Functional pharmaceutical excipient from cellulose to enhance the effectiveness of antibiotics and inhibit drug resistance

Abstract

Antibiotic-resistance crisis poses a severe threat to global public health and healthcare sustainability. Herein, we developed a functional pharmaceutical excipient, deoxy-cationic cellulose C-TBuP_0.25 derived from natural cellulose. It exhibits excellent hemocompatibility, with a red blood cell hemolysis rate of less than 1.0% at a high concentration of 1000 μg/mL, and white blood cell and platelet survival rates as high as 99.1% and 99.9%, respectively. C-TBuP_0.25 enhances the permeability of both bacterial inner and outer membranes, dissipates the transmembrane proton gradient, inhibits bacterial efflux pump activity, and induces the accumulation of reactive oxygen species, thereby significantly increasing the antibacterial activity of antibiotics. Even at sub-inhibitory concentrations, C-TBuP_0.25 can fully restore the sensitivity of multidrugresistant Escherichia coli and Acinetobacter baumannii to previously ineffective antibiotics such as rifampicin. Continuous passaging and transcriptomics (RNA-seq) analyses indicate that combining C-TBuP_0.25 with antibiotics activates the BasR/S stress pathway, induces lethal oxidative stress, and completely disrupts the ribosomal translational compensation mechanism, thereby preventing the emergence of resistance. In mouse models of skin infection and systemic infection, the combination therapy demonstrates excellent bacteria-clearing ability. Given that cellulose materials are commonly used as pharmaceutical excipients, C-TBuP_0.25 holds promise as an antibiotic adjunct to combat drug-resistant bacteria.

Introduction

Bacterial infections pose a serious threat to public health worldwide1–3. Since the 20th century, the discovery and widespread use of antibiotics have provided humanity with a revolutionary advantage in combating bacteria, leading to tremendous clinical success4. Antibiotics like penicillin and amoxicillin exert their bactericidal effect by inhibiting bacterial cell wall synthesis. They are effective against a range of Grampositive bacteria (e.g., streptococci, staphylococci) as well as certain Gram-negative pathogens (e.g., Escherichia coli (E. coli), Haemophilus influenzae). Antibiotics has played a crucial role in substantially decreasing mortality due to bacterial infections in both humans and animals5,6.

However, their over use has led to a rapid increase in antimicrobial resistance7. Bacteria counteract antibiotics through various strategies, including reducing outer membrane permeability, enhancing efflux pump activity, undergoing genetic mutations, producing inactivating enzymes, and forming biofilms8,9. Meanwhile, the development of new antibiotics is time consuming and costly, lagging far behind the pace of bacterial evolution4. Currently, drug-resistant bacteria, particularly “ESKAPE” bacteria (including Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) 10–13, have become a serious global public health challenge.

The world health organization (WHO) predicts that, in the absence of effective interventions, infections caused by drug-resistant bacteria could result in approximately 10 million deaths annually by 2050, surpassing cancer as the leading cause of death worldwide14. Over the past two decades, the search for treatments against multidrug resistant pathogens has garnered widespread attention. Combination therapy represents an effective strategy to combat and prevent bacterial resistance. One approach involves the concurrent use of two or more antibiotics, which can prolong the clinical utility of these drugs, reduce side effects, and delay the emergence of resistance. Another approach combines antibiotics with nonantibiotic agents that target specific resistance mechanisms, therefore restoring the activity of otherwise ineffective antibiotics against multidrug-resistant strains8,15.

For example, clinically approved combinations of β-lactams and β-lactamase inhibitors, as well as various similar strategies currently under clinical trials, underscore the promise of this approach16,17. These non-antibiotic agents, which exhibit low or no antimicrobial activity, are known as “antibiotic adjuvants”. They restore antibiotic activity by either actively or passively targeting bacteria, or by disrupting bacterial functions18. Developed antibiotic adjuvants include enzyme inhibitors19, active efflux pump inhibitors20, teichoic acid biosynthesis inhibitors21, host-derived antimicrobial peptides22, chitosan-modified oligolysine antimicrobial peptides23, and polysulfide and glucan thiol derivatives24, and so on.

