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 Notably, that nanogel paper has itself already been retracted, a fact flagged in the retraction notice’s reference list.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

The original article, published on 17 December 2019 in Polymer Bulletin volume 77, pages 6063 to 6083, reported the development and optimization of hydrogel networks built from pectin, a naturally occurring polysaccharide most familiar to consumers as the gelling agent in jams and jellies. In pharmaceutical science, pectin has attracted intense interest because it is biocompatible, biodegradable, inexpensive, and derived from renewable plant sources such as citrus peel and apple pomace. The research team, led by authors affiliated with Government College University Faisalabad, the University of Sargodha, The University of Lahore, and The Islamia University of Bahawalpur in Pakistan, set out to tune the swelling behavior, gel fraction, and drug release kinetics of these hydrogels so that nifedipine could be released steadily over an extended period rather than in a sudden burst.

Nifedipine is a calcium channel blocker widely prescribed for hypertension and angina, and its delivery profile matters enormously for patient safety. The drug is notoriously photolabile and poorly water soluble, and conventional immediate-release formulations have been associated with sharp drops in blood pressure and reflex tachycardia. Controlled-release matrices, including hydrogel systems, are designed to smooth out these peaks and troughs by allowing water to penetrate the polymer network, dissolve the drug, and then diffuse outward through the swollen mesh at a rate governed by crosslinking density, polymer composition, and mesh size. A pectin-based system with adjustable properties would, in principle, let formulators dial in the desired release rate simply by changing formulation variables, a proposition with genuine commercial and clinical appeal.

That is precisely why the concerns flagged by the Editor-in-Chief strike at the heart of the paper’s credibility. According to the expression of concern, Figure 5 of the pectin hydrogel article appears to be identical to Figure 2c in a separate 2018 publication on chondroitin sulfate-based hydrogels of loxoprofen, which appeared in Carbohydrate Polymers. The overlap involves two different polymers, two different drugs, and two different experimental contexts, making the apparent duplication particularly troubling. In materials characterization, figures typically present spectroscopic traces, swelling curves, or release profiles that are unique to a specific formulation under specific conditions. When the same figure surfaces in studies of unrelated polymer-drug combinations, it raises the possibility that the underlying experiments were not performed as described, or that images were reused to fill gaps in the data record.

The second concern is subtler but no less consequential. The Editor-in-Chief notes that the acrylic acid trace in Figure 2 of the pectin study appears highly similar to the trace in Figure 2 of yet another 2018 paper, this one describing a cross-linked sodium alginate-g-poly(acrylic acid) hydrogel network for the delivery of loxoprofen sodium, published in Advanced Polymer Technology. In that case, the similarity persists even though the x-axis appears to have been shifted slightly. Fourier transform infrared spectroscopy and related analytical traces are fingerprints of chemical structure, and while spectra of related acrylate-based networks can resemble one another, a near-duplicate trace with a minor axis shift suggests digital manipulation rather than independent measurement. Shifting an x-axis is a classic red flag in image-integrity investigations because it can make copied data look superficially distinct while preserving the underlying pattern.

Compounding these figure-level concerns is the authors’ response, or lack thereof. The expression of concern states that the authors have not provided the original scanning electron microscopy images, both before and after expansion, upon request. SEM micrographs are central evidence in hydrogel characterization, revealing pore morphology and network structure that correlate directly with swelling and diffusion behavior. When authors cannot or will not produce the raw image files underlying published micrographs, editors and readers lose the ability to verify that the images depict the samples in question. The notice also records that the authors have not responded to any correspondence from the editor or publisher regarding the expression of concern, leaving the issues unresolved and the scientific record in limbo.

Editorial Expressions of Concern occupy an important and often misunderstood niche in scholarly publishing. Unlike a retraction, which withdraws a paper’s findings from the literature, an expression of concern signals that doubts exist but that an investigation is incomplete, inconclusive, or ongoing. Journals typically issue them when institutional inquiries are pending, when authors are unresponsive, or when the evidence of problems is strong but not yet definitive. Readers are advised in this case to interpret the results with caution, which in practical terms means that researchers citing the paper should acknowledge its contested status and that clinicians or formulators should not rely on its reported optimization data without independent confirmation. The notice is linked to the original article through Crossmark, Springer Nature’s version-of-record update service, ensuring that anyone accessing the 2019 paper will see the alert.

The episode also shines a light on the broader challenge of image integrity in polymer and pharmaceutical sciences, fields that generate enormous volumes of spectroscopic traces, micrographs, and kinetic curves. Duplicate and manipulated figures have been documented across disciplines, and automated screening tools now routinely flag similarities that might once have escaped notice. The two earlier papers referenced in the expression of concern, both involving overlapping authorship with the pectin study, illustrate how concerns can cluster around related bodies of work. When a single figure or trace appears in multiple publications describing different chemical systems, the credibility of all affected papers comes into question, because at least some of the published data cannot reflect real experiments as described.

For the field of natural polymer drug delivery, the stakes extend beyond one paper. Pectin, alginate, chondroitin sulfate, and related polysaccharides remain genuinely promising scaffolds for controlled release, and well-executed studies continue to advance the area. But the credibility of that literature depends on the verifiability of individual results, and expressions of concern like this one serve as a reminder that optimization claims, release profiles, and structural characterizations must rest on data that can withstand scrutiny. Whether the 2019 pectin-nifedipine study is ultimately retracted, corrected, or exonerated, the case underscores a simple principle on which the entire enterprise of pharmaceutical materials science depends: the figures in a paper must be the honest record of the experiments the paper claims to describe.

Subject of Research: An Editorial Expression of Concern raised over a pectin-based hydrogel study for controlled nifedipine delivery in Polymer Bulletin

Article Title: Editorial Expression of Concern (EEoC): Pectin-based hydrogels with adjustable properties for controlled delivery of nifedipine: development and optimization

Article References: Editorial Expression of Concern (EEoC): Pectin-based hydrogels with adjustable properties for controlled delivery of nifedipine: development and optimization. (n.d.). https://doi.org/10.1007/s00289-026-06680-3

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06680-3

Keywords: pectin hydrogels, nifedipine, controlled drug delivery, Editorial Expression of Concern, Polymer Bulletin, research integrity, image duplication, scanning electron microscopy, polysaccharide polymers, drug release kinetics, Springer Nature, pharmaceutics