Biology subjects

de Guzman, R. C.

Publications and source records attributed to de Guzman, R. C..

8 recordsLinked to original sources

bioRxiv2026

Residual Hair Biomaterial Particulates Improve Dermal Regeneration and Combined with Electrical Stimulation Accelerates Skin Wound Closure

ObjectiveTo evaluate the effect of residual hair (RH) biomaterial particulates, biphasic electrical stimulation (ES), and their combination (RHES) on the kinetics and quality of skin wound healing. MethodEighteen adult albino mice received bilateral, splinted 10-mm full-thickness dorsal excisional wounds and were randomly assigned to one of three animal groups producing four wound-level treatment conditions: untreated control (-) (n = 12), RH (n = 12), ES (n = 6), and combined RHES (n = 6 wounds). Daily wound images were segmented using an AI-assisted workflow: a U-Net (ResNet34 encoder, ImageNet-pretrained, trained on a parallel single-expert tracing study with held-out validation Dice = 0.906) generated initial boundary predictions, each reviewed and corrected as needed. Wound size measures (perimeter, area, equivalent diameter [D_eq], circularity, aspect ratio) were normalized to the day-0 value of each wound and analyzed by linear mixed-effects regression with mouse identity as a random intercept and mouse body weight as a covariate. On day 7, wounds were excised, fixed, processed for histology, and analyzed by Massons trichrome (collagen content in granulation tissue) and GAP-43 immunohistochemistry (a marker of regenerative cellular activity). ResultsAll three treatments significantly accelerated wound closure compared to (-) (Day x Treatment interaction {chi}2(3) = 36.4, ***p < 0.0001). The closure-rate advantages on the log-D_eq scale were ES - 0.047/day (***p < 0.0001), RHES -0.029/day (***p = 0.0005), and RH -0.022/day (**p = 0.0015). By day 7, mean D_eq had decreased to 0.58 of the day-0 value in ES, 0.69 in RHES, 0.73 in RH, and 0.79 in (-). Tissue analyses revealed treatment-specific differences in healing quality: RH and RHES wounds contained 6.1x and 8.5x more collagen in granulation tissue than (-) (both **p = 0.002 vs (-); both **p = 0.009 vs ES), and showed approximately 16x and 27x greater mean GAP-43 expression than (-), respectively; the RHES increase remained significant after Bonferroni correction (adjusted *p = 0.042), whereas the RH increase did not (adjusted p = 0.058). ES alone did not significantly increase either collagen content or GAP-43 expression. Wound shape was more circular and more stable across days in RH-containing groups. Mouse body weight did not predict closure, whereas image-derived dryness, eschar coverage, and wound contraction were significant negative predictors of measured wound size. ConclusionES, RH, and RHES each significantly improve wound closure kinetics. The improvement appears mechanistically distinct: ES principally accelerates closure rate, while RH principally enhances tissue-level regenerative markers (collagen deposition and GAP-43 expression). RHES combines both advantages. Declaration of interestDr. de Guzman is the inventor on a pending patent covering residual hair biomaterial methods and use and a provisional patent on powderized version, both owned by Hofstra University, and is the founder of a company developing wound care products based on the technology. The study was conducted independently. Data are available upon reasonable request.

bioengineering↗

bioRxiv2026

Intramuscular Delivery of BMP-2 and Increasing Doses of LECT-1 Using Keratin-PEG Gels for Ectopic Tissue Differentiation

Producing bone and cartilage in a controlled and localized manner remains a significant challenge in regenerative medicine. This study investigated the ability of keratin- and polyethylene glycol (PEG)-based degradable hydrogels to deliver bone morphogenetic protein 2 (BMP-2) and leukocyte cell-derived chemotaxin 1 (LECT-1; also known as chondromodulin-1) intramuscularly to induce ectopic tissue formation. Adult male CD-1 mice received intramuscular implants of keratin-PEG gels containing a fixed dose of BMP-2 and increasing amounts of LECT-1. After two weeks, implants and surrounding muscle were analyzed using computed tomography (CT) and histology. The results showed that BMP-2 is necessary for forming new bone and cartilage, whereas LECT-1 alone appeared to trigger muscle dedifferentiation without ossification or chondrogenesis. Co-delivery of BMP-2 and LECT-1 enhanced bone and cartilage formation in a dose-dependent manner: higher LECT-1 doses led to proportionally more ectopic cartilage (linear correlation, r2 {approx} 90%), while bone formation peaked at the third LECT-1 dose at approximately twice the volume of the BMP-2-only group. These findings indicate that muscle-resident cells may be capable of reverting and switching to mesenchymal lineages, recapitulating endochondral ossification. The platform offers a promising strategy for growing bone and cartilage autografts within skeletal muscle bundles. Impact StatementThis study presents a novel strategy for inducing ectopic bone and cartilage formation by delivering BMP-2 and LECT-1 from keratin-PEG hydrogels into skeletal muscle. The findings suggest that muscle-resident cells can dedifferentiate and transdifferentiate into mesenchymal lineages, enabling controlled ectopic tissue regeneration. This approach may inform future tissue engineering therapies in which autografts are harvested from within the body, using skeletal muscle as an in vivo tissue incubator.

