Thread Size and Polymer Composition of 3D Printed and Electrospun Wound Dressings Affect Wound Healing Outcomes in an Excisional Wound Rat Model.

Thread size and polymer composition are critical properties to consider for achieving a positive healing outcome with a wound dressing. Three-dimensional (3D) printed scaffolds and electrospun mats both offer distinct advantages as replaceable wound dressings. This research aims to determine if the thread size and polymer compositions of the scaffolds affect skin wound healing outcomes, an aspect that has not been adequately explored. Using a modular polymer platform, four polyester direct-write 3D printed scaffolds and electrospun mats were fabricated into wound dressings. The dressings were applied to splinted, full thickness skin wounds in an excisional wound rat model and evaluated against control wounds to which no dressing was applied. Wound closure rates and reduction of the wound bed width were not affected by the thread size or polymer composition. However, epidermal thickness was larger in wounds treated with electrospun dressings and was slightly affected by the polymer composition. Two of the four tested polymer compositions lead to delayed reorganization of granulation tissues. Moreover, enhanced angiogenesis was seen in wounds treated with 3D printed dressings compared to those treated with electrospun dressings. The results from this study can be used to inform the choice of dressing architecture and polymer compositions to achieve positive wound healing outcomes.

Elucidating the Molecular Interactions of Encapsulated Doxorubicin within a Nonionic, Thermoresponsive Polyester Coacervate.

Thermoresponsive polymers that display a lower critical solution temperature (LCST) are attractive drug delivery systems (DDSs) due to their potential to encapsulate and release therapeutics in a sustained manner as a function of temperature input. To attain the full potential of such DDSs, methods that illustrate the details of drug-polymer interactions are necessary. Here, we synthesized a nonionic, coacervate-forming, thermoresponsive polyester to encapsulate doxorubicin (Dox) and used solution state NMR spectroscopy and fluorescence microscopy techniques to probe the interactions between the polymer and Dox at the molecular level. The incomplete dehydration provides a matrix for encapsulation of sensitive therapeutics and preserving their activity, while the low hysteresis property of the polyester provides rapid transition from soluble to coacervate phase. Saturation transfer difference (STD) NMR revealed the Dox-polymer interactions within the coacervates. 1H-1H nuclear Overhauser effect spectroscopy (NOESY) cross-peak differences of Dox confirmed the Dox-polymer interactions. Diffusion-ordered spectroscopy (DOSY) revealed the slower diffusion rate of Dox in the presence of polyester coacervates. These studies illustrate how the state of the polyester (below and above LCST) affects the polyester-Dox interactions and offers details of the specific functional groups involved in these interactions. Our results provide a framework for future investigations aimed at characterizing fundamental interactions in polymer-based DDSs.

Body Composition Assessment in Male and Female Bodybuilders: A 4-Compartment Model Comparison of Dual-Energy X-Ray Absorptiometry and Impedance-Based Devices.

Graybeal, AJ, Moore, ML, Cruz, MR, and Tinsley, GM. Body composition assessment in male and female bodybuilders: a 4-compartment model comparison of dual-energy x-ray absorptiometry and impedance-based devices. J Strength Cond Res 34(6): 1676-1689, 2020-The purpose of this study was to examine the group and individual accuracy of body composition estimates obtained from multicompartment models, dual-energy x-ray absorptiometry (DXA), and several impedance-based devices in male and female bodybuilders. Twenty-seven male (n = 17; 4-compartment [4C] model fat-free mass index [FFMI]: 25.1 ± 1.8 kg·m; 4C body fat: 11.8 ± 4.4%) and female (n = 10; 4C FFMI: 18.3 ± 1.4 kg·m; 4C body fat: 19.7 ± 4.9%) bodybuilders underwent duplicate assessments using DXA, bioimpedance spectroscopy (BIS), electrical impedance myography (EIM), and 3 bioelectrical impedance analysis (BIA) devices. In addition to utilizing standard output, multicompartment models were generated. For each method, body fat %, FFM, and fat mass were compared with the reference 4C model for the evaluation of group and individual errors. The 3-compartment model with a BIS body water estimate produced the lowest standard error of the estimate, total error (TE), and 95% limits of agreement (LOA) for all variables, although some alternative methods had lower constant error (CE). In general, multicompartment models with BIS or multifrequency BIA body water estimates produced more accurate body composition estimates than single assessment techniques (i.e., DXA, BIS, EIM, and BIA). Single assessment techniques produced low CE and TE for some body composition variables. However, proportional bias was observed for DXA and BIS. All single assessment techniques produced LOA large enough to make the utility of these methods questionable in individual athletes. Appropriate caution should be used when interpreting and utilizing body composition estimates in muscular physique athletes, particularly at the individual level.

