Gelatin Hydrogel Salbutamol Study Retracted Over Overlapping Microscopy Images

A study that promised a new way to deliver the asthma drug salbutamol sulphate through gelatin-based swellable hydrogels has been struck from the scientific record. The Editors-in-Chief of Polymer Bulletin, a Springer Nature journal dedicated to polymer science and engineering, have formally retracted the paper, which originally appeared online on 19 May 2021 and was published in the journal’s volume 79 under the title “Designing gelatin-based swellable hydrogels system for controlled delivery of salbutamol sulphate: characterization and toxicity evaluation.” The retraction notice, published as volume 83, article number 628, states bluntly that the editors no longer have confidence in the presented data. The decision closes a chapter on a piece of research that had been cited as an example of how natural polymers might be engineered into drug delivery vehicles for water-soluble bronchodilators.

The retraction centers on problems with the paper’s microscopy images, which formed the visual backbone of its toxicity evaluation. According to the notice, concerns were raised after publication regarding image overlap in Figure 7f between the Control and Unloaded hydrogel groups. In practical terms, this means that two images that were supposed to show different experimental conditions—one representing untreated control tissue and the other tissue exposed to the hydrogel formulation without drug—appeared to contain the same or substantially identical pictorial content. For readers assessing whether a biomaterial is safe, such duplication is not a cosmetic flaw. It undermines the very comparison that the toxicity section was designed to establish, because the reader cannot know what the true untreated baseline looked like or whether the loaded and unloaded formulations produced distinct histological effects.

The problems did not stop within the retracted paper itself. The Editors-in-Chief also found that the Figure 7c Control image appeared to overlap with an image labeled Figure 11 Lung I in an earlier article by overlapping authors, published in Advanced Polymer Technology in 2018 under the title “A hydrophobic–hydrophilic cross-linked matrices for controlled release formulation of highly water-soluble drug venlafaxine: synthesis and evaluation studies.” That earlier work described a different drug delivery system for a different active compound, venlafaxine, yet apparently shared histological imagery with the salbutamol hydrogel study. When the same micrograph appears in papers describing distinct experiments on distinct drugs, at least one use of the image cannot be an honest record of the experiment it is presented alongside, a situation that strikes at the foundation of experimental reporting.

Adding to the pattern, the retraction notice reports that a number of other images in Figure 7 of the Polymer Bulletin paper appear highly similar to those in Figure 12 of a second earlier publication, a 2020 paper in AAPS PharmSciTech describing poloxamer-407 co-poly(2-acrylamido-2-methylpropane sulfonic acid) cross-linked nanogels for solubility enhancement of the antipsychotic drug olanzapine. Notably, that nanogel paper has itself already been retracted, a fact flagged in the retraction notice’s reference list. Taken together, the overlaps span at least three publications and multiple drug delivery platforms, suggesting that the same or near-identical toxicity images circulated across a family of related manuscripts rather than being generated fresh for each experiment.

For readers unfamiliar with how biomedical materials research is documented, the significance of histological figures deserves emphasis. In hydrogel toxicity studies, researchers typically implant or administer the material, harvest organs such as liver, kidney, heart, and lung, section the tissue, stain it—commonly with hematoxylin and eosin—and photograph it under a microscope. These images are the primary evidence that a formulation does not cause inflammation, necrosis, or other tissue damage. Because each experimental group generates its own set of slides, every image should be unique to its condition, animal, and time point. Image duplication between a control group and a treated group, or between entirely separate studies, therefore cannot be explained by ordinary technical variation. Modern forensic image analysis, which detects duplicated regions, spliced panels, and reused micrographs across journals, has made such duplications increasingly easy to detect and increasingly difficult for journals to ignore.

The retracted study itself had described an appealing materials-science concept. Gelatin, a biodegradable protein derived from collagen, is attractive for drug delivery because it is biocompatible, inexpensive, and can be chemically cross-linked to form hydrogels that swell in aqueous environments. A swellable hydrogel matrix can, in principle, control the release of a highly water-soluble drug such as salbutamol sulphate by regulating how quickly water penetrates the network and how the polymer chains relax, allowing the drug to diffuse out over an extended period rather than immediately. The paper reported characterization of these networks alongside toxicity evaluation intended to demonstrate biological safety. None of the retraction documentation disputes the underlying chemistry concept; what has been invalidated is the evidentiary record supporting the paper’s claims, particularly the safety data.

The human dimension of the case is also documented in the notice. Syed Faisal Badshah, one of the co-authors, does not agree to the retraction. The remaining authors—Naila Rafique, Mahmood Ahmad, Muhammad Usman Minhas, Nadia Shamshad Malik, and Kifayat Ullah Khan, affiliated with The Islamia University of Bahawalpur, the University of Sargodha, and Capital University of Science and Technology in Pakistan—have not responded to any correspondence from the editor or publisher about the retraction. Under Committee on Publication Ethics guidance, which Springer Nature journals follow, a retraction does not require unanimous author consent when the evidence of misconduct or unreliability is sufficiently strong; the journal’s editorial leadership can act unilaterally to protect the literature. The notice’s account of non-response and disagreement is a familiar profile in cases built on image integrity findings.

Retractions of this kind carry consequences well beyond the individual paper. Clinicians and formulation scientists who encounter the work may have incorporated its toxicity conclusions into reviews, meta-analyses, or the design of follow-up hydrogel systems for salbutamol, a drug used daily by millions of people with asthma and chronic obstructive pulmonary disease. Although a retracted paper’s claims about gelatin hydrogels are unlikely to have influenced approved clinical practice, the case illustrates why controlled-release research depends on trustworthy preclinical safety data. It also highlights the value of the linked-paper problem: when images recur across a group of manuscripts from the same laboratory, each retraction weakens confidence in the others, and editors increasingly treat such clusters as grounds for systematic review rather than case-by-case dismissal.

For the broader polymer and pharmaceutical sciences community, the episode is a reminder that characterization data—swelling ratios, drug release kinetics, and mechanical testing—are only as credible as the biological and imaging evidence that accompanies them. Journals now routinely screen submissions with image-integrity software, and readers can verify the retraction status of the article through the CrossMark badge on the publisher’s page and the linked retraction notice. The retracted article remains accessible online but is watermarked as retracted, and the notice directs readers to the original publication record. The scientific question the paper posed—whether gelatin-based swellable hydrogels can safely and effectively control the delivery of salbutamol sulphate—remains legitimate and open, but any future answer will need to rest on images and data that can withstand the scrutiny this study ultimately could not.

Subject of Research: Retraction of a study on gelatin-based swellable hydrogels for controlled delivery of salbutamol sulphate due to image overlap concerns

Article Title: Retraction Note: Designing gelatin-based swellable hydrogels system for controlled delivery of salbutamol sulphate: characterization and toxicity evaluation

Article References: Retraction Note: Designing gelatin-based swellable hydrogels system for controlled delivery of salbutamol sulphate: characterization and toxicity evaluation. (n.d.). https://doi.org/10.1007/s00289-026-06682-1

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06682-1

Keywords: retraction, gelatin hydrogels, salbutamol sulphate, controlled drug delivery, Polymer Bulletin, image duplication, toxicity evaluation, research integrity, swellable hydrogels, Springer Nature, histology, pharmaceutics