bioengineering↗

bioRxiv2026

Biomechanics of chemically treated hair for continuous 1D strands

Human hair is a keratin-based fiber with mechanical properties relevant to load-bearing biomaterials; however, its smooth cuticle limits fiber-fiber cohesion during textile-style processing. This study examines how controlled chemical decuticularization influences surface morphology and tensile behavior of intact human hair assembled into continuous one-dimensional (1D) strands. Hair was treated with oxidative bleach, sodium hydroxide (NaOH), or formic acid (FA), carded, and spun using a standardized protocol. SEM imaging showed treatment-dependent surface disruption, from minimal cuticle modification (bleach) to partial scale lifting (NaOH) and extensive cuticle removal (FA). Tensile testing revealed significant differences in Youngs modulus, ultimate tensile strength (UTS), and elongation at break (EAB) across treatments (ANOVA, p < 0.05). NaOH-treated strands exhibited the highest modulus (207 MPa), UTS (34 MPa), and moderate extensibility (28%), whereas bleach- and FA-treated strands showed reduced stiffness and strength. Compared with reference yarns, NaOH-treated strands approached the stiffness of wool and retained greater extensibility than cotton. These findings support a processing window in which partial decuticularization enhances fiber cohesion while preserving mechanical integrity. The resulting 1D strands provide a potential building block for woven biomesh structures, motivating further evaluation of durability, cyclic behavior, multi-ply configurations, and computational modeling.

bioengineering↗

bioRxiv2024

Anti-fibrotic Effects of Atorvastatin Delivered via Keratin-based Hydrogels

Implantations of degradable biomaterials for drug delivery or restoration and regenerative medicine cause fibrosis and acute inflammation which may lead to chronic side effects. Additionally, the fibrous encapsulation can itself inhibit the local cells from proliferating and forming new healthy tissue. Current drug delivery models require a new method to decrease the adverse effects following implantation of biomaterials in patients and inhibit the activation signaling sent to quiescent fibroblasts. This research details the novel chemical and physical properties of reduced keratin (KTN) hydrogels extracted from residual human hair with sheared cuticle layers, obtained from barbershops and beauty salons. KTN hydrogels with and without calcium ions conjugated with atorvastatin (Ator), which is thought to affect TGF-{beta} signaling pathways directly by competitively inhibiting key signal transmitters and cellular responses, were investigated via electron microscopy, absorbance spectroscopy, and computational modeling and simulation to observe the proliferative inhibition of fibroblastic cells in comparison to the alginate hydrogel controls. Hydrogel extracts were tested for non-cytotoxic effects via L929 adipose fibroblast cell culture following ISO 10993-5 standard for safety of medical device biomaterials. Two cell models were exposed to increasing serial concentrations of Ator to evaluate the half maximal effective concentration (EC50). For quiescent fibroblasts, Ators EC50 was observed at 368 M in PBS. For mesenchymal stem cells (MSCs), Ators EC50 was observed at 209 M in PBS. The mass of drug was normalized in all groups after calculating their timed absorption and release, and KTN hydrogels conjugated with calcium ions and Ator (ATCK) completely absorbed the drug < 0.5 h while KTN hydrogels with Ator alone (ATKR) completely absorbed the drug at 1h. After 7d in PBS, ATCK released Ator at 2.2 {+/-} 0.7% while Ator in calcium alginate spheres (ATLG) was released at 7.8 {+/-} 1.1% and ATKR released 11.2 {+/-} 4.3% of drug. On-going research focuses on other active fibroblastic cell types and in vivo experimentation to observe foreign body response in subcutaneous mouse tissue.

