The Follicle-Stimulating Hormone Receptor (FSHR) is used as an imaging biomarker for the detection of ovarian cancer (OC). FSHR is highly expressed on ovarian tumors and involved with cancer development and metastatic signaling pathways. A decapeptide specific to the FSHR extracellular domain is synthesized and conjugated to fluorescent dyes to image OC cells in vitro and tumors xenograft model in vivo. The in vitro binding curve and the average number of FSHR per cell are obtained for OVCAR-3 cells by a high resolution flow cytometer. For the decapeptide, the measured EC50 was 160 μM and the average number of receptors per cell was 1.7 × 10⁷. The decapeptide molecular imaging probe reached a maximum tumor to muscle ratio five hours after intravenous injection and a dose-dependent plateau after 24-48 hours. These results indicate the potential application of a small molecular weight imaging probe specific to ovarian cancer through binding to FSHR. Based on these results, multimeric constructs are being developed to optimize binding to ovarian cells and tumors.

Structure-based Design of Peptides with High Affinity and Specificity to HER2 Positive Tumors

To identify peptides with high affinity and specificity against human epidermal growth factor receptor 2 (HER2), a series of peptides were designed based on the structure of HER2 and its Z(HER2:342) affibody. By using a combination protocol of molecular dynamics modeling, MM/GBSA binding free energy calculations, and binding free energy decomposition analysis, two novel peptides with 27 residues, pep27 and pep27-24M, were successfully obtained. Immunocytochemistry and flow cytometry analysis verified that both peptides can specifically bind to the extracellular domain of HER2 protein at cellular level. The Surface Plasmon Resonance imaging (SPRi) analysis showed that dissociation constants (K D) of these two peptides were around 300 nmol/L. Furthermore, fluorescence imaging of peptides against nude mice xenografted with SKBR3 cells indicated that both peptides have strong affinity and high specificity to HER2 positive tumors.

Optical imaging of ovarian cancer using HER-2 affibody conjugated nanoparticles

Computed Tomography (CT), Ultrasound (US), and Magnetic Resonance Imaging (MRI) have been the mainstay of clinical imaging regimens for the detection of ovarian cancer. However, without tumor specific contrast enhancement, these imaging modalities lack specificity and sensitivity in the detection of small primary and disseminated tumors in the peritoneal cavity. Herein, we illustrate a fairly new near infrared (NIR) optical imaging approach developed in our laboratory for the noninvasive detection of ovarian tumors using a HER-2 targeted nanoparticle-based imaging agent in an orthotopic mouse model of ovarian cancer. We used multimodal imaging approaches to detect the disease accurately and rapidly by utilizing a single imaging agent, NIR dye-labeled HER-2 affibody conjugated iron oxide nanoparticles. This agent targets HER-2 receptors, which are overexpressed in ovarian tumors. This chapter outlines materials and methods for the: (1) production of HER-2 targeted nanoparticles; (2) establishment of an orthotopic human ovarian cancer xenograft model; (3) monitoring of tumor growth by bioluminescence imaging; (4) administration of targeted nanoparticles followed by NIR optical imaging for the detection of orthotopic ovarian cancers with targeted accumulation of the nanoparticle imaging probes.

Fluorogen activating protein-affibody probes: modular, no-wash measurement of epidermal growth factor receptors

Fluorescence is essential for dynamic live cell imaging, and affinity reagents are required for quantification of endogenous proteins. Various fluorescent dyes can report on different aspects of biological trafficking, but must be independently conjugated to affinity reagents and characterized for specific biological readouts. Here we present the characterization of a new modular platform for small anti-EGFR affinity probes for studying rapid changes in receptor pools. A protein domain (FAP _dL5**) that binds to malachite-green (MG) derivatives for fluorescence activation was expressed as a recombinant fusion to one or two copies of the compact EGFR binding affibody Z_EGFR:1907. This is a recombinant and fluorogenic labeling reagent for native EGFR molecules. In vitro fluorescence assays demonstrated that the binding of these dyes to the FAP–affibody fusions produced thousand-fold fluorescence enhancements, with high binding affinity and fast association rates. Flow cytometry assays and fluorescence microscopy demonstrated that these probes label endogenous EGFR on A431 cells without disruption of EGFR function, and low nanomolar surface K_d values were observed with the double-Z_EGFR:1907 constructs. The application of light-harvesting fluorogens (dyedrons) significantly improved the detected fluorescence signal. Altering the order of addition of the ligand, probe, and dyes allowed differentiation between surface and endocytotic pools of receptors to reveal the rapid dynamics of endocytic trafficking. Therefore, FAP/affibody coupling provides a new approach to construct compact and modular affinity probes that label endogenous proteins on living cells and can be used for studying rapid changes in receptor pools involved in trafficking.

Intraoperative imaging-guided cancer surgery: from current fluorescence molecular imaging methods to future multi-modality imaging technology

Cancer is a major threat to human health. Diagnosis and treatment using precision medicine is expected to be an effective method for preventing the initiation and progression of cancer. Although anatomical and functional imaging techniques such as radiography, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) have played an important role for accurate preoperative diagnostics, for the most part these techniques cannot be applied intraoperatively. Optical molecular imaging is a promising technique that provides a high degree of sensitivity and specificity in tumor margin detection. Furthermore, existing clinical applications have proven that optical molecular imaging is a powerful intraoperative tool for guiding surgeons performing precision procedures, thus enabling radical resection and improved survival rates. However, detection depth limitation exists in optical molecular imaging methods and further breakthroughs from optical to multi-modality intraoperative imaging methods are needed to develop more extensive and comprehensive intraoperative applications. Here, we review the current intraoperative optical molecular imaging technologies, focusing on contrast agents and surgical navigation systems, and then discuss the future prospects of multi-modality imaging technology for intraoperative imaging-guided cancer surgery.

Quantitative comparison of tumor delivery for multiple targeted nanoparticles simultaneously by multiplex ICP-MS

Given the rapidly expanding library of disease biomarkers and targeting agents, the number of unique targeted nanoparticles is growing exponentially. The high variability and expense of animal testing often makes it unfeasible to examine this large number of nanoparticles in vivo. This often leads to the investigation of a single formulation that performed best in vitro. However, nanoparticle performance in vivo depends on many variables, many of which cannot be adequately assessed with cell-based assays. To address this issue, we developed a lanthanide-doped nanoparticle method that allows quantitative comparison of multiple targeted nanoparticles simultaneously. Specifically, superparamagnetic iron oxide (SPIO) nanoparticles with different targeting ligands were created, each with a unique lanthanide dopant. Following the simultaneous injection of the various SPIO compositions into tumor-bearing mice, inductively coupled plasma mass spectroscopy was used to quantitatively and orthogonally assess the concentration of each SPIO composition in serial blood and resected tumor samples.