Autoradiography: high-resolution molecular imaging in pharmaceutical discovery and development

Pharmacokinetics of monoclonal antibodies locally-applied into the middle ear of guinea pigs

Countless therapeutic antibodies are currently available for the treatment of a broad range of diseases. Some target molecules of therapeutic antibodies are involved in the pathogenesis of sensorineural hearing loss (SNHL), suggesting that SNHL may be a novel target for monoclonal antibody (mAb) therapy. When considering mAb therapy for SNHL, understanding of the pharmacokinetics of mAbs after local application into the middle ear is crucial. To reveal the fundamental characteristics of mAb pharmacokinetics following local application into the middle ear of guinea pigs, we performed pharmacokinetic analyses of mouse monoclonal antibodies to FLAG-tag (FLAG-mAbs), which have no specific binding sites in the middle and inner ear. FLAG-mAbs were rapidly transferred from the middle ear to the cochlear fluid, indicating high permeability of the round window membrane to mAbs. FLAG-mAbs were eliminated from the cochlear fluid 3 h after application, similar to small molecules. Whole-body autoradiography and quantitative assessments of cerebrospinal fluid and serum demonstrated that the biodistribution of FLAG-mAbs was limited to the middle and inner ear. Altogether, the pharmacokinetics of mAbs are similar to those of small molecules when locally applied into the middle ear, suggesting the necessity of drug delivery systems for appropriate mAb delivery to the cochlear fluid after local application into the middle ear.

Blind Image Restoration Enhances Digital Autoradiographic Imaging of Radiopharmaceutical Tissue Distribution

Digital autoradiography (DAR) is a powerful tool to quantitatively determine the distribution of a radiopharmaceutical within a tissue section and is widely used in drug discovery and development. However, the low image resolution and significant background noise can result in poor correlation, even errors, between radiotracer distribution, anatomical structure, and molecular expression profiles. Differing from conventional optical systems, the point spread function (PSF) in DAR is determined by properties of radioisotope decay, phosphor and digitizer. Calibration of an experimental PSF a priori is difficult, prone to error, and impractical. We have developed a content-adaptive restoration algorithm to address these problems. Methods: We model the DAR imaging process using a mixed Poisson-Gaussian model, and blindly restore the image by a Penalized Maximum-Likelihood Expectation-Maximization algorithm (PG- PEM). PG-PEM implements a patch-based estimation algorithm with "Density-Based Spatial Clus- tering of Applications with Noise" to estimate noise parameters, and utilizes L2 and Hessian Frobenius (HF) norms as regularization functions to improve performance. Results: First, PG-PEM outperformed other restoration algorithms at the denoising task (p<0.01). Next, we implemented PG-PEM on pre-clinical DAR images (¹⁸F-FDG treated mice tumor and heart, ¹⁸F-NaF treated mice femur) and clinical DAR images (bone biopsy sections from ²²³RaCl2 treated castrate resistant prostate cancer patients). DAR images restored by PG-PEM of all samples achieved significantly higher effective resolution, contrast to noise ratio (CNR), and a lower standard deviation of background (STDB) (p<0.0001). Additionally, by comparing the registration results between the clinical DAR images and the segmented bone masks from the corresponding histological images, the radiopharmaceutical distribution was significantly improved (p<0.0001). Conclusion: PG-PEM is able to increase resolution and contrast while robustly accounting for DAR noise, and demonstrates the capacity to be widely implemented to improve pre- and clinical DAR imaging of radiopharmaceutical distribution.

Visualizing topical drug uptake with conventional fluorescence microscopy and deep learning

Mapping the uptake of topical drugs and quantifying dermal pharmacokinetics (PK) presents numerous challenges. Though high resolution and high precision methods such as mass spectrometry offer the means to quantify drug concentration in tissue, these tools are complex and often expensive, limiting their use in routine experiments. For the many topical drugs that are naturally fluorescent, tracking fluorescence emission can be a means to gather critical PK parameters. However, skin autofluorescence can often overwhelm drug fluorescence signatures. Here we demonstrate the combination of standard epi-fluorescence imaging with deep learning for the visualization and quantification of fluorescent drugs in human skin. By training a U-Net convolutional neural network on a dataset of annotated images, drug uptake from both high "infinite" dose and daily clinical dose regimens can be measured and quantified. This approach has the potential to simplify routine topical product development in the laboratory.