bioengineering↗

bioRxiv2024

Biocompatibility of KAPs-Depleted Residual Hair

This work is an in-depth investigation of the in vitro and in vivo biocompatibility of processed and treated residual human hair samples with intact cuticle layers. The specimens included oxidized hair with no melanin (BLH) and hair with medium-(M-KAP) and low-(L-KAP) levels of keratin associated proteins (KAPs), confirmed through gel electrophoresis, electron microscopy, and trichrome histological staining, in comparison to the untreated regular hair (REG) control. All hair groups, high KAPs (H-KAPs: REG and BLH), M-KAP, and L-KAP, were found to be non-cytotoxic in the adipose fibroblast cell lines response to their extracts based on the ISO 10993-5 medical device biomaterial testing standard. In vivo mouse subcutaneous implantation (ISO 10993-6, local effects) at 2 weeks showed that the samples caused a foreign body response (FBR) with a thin fibrous encapsulation at a mean value of 28% relative skin dermis thickness; but notably, the L-KAP implant mitigated a statistically significant decrease in FBR area compared to H-KAPs (REG and/or BLH) and a lower number of cells, including immune cells of mostly macrophages and mast cells on the biomaterials surface, normalized to implant and tissue coverage. In the bulk of the capsules, blood vessels and collagen extracellular matrix densities were similar among groups. These findings suggest that small globular KAPs diffuse out of the cortex to the host-biomaterial interface which induce a slightly elevated FBR but limited to the implants surface vicinity. On-going follow-up research focuses on purer keratin-based macromolecularly organized residual hair biomaterials, those with depleted KAPs, for drug-delivery gel implants as they are deemed the most biocompatible. Statement of SignificanceHuman hair is an abundant biological product that is regularly discarded and wasted but has the potential to be a clinical implantable allograft biomaterial. There are currently just two FDA class II-510(k)-approved medical devices from hair, limited to surface / skin wound care use, and no class III-PMA or biologics-BLA implants. Also, these products and those in research and development phases are based on soluble keratin and KAPs extracts utilizing tedious processing conditions and requiring oxidation reaction for reassembly into gels and scaffolds. Here we describe that the insoluble residual hair biomaterials with organized keratin structure, higher-degree of disulfide crosslinks, and particularly those with depleted KAPs have increased biocompatibility based on pre-clinical ISO 10993 standards. This novel natural biomaterials are now being developed as drug-delivery implantable gels for clinical applications.

bioengineering↗

bioRxiv2022

Reduced fibrous capsule elastic fibers of biologic ECM-enveloped CIEDs in minipigs fitted with a compression mechanics model

BACKGROUNDFibrous capsules (Fb) in response to cardiovascular implantable electronic devices (CIEDs), including a pacemaker (P) system, can produce patient discomfort and difficulties in revision surgery due partially to their increased compressive strength, previously linked to elevated tissue fibers. OBJECTIVETo quantify structural proteins, determine if biologic extracellular matrix-enveloped CIEDs (PECM) caused differential Fb properties, and to implement a realistic mechanical model. METHODSRetrieved Fb (-P and -PECM) from minipigs were subjected to biomechanical (shear oscillation and uniaxial compression) and histological (collagen I and elastin) analyses. RESULTSFb-PECM showed significant decreases compared to Fb-P in: low strain-loss modulus (390 vs. 541 Pa) across angular frequencies, high strain-compressive elastic modulus (1043 vs. 2042 kPa), and elastic fiber content (1.92 vs. 3.15 g/mg tissue). Decreases in elastin were particularly noted closer to the implants surface (Fb-PECM = 71% vs. Fb-P = 143% relative to dermal elastin at mid-tangential sections) and verified with a solid mechanics hyperelasticity with direction-dependent fiber viscoelasticity compression simulation (r2 [≥] 98.9%). CONCLUSIONSThe biologic envelope composed of decellularized porcine small intestine submucosa ECM for CIEDs promoted fibrous tissues with less elastic fibers. Novel compression modeling analyses directly correlated this singular reduction to more desirable subcutaneous tissue mechanics.

bioengineering↗

bioRxiv2018

Compressive strengths of PEG gels with glycerol and bioglass particles

Poly(ethylene glycol) (PEG)-based materials can potentially be used as biomechanical matrices for regenerative medicine implants including the replacement of intervertebral (IV) discs. Glycerol and other plasticizers (low-MW PEG, propylene glycol, and sorbitol) were added to the bulk PEG matrix, gelled using chemical and photochemical methods at different temperature and pressure settings, and compression properties acquired and analyzed. Incorporation of surface bioactive glass particles shortened the blood clotting time, while alginate and laponite additives improved the gels mechanical properties to 645 kPa compressive modulus, 12% yield strain, and 79 kPa yield strength. This IV disc-modeled system endured the cyclic loading and unloading test indicative of an elastic response; but required improvement of its biomechanical tolerance.

bioengineering↗

bioRxiv2018

PABA Release from Chitosan-PCL with Induced Electric Current

Controlled drug delivery systems such as the stimulation-based biomaterial scaffolds for sequestration and release of drugs offer safety and regulated therapeutic approach. In this study, the drug: para-aminobenzoic acid (PABA) was absorbed into a crosslinked chitosan and poly(caprolactone) (PCL) hydrogel and its release kinetics quantified under different conditions. It was experimentally-observed that the higher the pH (or the more basic the pH), the slower the PABA saturation release trended over time. At the acidic environment of pH 4, PABA was released the fastest, and enhanced by the degradation of chitosan-PCL gel. When a constant electric current of 0.6 mA sa applied, PABA release was induced at pH 10. However, at pH 7, PABA was stably-bound to the chitosan-PCL matrix, with or without the external current. The selective sequestration of PABA at basic pH and its stimulated release via electric current application can be further explored for clinical translatability.

bioengineering↗