Antimicrobial resistance (AMR) constitutes a defining crisis in contemporary infectious disease medicine. The review highlights the escalating resistance among Gram-negative organisms, specifically naming carbapenem-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae as prominent threats. These pathogens are increasingly refractory to standard treatments and represent an urgent need for alternative therapeutic strategies.
Traditional antibiotic approaches are frequently ineffective against problematic Gram-negative bacteria because of structural and functional defenses. The presence of multiple envelope layers and active efflux pumps limits antibiotic penetration and retention. In addition, biofilm production further protects bacterial communities from antimicrobial exposure.
The review also notes that bacteriolytic therapies—agents that lyse bacteria—can paradoxically exacerbate host injury. Lysis of Gram-negative bacteria releases endotoxin (lipopolysaccharide, LPS) systemically, which can provoke deleterious immunopathology rather than resolving infection.
Host-defense peptides are presented as a promising alternative modality because they combine several potentially advantageous effects in a single therapeutic: direct bactericidal activity, LPS neutralization, and modulation of innate immune responses. By targeting both microbes and the host immune environment, these peptides could address weaknesses of classical antibiotics while reducing the risk of endotoxin-driven pathology associated with bacteriolytic approaches.
Despite their multifaceted actions, translation of host-defense peptides into clinical practice has been limited. Key barriers identified include low in vivo stability, high binding to serum proteins that reduces bioavailable peptide, and a narrow therapeutic index that constrains dosing. These pharmacological and safety challenges reduce clinical utility and necessitate strategies to enhance peptide half-life and selectivity.
The review discusses the use of biomaterial platforms to overcome peptide limitations. Incorporation of peptides into biomaterials can increase efficacy by reducing peptide clearance and protecting peptides from degradation. Beyond pharmacokinetic benefits, biomaterials can be engineered to optimize the immunological milieu in which peptides act, potentially enhancing desired immune-modulatory effects while limiting toxicity.
Examples of biomaterial-directed approaches discussed include design choices that influence peptide presentation, retention, and local concentration. The central premise is that pairing peptide design with materials engineering can deliver peptides more effectively to sites of infection and modulate host responses for better outcomes.
Several biomaterial characteristics can affect innate immune cells and downstream signaling pathways. The review highlights three specific properties:
Surface chemistry: chemical groups on material surfaces affect protein adsorption, cell interactions, and immune recognition.
Mechanical stiffness: substrate rigidity can influence macrophage phenotype and function, thereby altering the local immune response to infection.
Protein corona: the layer of host proteins that adsorb onto materials in biological fluids modifies how immune cells perceive and respond to the material–peptide construct.
Together, these factors can drive macrophage polarization and signaling cascades that either support microbial clearance and tissue repair or promote inflammation and pathology. Engineering these properties offers a route to steer immune responses in favor of therapeutic goals.
The authors identify a significant limitation in the preclinical literature: continued reliance on standard microbiological and cytotoxicity readouts, such as minimum inhibitory concentration (MIC) and hemolysis assays. These measures assess direct antimicrobial potency and erythrocyte toxicity but do not capture the host-directed, immunomodulatory effects that are central to peptide–biomaterial approaches.
Because many host-directed benefits relate to immune modulation rather than direct killing alone, the authors argue that MIC and hemolysis are insufficient endpoints. They also call for more clinically relevant animal models that reflect complex host–pathogen interactions and for endpoints that quantify immune outcomes and host safety in context.
For the field to progress, the review recommends development of new experimental endpoints that measure host-directed effects, use of animal models with higher clinical relevance, and deeper integration of peptide design principles into biomaterials engineering workflows. True translational advancement will require shifting toward assays and models that reflect the combined antimicrobial and immunomodulatory functions of host-defense peptides within engineered biomaterial systems.
Publication details: this is a review article (Biomater Sci. 2026 Aug 25;14(17):4399-4417) by Muhammad Adil and colleagues, indexed in PubMed (PMID 42412003, DOI 10.1039/d6bm00666c). The affiliations listed include the CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety at the National Centre for Nanoscience and Technology, the University of Chinese Academy of Sciences, and the School of Material Science and Engineering at Beijing Institute of Technology.
Note: The source text is the PubMed record and abstract for the review; detailed experimental data, specific biomaterial formulations, and quantitative outcomes were not reported in the abstract and therefore are not described here.