Radiolabeling of amide functionalized multi-walled carbon nanotubes for bioaccumulation study in fish bone using whole-body autoradiography

Commercial and medicinal applications of functionalized carbon nanotubes (f-CNTs) such as amidated f-CNTs are expanding rapidly with a potential risk exposure to living organisms. The effects of amidated f-CNTs on aquatic species have received a limited attention. In this work, an easy wet method to prepare [¹⁴C]-label amide multi-walled carbon nanotubes (MWNTs) is reported. Labeled carbon nanotubes were prepared by successive reactions of carboxylation, chloroacylation, and final amidation using [¹⁴C]-labeled ethanolamine. The f-CNTs were characterized using elemental analysis, electron dispersive X-ray, transmission electron microscopy, thermogravimetric analysis, and Raman and FTIR spectroscopy. An uptake experiment was carried out with juvenile Arctic char (Salvelinus alpinus) using water dispersed amidated [¹⁴C]-f-CNTs to assess their biodistribution in fish tissues using whole body autoradiography. The radioactivity pattern observed in fish head suggests that f-CNTs were accumulated in head bone canals, possibly involving an interaction with mineral or organic phases of bones such as calcium and collagen. This f-CNTs distribution illustrates how important is to consider the surface charges of functionalized carbon nanotubes in ecotoxicological studies.

18F-FDG-PET in Mouse Models of Alzheimer's Disease

Suitable animal models and in vivo biomarkers are essential for development and evaluation of new therapeutic strategies in Alzheimer's disease (AD). ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG)-positron-emission tomography (PET) is an imaging biomarker that allows the assessment of cerebral glucose metabolism in vivo. While ¹⁸F-FDG-PET/CT is an established tool in the evaluation of AD patients, its role in preclinical studies with AD mouse models remains unclear. Here, we want to review available studies on ¹⁸F-FDG-PET/CT in AD mouse models in order to evaluate the method and its impact in preclinical AD research. Only a limited number of studies using ¹⁸F-FDG-PET in AD mice were carried out so far showing contradictory findings in cerebral FDG uptake. Methodological differences as well as underlying pathological features of used mouse models seem to be accountable for those varying results. However, ¹⁸F-FDG-PET can be a valuable tool in longitudinal in vivo therapy monitoring with a lot of potential for future studies.

Current and Emerging Preclinical Approaches for Imaging-Based Characterization of Atherosclerosis

Atherosclerotic plaques can remain quiescent for years, but become life threatening upon rupture or disruption, initiating clot formation in the vessel lumen and causing acute myocardial infarction and ischemic stroke. Whether and how a plaque ruptures is determined by its macroscopic structure and microscopic composition. Rupture-prone plaques usually consist of a thin fibrous cap with few smooth muscle cells, a large lipid core, a dense infiltrate of inflammatory cells, and neovessels. Such lesions, termed high-risk plaques, can remain asymptomatic until the thrombotic event. Various imaging technologies currently allow visualization of morphological and biological characteristics of high-risk atherosclerotic plaques. Conventional protocols are often complex and lack specificity for high-risk plaque. Conversely, new imaging approaches are emerging which may overcome these limitations. Validation of these novel imaging techniques in preclinical models of atherosclerosis is essential for effective translational to clinical practice. Imaging the vessel wall, as well as its biological milieu in small animal models, is challenging because the vessel wall is a small structure that undergoes continuous movements imposed by the cardiac cycle as it is adjacent to circulating blood. The focus of this paper is to provide a state-of-the-art review on techniques currently available for preclinical imaging of atherosclerosis in small animal models and to discuss the advantages and limitations of each approach.

Alpha particle autoradiography for high spatial resolution mapping of radionuclides

An autoradiographic technique capable of determining the spatial location of radioactive isotopes within materials on the scale of micrometers is demonstrated in low-activity mineral samples, where the concentrations of radionuclides with short half lives is small and below the detection limits of current measurement techniques. The location of certain radionuclide species within samples with complex structures on the micron scale can yield valuable information, however current methods do not have the spatial resolution required for this purpose. We demonstrate the use of an autoradiographic emulsion to directly image alpha particle events in samples with low radionuclide concentrations, allowing spatial resolution of radionuclide locations on the order of several microns. Exposure over a long time period allows sufficient integration of decay events enabling analysis of samples with low activity but large area, (less than 1×10^-4 Bq/mm²). The use of polarising filters to increase contrast between the alpha particle tracks and the substrate during imaging demonstrates the viability of the technique on samples with a complex structure.

