Mitch A. Garcia

Capture and Stimulated Release of Circulating Tumor Cells on Polymer‐Grafted Silicon Nanostructures

A platform for capture and release of circulating tumor cells is demonstrated by utilizing polymer grafted silicon nanowires. In this platform, integration of ligand-receptor recognition, nanostructure amplification, and thermal responsive polymers enables a highly efficient and selective capture of cancer cells. Subsequently, these captured cells are released upon a physical stimulation with outstanding cell viability.

Specific Capture and Release of Circulating Tumor Cells Using Aptamer‐Modified Nanosubstrates

Circulating tumor cells (CTCs)[1] are cancer cells that have propagated from tumors, spreading into the bloodstream as the cellular origin of fatal metastasis. Besides conventional diagnostic approaches (e.g., tumor biopsy, anatomical/molecular imaging and serum marker detection), detecting CTCs in peripheral blood is of prognostic value in different types of solid tumors, especially for predicting patient survival. The fact is that CTC detection have been technically challenging because of the extremely low abundance (a few to hundreds per mL) of CTCs among a high number (109 cells mL-1) of hematologic cells.[2] Over the past decade, a diversity of diagnostic technologies has been demonstrated for CTC detection using different working mechanisms. The current FDA-cleared CellSearch™ Assay is based on immunomagnetic separation of CTCs. Due to its unsatisfactory efficiency and high cost, researchers have been exploiting new technologies,[3] e.g., flow cytometry, size-based filtration systems and microfluidic devices that may offer improved sensitivity and reduced cost for CTC detection. In addition to the prognostic utility of CTC-based diagnostics, it is conceivable that the molecular signatures and functional readouts derived from CTCs will shed much valuable insight into tumor biology during the critical window where therapeutic intervention could make a significant difference.

On‐Demand Drug Release System for In Vivo Cancer Treatment through Self‐Assembled Magnetic Nanoparticles

The intrinsic nature of small-molecule chemotherapeutics, including i) limited aqueous solubility, ii) systemic toxicity due to non-specific whole-body distribution, and iii) potential development of drug resistance after initial administration, compromises their treatment efficacy.[1] Recently, nanoparticle (NP)-based drug delivery systems have been considered as promising alternatives to overcome some of these limitations and begin to resolve obstacles in the disease management in clinical oncology.[2] The intraparticular space of a NP vector can be employed to package drug payloads without constrain associated with their solubility. Further, NP vectors exhibit enhanced permeability and retention (EPR) effects[3] that facilitate the differential uptake, leading to preferential spatio-distribution in tumor.[4] However, conventional NP drug delivery systems tend to passively release drug payloads, limiting the ability to release an effective drug concentration at a desired time window. Therefore, there is a need to develop next-generation NP drug delivery system such as a stimuli-responsive drug release system with a goal of achieving spatio-temporal control, by which an acute level of drug concentration can be delivered at the time point the NP vectors reach maximum tumor accumulation.[5] By doing so, it is expected to dramatically improve therapeutic effects in tumor and effectively reduce systematic toxicity at a minute drug dosage.[6]

Polymer Nanofiber‐Embedded Microchips for Detection, Isolation, and Molecular Analysis of Single Circulating Melanoma Cells

Circulating tumor cells (CTCs)[1] are cancer cells shed from either the primary tumors or metastatic sites. The presence and number of CTCs in peripheral blood can provide clinically significant data on prognosis and therapeutic response patterns, respectively[2]. Thus, as with traditional invasive tumor biopsies that enable gold-standard pathological analysis, CTCs can be regarded as “liquid biopsies” of the tumor, which enable repeated and relatively non-invasive characterization of tumor evolution, especially important during therapeutic interventions. Currently, FDA-cleared CellSearch™ Assay is costly and inefficient in capturing CTCs, and the enriched CTCs are typically contaminated with a large number of white blood cells (WBCs). As a result, the diagnostic value of CTCs has been underutilized. Over the past decade, a diversity of CTC detection technologies[2d, 3] have been developed to overcome the challenges encountered by the immunomagnetic separation-based CellSearch™ Assay.

High‐Purity Prostate Circulating Tumor Cell Isolation by a Polymer Nanofiber‐Embedded Microchip for Whole Exome Sequencing

Handpick single cancer cells: a modified NanoVelcro Chip is coupled with ArcturusXT laser capture microdissection (LCM) technology to enable the detection and isolation of single circulating tumor cells (CTCs) from patients with prostate cancer (PC). This new approach paves the way for conducting next-generation sequencing (NGS) on single CTCs.

A rapid pathway toward a superb gene delivery system: programming structural and functional diversity into a supramolecular nanoparticle library.