However, the current synthesis and/or purification processes for these antibiotic adjuvants are complex and uneconomical, limiting their application. Cellulose and its derivatives are medicinal excipients approved by the U.S. food and drug administration (FDA). They are essential raw materials in pharmaceutical manufacturing25. For example, microcrystalline cellulose serves as a binder in drug formulation, facilitating drug administration26. Hydroxypropylmethylcellulose (Hypromellose) and hydroxypropyl cellulose (HPC) function as coating materials and sustained-release agents to regulate drug release rates27.

Hypromellose acetate succinate and hypromellose phthalate are used as coating materials to control the site of drug release28. By regulating the chemical structure and microscopic morphology of cellulose materials, it is possible to develop functional pharmaceutical excipients with the potential to enhance the efficacy of antibiotics and inhibit the emergence of drug-resistant bacteria. In this work, we modified the chemical structure of cellulose materials via a deoxygenation process to produce deoxy-cationic cellulose C-TBuP0.25 with excellent biocompatibility. It enhances both inner and outer membrane permeability, dissipates the transmembrane proton gradient, inhibits efflux pump activity, induces reactive oxygen species (ROS) accumulation, and disrupts ribosomal translation compensation mechanism. As a functional pharmaceutical excipient, C-TBuP0.25 significantly enhances the antibacterial effects of various antibiotics and suppresses the development of drug resistance (Figure 1).

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Materials

Pyridine (Py, anhydrous), p-toluenesulfonyl chloride (TsCl), dimethyl sulfoxide(DMSO, anhydrous), N,N-dimethylbenzylamine (DMBenA), benzylimidazole(BenIm), ethanolamine (EtOHA), N,N-dimethylhexanamine (DMHeA),tributylphosphine (TBuP), paraformaldehyde, rifampin (RIF), levofloxacin (LEV),tobramycin (TOB), tetracycline (TET), meropenem (MER), sodium edetate, Triton X-100, glutaraldehyde, isopentyl acetate, agarose, PBS buffer, sodium chloride, N-phenyl-α-naphthylamine (NPN), propidium iodide (PI), 3,3′-di-n-hexyl-oxacarbocyanine iodide (DiSC₃(5)), Ethidium bromide (EB), 2′,7′-dichlorofluoresceindiacetate (DCFH-DA), 4′,6′-diamino-2-phenylindole (DAPI), fluoresceinisothiocyanate isomer I (FITC), and ethanol were purchased from Beijing InnoCareTechnology Co., Ltd. Microcrystalline cellulose (MCC, DP = 220) was purchased from Beijing Fengli Jingqiu Pharmaceutical Co., Ltd. 1-Allyl-3-methylimidazolium chloride(AmimCl) was purchased from Shandong Zhongke Henglian Bio-based Materials Co.,Ltd. Deuterated trifluoroacetic acid and deuterated dimethyl sulfoxide (containing 0.03%tetramethylsilane) were purchased from An’nai Ji Pharmaceutical Chemistry Co., Ltd.Plate Count Agar (PCA) and MH broth were purchased from Changde Beckman Biotechnology Co., Ltd. Red blood cells, E. coli, and A. baumannii strains were provided by the Fifth Medical Center of the Chinese PLA General Hospital.Synthesis of C-TsMCC (1.62 g).

Functional pharmaceutical excipient from cellulose to enhance the effectiveness of antibiotics and inhibit drug resistance, Linxi Chen, Xi Wang, Hailong Zhuo, Chunchun Yin, Qun Luo, Jun Zhang and Jinming Zhang, Online publication date: 8 Sep 2026, https://doi.org/10.31635/ccschem.026.202608343

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