Application of modern autoradiography to nuclear forensic analysis

Modern autoradiography techniques based on phosphorimaging technology using image plates (IPs) and digital scanning can identify heterogeneities in activity distributions and reveal material properties, serving to inform subsequent analyses. Here, we have adopted these advantages for applications in nuclear forensics, the technical analysis of radioactive or nuclear materials found outside of legal control to provide data related to provenance, production history, and trafficking route for the materials. IP autoradiography is a relatively simple, non-destructive method for sample characterization that records an image reflecting the relative intensity of alpha and beta emissions from a two-dimensional surface. Such data are complementary to information gathered from radiochemical characterization via bulk counting techniques, and can guide the application of other spatially resolved techniques such as scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). IP autoradiography can image large 2-dimenstional areas (up to 20×40cm), with relatively low detection limits for actinides and other radioactive nuclides, and sensitivity to a wide dynamic range (10⁵) of activity density in a single image. Distributions of radioactivity in nuclear materials can be generated with a spatial resolution of approximately 50μm using IP autoradiography and digital scanning. While the finest grain silver halide films still provide the best possible resolution (down to ∼10μm), IP autoradiography has distinct practical advantages such as shorter exposure times, no chemical post-processing, reusability, rapid plate scanning, and automated image digitization. Sample preparation requirements are minimal, and the analytical method does not consume or alter the sample. These advantages make IP autoradiography ideal for routine screening of nuclear materials, and for the identification of areas of interest for subsequent micro-characterization methods. In this paper we present a summary of our setup, as modified for nuclear forensic sample analysis and related research, and provide examples of data from select samples from the nuclear fuel cycle and historical nuclear test debris.

Deuterium- and Tritium-Labelled Compounds: Applications in the Life Sciences

Hydrogen isotopes are unique tools for identifying and understanding biological and chemical processes. Hydrogen isotope labelling allows for the traceless and direct incorporation of an additional mass or radioactive tag into an organic molecule with almost no changes in its chemical structure, physical properties, or biological activity. Using deuterium-labelled isotopologues to study the unique mass-spectrometric patterns generated from mixtures of biologically relevant molecules drastically simplifies analysis. Such methods are now providing unprecedented levels of insight in a wide and continuously growing range of applications in the life sciences and beyond. Tritium (³ H), in particular, has seen an increase in utilization, especially in pharmaceutical drug discovery. The efforts and costs associated with the synthesis of labelled compounds are more than compensated for by the enhanced molecular sensitivity during analysis and the high reliability of the data obtained. In this Review, advances in the application of hydrogen isotopes in the life sciences are described.

Null functions in three-dimensional imaging of alpha and beta particles

Null functions of an imaging system are functions in the object space that give exactly zero data. Hence, they represent the intrinsic limitations of the imaging system. Null functions exist in all digital imaging systems, because these systems map continuous objects to discrete data. However, the emergence of detectors that measure continuous data, e.g. particle-processing (PP) detectors, has the potential to eliminate null functions. PP detectors process signals produced by each particle and estimate particle attributes, which include two position coordinates and three components of momentum, as continuous variables. We consider Charged-Particle Emission Tomography (CPET), which relies on data collected by a PP detector to reconstruct the 3D distribution of a radioisotope that emits alpha or beta particles, and show empirically that the null functions are significantly reduced for alpha particles if ≥3 attributes are measured or for beta particles with five attributes measured.

Discrepancy Between Tumor Antigen Distribution and Radiolabeled Antibody Binding in a Nude Mouse Xenograft Model of Human Melanoma

OBJECTIVES

Biodistribution of antibodies is vital to successful immunoscintigraphy/immunotherapy, and it is assumed to be similar to antigen distribution. We measured and compared the binding pattern of radiolabeled antibody to tissue antigen distribution in a nude mouse xenograft model of human melanoma.

METHODS

We transplanted 10⁷ FEM-XII human melanoma cells into the right flank of five nude mice. For the control, we transplanted 5 × 10⁶ LS174T human colon cancer cells into the left flank. Two weeks later, 10 μCi of ¹³¹I-labeled melanoma-associated 96.5 monoclonal antibody (targeting p97 antigen) was intravenously injected. Three days later, we sacrificed the mice and evaluated 96.5 antibody binding and concentration in the tumors by ex vivo quantitative autoradiography (QAR). Two months later, we incubated adjacent tumor tissue slices in various concentrations of ¹²⁵I-labeled 96.5 MoAb and evaluated the distribution/concentration of p97 antigen by in vitro QAR.

