Ferroptosis, an iron-dependent, non-apoptotic cell death program, is involved in various degenerative diseases and represents a targetable vulnerability in certain cancers 1 . The ferroptosissusceptible cell state can either preexist in cells arising from certain lineages or be acquired during cell-state transitions 2-5 . Precisely how ferroptosis susceptibility is dynamically regulated remains poorly understood. Using genome-wide CRISPR/Cas9 suppressor screens, we identify the peroxisome organelle as a critical contributor to ferroptosis sensitivity in human renal and ovarian carcinoma cells. By lipidomic profiling, we show that peroxisomes contribute to ferroptosis through the synthesis of polyunsaturated ether phospholipids (PUFA-ePLs), an understudied lipid *

Nanoparticle surface chemistry is a fundamental engineering parameter that governs tumor-targeting activity. Electrostatic assembly generates controlled polyelectrolyte complexes through the process of adsorption and charge overcompensation utilizing synthetic polyions and natural biomacromolecules; it can yield films with distinctive hydration, charge, and presentation of functional groups. Here, we used electrostatic layer-by-layer (LbL) assembly to screen 10 different surface chemistries for their ability to preferentially target human ovarian cancer in vitro. Our screen identified that poly-Laspartate, poly-L-glutamate, and hyaluronate-coated LbL nanoparticles have striking specificity for ovarian cancer, while sulfated poly(β-cyclodextrin) nanoparticles target noncancerous stromal cells. We validated top candidates for tumor-homing ability with a murine model of metastatic disease and with patient-derived ovarian cancer spheroids. Nanoparticle surface chemistry also influenced subcellular trafficking, indicating strategies to target the cell membrane, caveolae, and perinuclear vesicles. Our results confirm LbL is a powerful tool to systematically engineer nanoparticles and achieve specific targeting.

A shortage of available organ donors has created a need for engineered tissues. In this context, polymer-based hydrogels that break down inside the body are often used as constructs for growth factors and cells. Herein, we report imine cross-linked gels where degradation is controllable by the introduction of mixed imine cross-links. Specifically, hydrazide-functionalized poly(ethylene glycol) (PEG) reacts with aldehyde-functionalized PEG (PEG-CHO) to form hydrazone linked hydrogels that degrade quickly in media. The time to degradation can be controlled by changing the structure of the hydrazide group or by introducing hydroxylamines to form non-reversible oxime linkages. Hydrogels containing adipohydrazide-functionalized PEG (PEG-ADH) and PEG-CHO were found to degrade more rapidly than gels formed from carbodihydrazide-functionalized PEG (PEG-CDH). Incorporating oxime linkages via aminooxy-functionalized PEG (PEG-AO) into the hydrazone cross-linked gels further stabilized the hydrogels. This imine crosslinking approach should be useful for modulating the degradation characteristics of 3D cell culture supports for controlled cell release.

Layer-by-layer (LbL) nanoparticles offer great potential to the field of drug delivery, where these nanocomposites have been studied for their ability to deliver chemotherapeutic agents, small molecule inhibitors, and nucleic acids. Most exciting is their ability to encapsulate multiple functional elements, which allow nanocarriers to deliver complex combination therapies with staged release. However, relative to planar LbL constructs, colloidal LbL systems have not undergone extensive systematic studies that outline critical synthetic solution conditions needed for robust and efficient assembly. The multistaged process of adsorbing a series of materials onto a nanoscopic template is inherently complex, and facilitating the self-assembly of these materials depends on identifying proper solution conditions for each synthetic step and adsorbed material. Here, we focus on addressing some of the fundamental questions that must be answered in order to obtain a reliable and robust synthesis of nucleic acid-containing LbL liposomes. This includes a study of solution conditions, such as pH, ionic strength, salt composition, and valency, and their impact on the preparation of LbL nanoparticles. Our results provide insight into the selection of solution conditions to control the degree of ionization and the electrostatic screening length to suit the adsorption of nucleic acids and synthetic polypeptides. The optimization of these parameters led to a roughly 8-fold improvement in nucleic acid loading in LbL liposomes, indicating the *

To accelerate the translation of cancer nanomedicine, we used an integrated genomic approach to improve our understanding of the cellular processes that govern nanoparticle trafficking. We developed a massively parallel screen that leverages barcoded, pooled cancer cell lines annotated with multiomic data to investigate cell association patterns across a nanoparticle library spanning a range of formulations with clinical potential. We identified both materials properties and cell-intrinsic features that mediate nanoparticle-cell association. Using machine learning algorithms, we constructed genomic nanoparticle trafficking networks and identified nanoparticle-specific biomarkers. We validated one such biomarker: gene expression of SLC46A3 , which inversely predicts lipid-based nanoparticle uptake in vitro and in vivo. Our work establishes the power of integrated screens for nanoparticle delivery and enables the identification and utilization of biomarkers to rationally design nanoformulations.