Flexible Electromagnetic Coil Patch-enhanced Healing of Full-Thickness Skin Wounds in Rats

Summary

This protocol demonstrates a method for creating full-thickness circular skin wounds in rats and enhancingtheirhealingusing a flexible copper coilpatch that delivers apulsedelectromagnetic field.

Abstract

Chronic and large skin wounds present significant clinical challenges due to delayed healing and high infection risk. Pulsed electromagnetic field (PEMF) therapy is a non-invasive approach that can promote tissue repair. This study describes a reproducible rat wound model protocol using a flexible printed copper coil patch connected to a custom PCB controller to deliver localized PEMF stimulation to full-thickness dorsal wounds. The contralateral wound served as an untreated control. Healing progression was assessed through regular photography and wound area measurements. The protocol provides a practical, adaptable system for evaluating and optimizing PEMF-based therapies in vivo across various conditions, with a focus on localized application and parameter adjustment for regenerative medicine. Parameter selection was based on an orthogonal CCK-8 screen of fibroblast proliferation that tested 0.25-1.3 mT, 10-40 Hz, and 30-90 min/day; main-effect analysis identified 1.3 mT, 30 Hz, and 60 min/day as the optimal levels, which were adopted for in vivo testing.

Introduction

Chronic cutaneous wounds (such as diabetic ulcers) are a growing health concern, often leading to impaired healing, infection, or amputation¹. Traditional treatments can be prolonged and costly, prompting interest in adjunctive therapies that can speed up tissue repair². Electromagnetic field therapy is one such approach, which is non-invasive and has demonstrated pro-healing effects in both preclinical and clinical settings^2,3,4,5. Pulsed electromagnetic fields (PEMFs) in the extremely low-fre....

Protocol

All animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Jiangnan University (JN. No2025-0630S0360-915[408]). We implemented the protocol using male SD rats (6-8 weeks old, approximately 200-250 g). Prior to experimentation, rats were individually housed with free access to food and water, maintained on a 12 h light/dark cycle, in accordance with the Guide for the Care and Use of Laboratory Animals.

1. Creation of full-thickness excisional wounds

1. Prepare the animal and surgical field.
   1. Induce anesthesia with 3-4% isoflurane in an induction chamber. After loss o....

Results

In this full-thickness rat wound model, daily PEMF therapy via a flexible coil patch resulted in significantly faster wound closure compared to controls. To rigorously evaluate the effect, rats were allocated into three groups based on the experimental design outlined in the Protocol section: a within-subject control group (where each rat had one PEMF-treated wound and one contralateral untreated wound, data pooled for analysis), a sham control group (PATCH: wound covered with an unpowered coil), and an untreated control.......

Discussion

Critical steps include creating symmetric full-thickness wounds, ensuring the coil patch lies flat over a sterile barrier without gaps, and maintaining consistent daily exposure; deviations can reduce field delivery and increase variability in healing outcomes.