RESULTS

p97 antigen distribution was homogeneous in the tumors (total antigen concentration [Bmax] = 17.36-38.36 pmol/g). In contrast, radiolabeled 96.5 antibody binding was heterogenous between location within the tumor (estimated bound antigen concentration = 0.7-6.6 pmol/g). No quantifiable parameters were found to be related with radiolabeled antibody binding and tumor antigen distribution. Antibody-bound tumor antigen to total antigen ratios ranged between 2% and 38%.

CONCLUSIONS

Heterogeneous features of target antibody binding were observed in contrast to relatively homogenous feature of tumor antigen. We did not identify any correlations between p97 antigen distribution and 96.5 antibody binding in melanoma tissue. Radiolabeled 96.5 antibody binding patterns within melanoma cannot be predicted based on p97 antigen distribution in the tumor, which needs to be further studied with several other methods and more subjects in the future.

Exemplifying the Screening Power of Mass Spectrometry Imaging over Label-Based Technologies for Simultaneous Monitoring of Drug and Metabolite Distributions in Tissue Sections

Mass spectrometry imaging (MSI) provides pharmaceutical researchers with a suite of technologies to screen and assess compound distributions and relative abundances directly from tissue sections and offer insight into drug discovery–applicable queries such as blood-brain barrier access, tumor penetration/retention, and compound toxicity related to drug retention in specific organs/cell types. Label-free MSI offers advantages over label-based assays, such as quantitative whole-body autoradiography (QWBA), in the ability to simultaneously differentiate and monitor both drug and drug metabolites. Such discrimination is not possible by label-based assays if a drug metabolite still contains the radiolabel. Here, we present data exemplifying the advantages of MSI analysis. Data of the distribution of AZD2820, a therapeutic cyclic peptide, are related to corresponding QWBA data. Distribution of AZD2820 and two metabolites is achieved by MSI, which [14C]AZD2820 QWBA fails to differentiate. Furthermore, the high mass-resolving power of Fourier transform ion cyclotron resonance MS is used to separate closely associated ions.

Future technology insight: mass spectrometry imaging as a tool in drug research and development

In pharmaceutical research, understanding the biodistribution, accumulation and metabolism of drugs in tissue plays a key role during drug discovery and development. In particular, information regarding pharmacokinetics, pharmacodynamics and transport properties of compounds in tissues is crucial during early screening. Historically, the abundance and distribution of drugs have been assessed by well-established techniques such as quantitative whole-body autoradiography (WBA) or tissue homogenization with LC/MS analysis. However, WBA does not distinguish active drug from its metabolites and LC/MS, while highly sensitive, does not report spatial distribution. Mass spectrometry imaging (MSI) can discriminate drug and its metabolites and endogenous compounds, while simultaneously reporting their distribution. MSI data are influencing drug development and currently used in investigational studies in areas such as compound toxicity. In in vivo studies MSI results may soon be used to support new drug regulatory applications, although clinical trial MSI data will take longer to be validated for incorporation into submissions. We review the current and future applications of MSI, focussing on applications for drug discovery and development, with examples to highlight the impact of this promising technique in early drug screening. Recent sample preparation and analysis methods that enable effective MSI, including quantitative analysis of drugs from tissue sections will be summarized and key aspects of methodological protocols to increase the effectiveness of MSI analysis for previously undetectable targets addressed. These examples highlight how MSI has become a powerful tool in drug research and development and offers great potential in streamlining the drug discovery process.

In situ drug and metabolite analysis [corrected] in biological and clinical research by MALDI MS imaging

In recent years the analysis in mass spectrometry (MS) [corrected] imaging has been expanded to detect a wide variety of low molecular weight compounds (LMWC), including exogenous and endogenous compounds. The high sensitivity and selectivity of MS imaging combined with visualization of molecular spatial distribution in tissues, makes it a valuable [corrected] platform in targeted drug and untargeted metabolomic analysis [corrected] in biological and clinical research. Here, we review the current and potential applications of MALDI MS imaging in these areas. The aim of advancing MALDI MS imaging in the field of LMWC is to support clinical applications by understanding drug and drug-metabolite distribution, investigating toxicity and discovering [corrected] new biomarkers.