Nanoparticles are regarded as promising transfection reagents for effective and safe delivery of nucleic acids into a specific type of cells or tissues providing an alternative manipulation/therapy strategy to viral gene delivery. However, the current process of searching novel delivery materials is limited due to conventional low-throughput and time-consuming multistep synthetic approaches. Additionally, conventional approaches are frequently accompanied with unpredictability and continual optimization refinements, impeding flexible generation of material diversity creating a major obstacle to achieving high transfection performance. Here we have demonstrated a rapid developmental pathway toward highly efficient gene delivery systems by leveraging the powers of a supramolecular synthetic approach and a custom-designed digital microreactor. Using the digital microreactor, broad structural/functional diversity can be programmed into a library of DNA-encapsulated supramolecular nanoparticles (DNA⊂SNPs) by systematically altering the mixing ratios of molecular building blocks and a DNA plasmid. In vitro transfection studies with DNA⊂SNPs library identified the DNA⊂SNPs with the highest gene transfection efficiency, which can be attributed to cooperative effects of structures and surface chemistry of DNA⊂SNPs. We envision such a rapid developmental pathway can be adopted for generating nanoparticle-based vectors for delivery of a variety of loads.

NanoVelcro Chip for CTC enumeration in prostate cancer patients

Circulating tumor cells (CTCs) are one of the most crucial topics in rare cell biology and have become the focus of a significant and emerging area of cancer research. While CTC enumeration is a valid biomarker in prostate cancer, the current FDA-approved CTC technology is unable to detect CTCs in a large portion of late stage prostate cancer patients. Here we introduce the NanoVelcro CTC Chip, a device composed of a patterned silicon nanowire substrate (SiNW) and an overlaid polydimethylsiloxane (PDMS) chaotic mixer. Validated by two institutions participating in the study, the NanoVelcro Chip assay exhibits very consistent efficiency in CTC-capture from patient samples. The utilized protocol can be easily replicated at different facilities. We demonstrate the clinical utility of the NanoVelcro Chip by performing serial enumerations of CTCs in prostate cancer patients after undergoing systemic therapy. Changes in CTC numbers after 4-10 weeks of therapy were compared with their clinical responses. We observed a statistically significant reduction in CTCs counts in the clinical responders. We performed long-term follow up with serial CTC collection and enumeration in one patient observing variations in counts correlating with treatment response. This study demonstrates the consistency of the NanoVelcro Chip assay over time for CTC enumeration and also shows that continuous monitoring of CTC numbers can be employed to follow responses to different treatments and monitor disease progression.

Programming thermoresponsiveness of NanoVelcro substrates enables effective purification of circulating tumor cells in lung cancer patients.

Unlike tumor biopsies that can be constrained by problems such as sampling bias, circulating tumor cells (CTCs) are regarded as the “liquid biopsy” of the tumor, providing convenient access to all disease sites, including primary tumor and fatal metastases. Although enumerating CTCs is of prognostic significance in solid tumors, it is conceivable that performing molecular and functional analyses on CTCs will reveal much significant insight into tumor biology to guide proper therapeutic intervention. We developed the Thermoresponsive NanoVelcro CTC purification system that can be digitally programmed to achieve an optimal performance for purifying CTCs from non-small cell lung cancer (NSCLC) patients. The performance of this unique CTC purification system was optimized by systematically modulating surface chemistry, flow rates, and heating/cooling cycles. By applying a physiologically endurable stimulation (i.e., temperature between 4 and 37 °C), the mild operational parameters allow minimum disruption to CTCs’ viability and molecular integrity. Subsequently, we were able to successfully demonstrate culture expansion and mutational analysis of the CTCs purified by this CTC purification system. Most excitingly, we adopted the combined use of the Thermoresponsive NanoVelcro system with downstream mutational analysis to monitor the disease evolution of an index NSCLC patient, highlighting its translational value in managing NSCLC.

The Therapeutic Efficacy of Camptothecin-Encapsulated Supramolecular Nanoparticles

Nanomaterials have been increasingly employed as drug(s)-incorporated vectors for drug delivery due to their potential of maximizing therapeutic efficacy while minimizing systemic side effects. However, there have been two main challenges for these vectors: (i) the existing synthetic approaches are cumbersome and incapable of achieving precise control of their structural properties, which will affect their biodistribution and therapeutic efficacies, and (ii) lack of an early checkpoint to quickly predict which drug(s)-incorporated vectors exhibit optimal therapeutic outcomes. In this work, we utilized a new rational developmental approach to rapidly screen nanoparticle (NP)-based cancer therapeutic agents containing a built-in companion diagnostic utility for optimal therapeutic efficacy. The approach leverages the advantages of a self-assembly synthetic method for preparation of two different sizes of drug-incorporated supramolecular nanoparticles (SNPs), and a positron emission tomography (PET) imaging-based biodistribution study to quickly evaluate the accumulation of SNPs at a tumor site in vivo and select the favorable SNPs for in vivo therapeutic study. Finally, the enhanced in vivo anti-tumor efficacy of the selected SNPs was validated by tumor reduction/inhibition studies. We foresee our rational developmental approach providing a general strategy in the search of optimal therapeutic agents among the diversity of NP-based therapeutic agents.

Subclassification of prostate cancer circulating tumor cells by nuclear size reveals very small nuclear circulating tumor cells in patients with visceral metastases.

Although enumeration of circulating tumor cells (CTCs) has shown some clinical value, the pool of CTCs contains a mixture of cells that contains additional information that can be extracted. The authors subclassified CTCs by shape features focusing on nuclear size and related this with clinical information.