This work has several limitations that should be considered when interpreting the findings and assessing translational potential. First, the protocol was demonstrated in healthy male SD rats (6-8 weeks, 200-250 g) with acute excisional .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
96-well cell culture plates	BaiDi	H908002	For CCK-8 assay
ADHESION MICROSCOPE SLIDES	CITOTESTO	P/N.80312-3161	Equipment for  H&E/Masson staining
Analgesic (Lidocaine Hydrochloride Injection)	HUAMU	70011657	Opioid analgesic, 4 mg/kg (for pain control)
Anesthesia machine	RWD Life Science (Shenzhen, CN)	R520-Iso	Isoflurane vaporizer with oxygen supply
Automated immunohistochemical staining machine	Leica	21.2201	automated immunohistochemical staining
Biopsy punch (20 mm)	Integra Miltex	#33-37	Circular skin punch, 2 cm diameter
Camera, digital	Huawei Mate 70 pro	N/A	≥12 MP for wound imaging
CD31 antibody	Abcam	ab182981	Endothelial marker for IHC (Figure 4B)
CD34 antibody	Abcam	ab81289	Endothelial marker for IHC (Figure 4B)
Cell Counting Kit-8 (CCK-8)	Biosharp	BS350B	Used for in vitro PEMF parameter screening (OD450)
Cell culture dish (10 cm)	BaiDi	H802004	10 cm (100 mm) tissue culture dish for fibroblast culture
Cell culture medium (e.g., DMEM + FBS)	BaiDi	L100-500	For fibroblast culture in CCK-8 screen
CO2 incubator	Thermo	BB150-2TCS-L	For fibroblast culture
Coil, flexible copper	Custom-fabricated (in-house)	N/A	Spiral printed coil (5 cm diam., polyimide)
Controller board (PEMF generator)	Custom-built (in-house design)	N/A	Custom PCB, drives coil at 30 Hz, ~1.3 mT
Electric hair clipper	Wahl or Oster (pet grooming)	Model 9160	Animal grooming clipper for shaving fur
Elizabethan collar (rodent)	MukeBio	MK-EC-01	Prevent wound interference
Embedding Station	Epredia HistoStar	A81000002	Processing for histology (if performed)
face mask	vedeng	V531596	Maintain anesthesia
Fibroblasts (cell line L929)	Procell	CL-0137	Cells used for CCK-8 proliferation screening
Finite element simulation software (e.g., COMSOL Multiphysics)	COMSOL	CM010004	Magnetic field simulation (Figure 5B-C)
Flexible aluminum strip splint	deargo	1592	Support to prevent coil displacement
Forceps	Majestic	01625	For handling skin and dressings during surgery
Hematoxylin & Eosin (H&E) Automatic dyeing and sealing uni	DRS-Prisma-P+FILM	61770249	Consumable for routine histology staining
Image analysis software	National Institutes of Health	Version 1.54	For wound area measurement (e.g., ImageJ)
Image analysis software	National Institutes of Health	Version 1.54	For wound area measurement (e.g., ImageJ)
Induction chamber	RWD Life Science (Shenzhen, CN)	802-00132-00	Isoflurane anesthesia induction
Infrared thermal imaging camera	HIKMICRO	H11	Monitor coil surface temperature (Figure 5A)
Iodine Povidone Disinfectant 10%	HYNAUT	N/A	Skin antiseptic (iodophor)
Isoflurane	RWD Life Science (Shenzhen, CN)	20037015	Inhalation anesthetic (USP grade)
Lidocaine Injection 10%	SANMA	N/A	For postoperative analgesia
Masson's trichrome staining kit	BASO	C250202	Consumable for collagen/ECM visualization
Medical Skin Marker and Ruler	Tondaus	N/A	Include scale in wound photographs
Microplate reader	Thermo	A51119500C	For OD450 measurement in CCK-8 assay
Microtome	Epredia HM 340E	23900670	Sectioning for histology/IHC (if performed)
Polyformaldehyde tissue fixative	share-bio	SB-C009	Fixation of animal tissue specimens
Rat housing cage	FengQiao	CP-JM	Standard rat housing cage for individual housing.
Rats, Sprague Dawley (male, 6–8 weeks)	WeiJingyu SUZHOU	SCXK2024-0004	200–250 g; individually housed; IACUC-approved use
Scalpel	Jinhuan	35W0602	For excisional wound creation
Semipermeable film dressing	ZD	Q20189	Alternative wound barrier
Statistical analysis software (e.g., GraphPad Prism or R)	Software Mackeiv	10.6.9(890)	Two-way ANOVA and post hoc multiple comparisons
Sterile gauze	ZD	3141626	Wound dressing/protective barrier
Sterile surgical drapes	ZD	V271617	To drape the surgical field after skin prep
Surgical scissors	Majestic	01627	For excisional wound creation
Syringes and needles	MINANK	20193141643	For subcutaneous analgesic administration
Whole-slide scanner	3DHISTECH	N/A	Digital slide scanning