Autoradiography techniques and quantification of drug distribution

The use of radiolabeled drug compounds offers the most efficient way to quantify the amount of drug and/or drug-derived metabolites in biological samples. Autoradiography is a technique using X- ray film, phosphor imaging plates, beta imaging systems, or photo-nuclear emulsion to visualize molecules or fragments of molecules that have been radioactively labeled, and it has been used to quantify and localize drugs in tissues and cells for decades. Quantitative whole-body autoradiography or autoradioluminography (QWBA) using phosphor imaging technology has revolutionized the conduct of drug distribution studies by providing high resolution images of the spatial distribution and matching tissue concentrations of drug-related radioactivity throughout the body of laboratory animals. This provides tissue-specific pharmacokinetic (PK) compartmental analysis which has been useful in toxicology, pharmacology, and drug disposition/patterns, and to predict human exposure to drugs and metabolites, and also radioactivity, when a human radiolabeled drug study is necessary. Microautoradiography (MARG) is another autoradiographic technique that qualitatively resolves the localization of radiolabeled compounds to the cellular level in a histological preparation. There are several examples in the literature of investigators attempting to obtain drug concentration data from MARG samples; however, there are technical issues which make that problematic. These issues will be discussed. This review will present a synopsis of both techniques and examples of how they have been used for drug research in recent years.

Mass spectrometry imaging: a new vision in differentiating Schistosoma mansoni strains

Schistosomiasis is a neglected disease with large geographic distribution worldwide. Among the several different species of this parasite, S. mansoni is the most common and relevant one; its pathogenesis is also known to vary according to the worms' strain. High parasitical virulence is directly related to granulomatous reactions in the host's liver, and might be influenced by one or more molecules involved in a specific metabolic pathway. Therefore, better understanding the metabolic profile of these organisms is necessary, especially for an increased potential of unraveling strain virulence mechanisms and resistance to existing treatments. In this report, MALDI-MSI and the metabolomic platform were employed to characterize and differentiate two Brazilian S. mansoni strains: males and females from Belo Horizonte (BH) and from Sergipe (SE). By performing direct analysis, it is possible to distinguish the sex of adult worms, as well as identify the spatial distribution of chemical markers. Phospholipids, diacylglycerols and triacylglycerols were located in specific structures of the worms' bodies, such as tegument, suckers, reproductive and digestive systems. Lipid profiles were found to be different both between strains and males or females, giving specific metabolic fingerprints for each group. This indicates that biochemical characterization of adult S. mansoni may help narrowing-down the investigation of new therapeutic targets according to worm composition, molecule distribution and, therefore, aggressiveness of disease.

Cosmetic Analysis Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI)

A new "omic" platform-Cosmetomics-that proves to be extremely simple and effective in terms of sample preparation and readiness for data acquisition/interpretation is presented. This novel approach employing Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) for cosmetic analysis has proven to readily identify and quantify compounds of interest. It also allows full control of all the production phases, as well as of the final product, by integration of both analytical and statistical data. This work has focused on products of daily use, namely nail polish, lipsticks and eyeliners of multiple brands sold in the worldwide market.

MALDI imaging mass spectrometry: bridging biology and chemistry in drug development

Our understanding of drug tissue distribution impacts a number of areas in drug development, including: pharmacology, pharmacokinetics, safety, drug-drug interactions, transport and metabolism. Despite their extensive use, autoradiography and tissue homogenate LC-MS analysis have limitations in providing a comprehensive assessment of tissue distributions. In the case of autoradiography, it is the inability to distinguish between parent drug and drug metabolites. In LC-MS analysis of tissue homogenate, all tissue localization information is lost. The emerging technique of MALDI imaging mass spectrometry has the capability to distinguish between parent and metabolites while maintaining spatial distribution in tissues. In this article, we will review the MALDI imaging MS methodology as applied to drug development and provide examples highlighting the impact of this important technique in drug development.

Preclinical in vivo ADME studies in drug development: a critical review

INTRODUCTION

The last two decades have brought many fundamental changes to the drug development process. One such change is the importance of preclinical pharmacokinetics, which has become an essential part of early drug discovery. Furthermore, bioanalytical methods have become more sensitive and the identification and quantitation of metabolites can now be carried out on limited amount of biological material. There has also been a change in regulatory expectations, which are now particularly focused on the safety of human metabolites.