Time-restricted feeding plus resistance training in active females: a randomized trial.

BACKGROUND: A very limited amount of research has examined intermittent fasting (IF) programs, such as time-restricted feeding (TRF), in active populations. OBJECTIVE: Our objective was to examine the effects of TRF, with or without ß-hydroxy ß-methylbutyrate (HMB) supplementation, during resistance training (RT). METHODS: This study employed a randomized, placebo-controlled, reduced factorial design and was double-blind with respect to supplementation in TRF groups. Resistance-trained females were randomly assigned to a control diet (CD), TRF, or TRF plus 3 g/d HMB (TRFHMB). TRF groups consumed all calories between 1200 h and 2000 h, whereas the CD group ate regularly from breakfast until the end of the day. All groups completed 8 wk of supervised RT and consumed supplemental whey protein. Body composition, muscular performance, dietary intake, physical activity, and physiological variables were assessed. Data were analyzed prior to unblinding using mixed models and both intention-to-treat (ITT) and per protocol (PP) frameworks. RESULTS: Forty participants were included in ITT, and 24 were included in PP. Energy and protein intake (1.6 g/kg/d) did not differ between groups despite different feeding durations (TRF and TRFHMB: ∼7.5 h/d; CD: ∼13 h/d). Comparable fat-free mass (FFM) accretion (+2% to 3% relative to baseline) and skeletal muscle hypertrophy occurred in all groups. Differential effects on fat mass (CD: +2%; TRF: -2% to -4%; TRFHMB: -4% to -7%) were statistically significant in the PP analysis, but not ITT. Muscular performance improved without differences between groups. No changes in physiological variables occurred in any group, and minimal side effects were reported. CONCLUSIONS: IF, in the form of TRF, did not attenuate RT adaptations in resistance-trained females. Similar FFM accretion, skeletal muscle hypertrophy, and muscular performance improvements can be achieved with dramatically different feeding programs that contain similar energy and protein content during RT. Supplemental HMB during fasting periods of TRF did not definitively improve outcomes. This study was prospectively registered at clinicaltrials.gov as NCT03404271.

Duration-Dependent Effects of Passive Static Stretching on Musculotendinous Stiffness and Maximal and Rapid Torque and Surface Electromyography Characteristics of the Hamstrings.

Palmer, TB, Pineda, JG, Cruz, MR, and Agu-Udemba, CC. Duration-dependent effects of passive static stretching on musculotendinous stiffness and maximal and rapid torque and surface electromyography characteristics of the hamstrings. J Strength Cond Res 33(3): 717-726, 2019-This study aimed to examine the effects of stretching duration on passive musculotendinous stiffness and maximal and rapid torque and surface electromyography (EMG) characteristics of the hamstrings. Thirteen young females (age = 21 ± 2 years) underwent 2 passive straight-leg raise (SLR) assessments and 2 isometric maximal voluntary contractions (MVCs) of the hamstrings before and after 4 randomized conditions that included a control treatment and 3 experimental treatments of passive static stretching for 30-, 60-, and 120-second durations. Passive stiffness was calculated during each SLR as the slope of the final 10% of the angle-torque curve. Isometric peak torque (PT), rate of torque development (RTD), peak EMG amplitude (PEMG), and rate of EMG rise (RER) were extracted from each MVC. Results indicated that PT and PEMG were not affected (p = 0.993 and 0.422, respectively) by any of the experimental treatments. Rate of torque development and RER decreased from pre- to post-treatment for 120 seconds (p = 0.001 and 0.001) but not for the control (p = 0.616 and 0.466), 30- (p = 0.628 and 0.612), and 60-second (p = 0.396 and 0.815) interventions. The slope coefficient decreased from pre- to post-treatment for the 30- (p = 0.001), 60- (p = 0.002), and 120-second (p = 0.001) stretching interventions but not for the control (p = 0.649). Given the significant stiffness reductions and lack of changes in PT and RTD for the 30- and 60-second interventions, it may be advantageous for practitioners who are using hamstring passive stretching as part of a warm-up routine, to perform such stretching on their clients for short (30-60 seconds) rather than moderate (120-second) stretching durations.

Efficient Protein Encapsulation within Thermoresponsive Coacervate-Forming Biodegradable Polyesters.

Presented here is a novel method for encapsulating proteins into biodegradable, thermoresponsive coacervate-type polyesters. Bovine serum albumin (BSA) was efficiently incorporated into coacervate droplets via a simple thermoresponsive encapsulation mechanism. Tunable modular systems for encapsulation such as the one presented here may be useful in a range of protein delivery applications.