Profluent is the frontier AI lab for biology. Profluent builds powerful foundation models for all of life's molecules, unlocking solutions that transform medicine, agriculture, and beyond. Founded in 2022 and headquartered in Emeryville, CA, Profluent is backed by leading investors including Altimeter Capital, Bezos Expeditions, Spark Capital, Insight Partners, Air Street Capital, AIX Ventures, and Convergent Ventures and has raised over $150M to date. We are seeking a talented, self-motivated, and highly resourceful Scientist I / Scientist II to serve as a foundational scientist in establishing our next-generation Targeted Lipid Nanoparticle (tLNP) platform. This role is central to our strategy of achieving extrahepatic tissue tropism for next-generation genetic medicines. In this position, you will own the end-to-end design, formulation, bioconjugation, and physicochemical characterization of novel tLNPs. You will establish our internal in vitro cell culture and assay pipeline to validate targeting and cellular uptake, while serving as the primary technical interface for in vivo studies. This is a high-visibility, high-impact role ideal for an agile scientist with strong drug delivery foundations who thrives in an entrepreneurial environment. Responsibilities - Design and execute tLNP formulations encapsulating nucleic acid payloads (e.g., mRNA, sgRNA), systematically altering lipid ratios, ionizable lipid structures, and helper components to drive extrahepatic tissue tropism. - Perform hands-on surface modifications and bioconjugation chemistries (e.g., maleimide-thiol, click chemistry, enzymatic tags) to attach targeting moieties (antibodies, VHHs/nanobodies, peptides) to LNP surfaces. - Perform routine and advanced LNP analytics, including particle size/polydispersity (e.g., dynamic light scattering), zeta potential and encapsulation efficiency (e.g., RiboGreen assays) and Degree of Labeling (DoL) for conjugated ligands. - Establish and maintain mammalian cell culture models to support platform screening needs. Develop, optimize, and execute robust in vitro assays (using Flow Cytometry/FACS, plate readers, and fluorescence/luminescence imaging) to evaluate target binding, receptor-mediated cellular uptake, endosomal escape, and functional cargo translation. - Design robust in vivo biodistribution, pharmacokinetic (PK), and organ-targeting studies to evaluate tLNP performance. Analyze, interpret datasets to establish clear structure-activity relationships (SAR) for the next round of formulation design. - Maintain detailed Electronic Lab Notebook (ELN) records, author technical reports, generate patent disclosure data, and present findings to cross-functional scientific leadership. Qualifications - Scientist I: Ph.D. in Biomedical Engineering, Chemical Engineering, Pharmaceutical Sciences, or a related field with 0–2 years of relevant experience. Scientist II: Ph.D. in the same disciplines with 2–4 years of relevant experience. - Hands-on experience with LNP assembly platforms (microfluidic/NanoAssemblr, T-junction, or ethanol injection) and surface bioconjugation techniques to functionalize nanoparticles with targeting moieties. - Demonstrated understanding and experience in shifting nanoparticle biodistribution/tropism through lipid compositional tweaking, molar ratio modification, or structural lipid alteration. - Hands-on proficiency in mammalian cell culture and running quantitative cell-based assays (Flow Cytometry/FACS, reporter assays, ELISAs). - Understanding of systemic nanoparticle distribution, protein corona formation, vascular barriers, and in vivo study design principles. (Hands-on animal dosing or ex vivo tissue processing experience is not required). - Entrepreneurial drive and organizational skills suited for building assays, protocols, and workflows in an early-stage, growing R&D environment. Preferences (Nice to Have) - Experience with automated or high-throughput liquid-handling platforms for formulation screening. - Practical knowledge of Design of Experiments (DoE) software (e.g., JMP) for systematic library screening. - Experience with advanced nanoparticle characterization techniques (e.g. HPLC-SEC, UPLC-CAD). What We Offer - High-growth opportunity with meaningful impact on the future of protein design - Competitive compensation package with equity participation - 401(k) with a strong employer match - Comprehensive benefits including health/dental/vision insurance - Generous PTO policy and commitment to work-life balance - Professional development opportunities in a cutting-edge field at the intersection of AI and biology Profluent Bio, Inc is an equal opportunity employer promoting diversity and inclusion in the workspace. We do not discriminate on the basis of race, color, religion, marital status, age, national origin, ancestry, physical or mental disability, medical conditions, veteran status, sexual orientation, gender (including gender identity and gender expression), sex (which includes pregnancy, childbirth, and breastfeeding), genetic information, taking or requesting statutorily protected leave, or any other basis protected by law. Work Authorization Requirement Applicants must have ongoing work authorization in the United States that does not require employer sponsorship. Sponsorship will not be provided now or at any time in the future for this position. Employment Eligibility Verification Legal authorization to work in the United States is required. In compliance with federal law, all persons hired must verify their identity and work eligibility and complete the required employment verification form upon hire. Hiring Salary Range $132,000 — $160,000 USD NOTICE TO STAFFING AND SEARCH FIRMS: Profluent does not accept unsolicited candidate submissions. We ask that agencies refrain from sending resumes to our careers inbox, hiring managers, or any Profluent employee. Any resume submitted without a signed agreement and an active search request from our Talent team will be treated as the property of Profluent, and no placement fee will be owed.