AREAS COVERED

The focus of this paper is on some 'traditional' in vivo ADME studies: excretion balance, metabolic profile and WBA in the toxicological species. These studies, performed with radiolabeled material, have a long history: and are a regular presence in submission dossiers. This paper reviews their value in the perspective of the contemporary drug development process.

EXPERT OPINION

These experiments may sometimes still be relevant to explain toxicological findings or for other special purposes but should not be considered required pieces of the registration dossiers. An appropriate investigation of samples coming from safety evaluation and human Phase I studies and the knowledge generated during the lead optimization phase provide, in most instances, all the DMPK information needed to take decisions in the drug development process.

Impact of various factors on radioactivity distribution in different DBS papers

Background: Dried blood spot (DBS) sampling could potentially become the preferred blood collection technique in toxicological and clinical studies. Autoradiography was performed to study compound distribution within a dbs under different conditions using five papers, 31ETF, Grade 226, 903®, FTA® and FTA® Elute. Results: The results showed an uneven distribution in all papers with common distribution patterns regardless of compounds: decreased concentrations along the edge, the volcano effect in the middle and the speckle pattern in the center. Treated papers were more readily influenced by environmental factors. Conclusion: Autoradiography enables visualization of a compound’s distribution and can guide bioanalytical assay development by allowing convenient evaluation of factors, such as choice of paper, spotting volume, punch size, punch location, temperature and humidity.

Autoradiography, MALDI-MS, and SIMS-MS imaging in pharmaceutical discovery and development

Whole-body autoradiography ((WBA) or quantitative WBA (QWBA)), microautoradiography (MARG), matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI), and secondary ion mass spectrometric imaging (SIMS-MSI) are high-resolution, molecular imaging techniques used to study the tissue distribution of radiolabeled and nonlabeled compounds in ex vivo, in situ biological samples. WBA, which is the imaging of the whole-body of lab animals, and/or their organ systems; and MARG, which provides information on the localization of radioactivity in histological preparations and at the cellular level, are used to support drug discovery and development efforts. These studies enable the conduct of human radiolabeled metabolite studies and have provided pharmaceutical scientists with a high resolution and quantitative method of accessing tissue distribution. MALDI-MSI is a mass spectrometric imaging technique capable of label-free and simultaneous determination of the identity and distribution of xenobiotics and their metabolites as well as endogenous substances in biological samples. This makes it an interesting extension to WBA and MARG, eliminating the need for radiochemistry and providing molecular specific information. SIMS-MSI offers a complementary method to MALDI-MSI for the acquisition of images with higher spatial resolution directly from biological specimens. Although traditionally used for the analysis of surface films and polymers, SIMS has been used successfully for the study of biological tissues and cell types, thus enabling the acquisition of images at submicrometer resolution with a minimum of samples preparation.

Applications of MALDI-MSI to pharmaceutical research

MALDI-MSI has been demonstrated to be a suitable technique in pharmaceutical research for providing information of the distribution of low molecular weight compounds such as drugs and their metabolites within whole-body tissue sections. Important ADME information can be determined by MALDI-MSI analysis of the distribution of drugs and metabolites in whole-body tissue sections taken from animals killed at a range of time points postdose. In this example we applied MALDI-MSI to the localization of a compound and its primary metabolite in whole-body mouse sections.

Biomarkers and imaging: physics and chemistry for noninvasive analyses

The era of ‘modern medicine’ has changed its name to ‘molecular medicine’, and reflects a new age based on personalized medicine utilizing molecular biomarkers in the diagnosis, staging and monitoring of therapy. Alzheimer’s disease has a classical biomarker determined at autopsy with the histologic staining of amyloid accumulation in the brain. Today we can diagnose Alzheimer’s disease using the same classical pathologic biomarker, but now using a noninvasive imaging probe to image the amyloid deposition in a patient and potentially provide treatment strategies and measure their effectiveness. Molecular medicine is the exploitation of biomarkers to detect disease before overt expression of pathology. Physicians can now find, fight and follow disease using imaging, and the need for other disease biomarkers is in high demand. This review will discuss the innovative physical and molecular biomarker probes now being developed for imaging systems and we will introduce the concepts needed for validation and regulatory acceptance of surrogate biomarkers in the detection and treatment of disease.