Sorbents can tailor nitrogen release from organic wastes to match the uptake capacity of crops.

Delivering nutrients from mineral or organic fertilizers out of synchrony with crop uptake causes inefficiencies and pollution. We explore methodologies for evaluating sorbents as additives to organic agricultural wastes to retain nitrogen in an exchangeable form and deliver at rates that approximate the uptake capacity of roots. Focussing on ammonium (NH4+) as the main inorganic nitrogen form in the studied wastes (sugarcane mill mud, poultry litter), we tested geo-sorbents and biochar for their ability to retain NH4+. Sorption capacity was ranked palagonite < bentonite, biochar, vermiculite < chabazite, clinoptilolite (5.7 to 24.3 mg NH4+ g-1 sorbent). Sorbent-waste formulations were analysed for sorption capacity, leaching and fluxes of NH4+. Ammonium-sorption capacity broadly translated to sorbent-waste formulations with clinoptilolite conferring the strongest NH4+ attenuation (80%), and palagonite the lowest (7%). A 1:1 ratio of sorbent:waste achieved stronger sorption than a 0.5:1 ratio, and similar sorption as a 1:1.5 ratio. In line with these results, clinoptilolite-amended wastes had the lowest in situ NH4+ fluxes, which exceeded the NH4+ uptake capacity (Imax) of sugarcane and sorghum roots 9 to 84-fold, respectively. Less efficient sorbent-waste formulations and un-amended wastes exceeded Imax of crop roots up to 274-fold. Roots preferentially colonized stronger sorbent-waste formulations and avoided weaker ones, suggesting that lower NH4+ fluxes generate a more favourable growth environment. This study contributes methodologies to identify suitable sorbents to formulate organic wastes as next-generation fertilizers with view of a crop's nutrient physiology. Efficient re-purposing of wastes can improve nutrient use efficiency in agriculture and support the circular nutrient economy.

Effects of electric fields on human mesenchymal stem cell behaviour and morphology using a novel multichannel device.

The intrinsic piezoelectric nature of collagenous-rich tissues, such as bone and cartilage, can result in the production of small, endogenous electric fields (EFs) during applied mechanical stresses. In vivo, these EFs may influence cell migration, a vital component of wound healing. As a result, the application of small external EFs to bone fractures and cutaneous wounds is actively practiced clinically. Due to the significant regenerative potential of stem cells in bone and cartilage healing, and their potential role in the observed improved healing in vivo post applied EFs, using a novel medium throughput device, we investigated the impacts of physiological and aphysiological EFs on human bone marrow-derived mesenchymal stem cells (hBM-MSCs) for up to 15 hours. The applied EFs had significant impacts on hBM-MSC morphology and migration; cells displayed varying degrees of conversion to a highly elongated phenotype dependent on the EF strength, consistent perpendicular alignment to the EF vector, and definitive cathodal migration in response to EF strengths ≥0.5 V cm(-1), with the fastest migration speeds observed at between 1.7 and 3 V cm(-1). We observed variability in hBM-MSC donor-to-donor responses and overall tolerances to applied EFs. This study thus confirms hBM-MSCs are responsive to applied EFs, and their rate of migration towards the cathode is controllable depending on the EF strength, providing new insight into the physiology of hBM-MSCs and possibly a significant opportunity for the utilisation of EFs in directed scaffold colonisation in vitro for tissue engineering applications or in vivo post implantation.

Biomechanical evaluation of double Krackow sutures versus the three-loop pulley suture in a canine gastrocnemius tendon avulsion model.

OBJECTIVE: To compare two Krackow sutures with a three-loop pulley suture for the reattachment of canine gastrocnemius tendons, using a tendon avulsion model. STUDY DESIGN: In vitro biomechanical study. METHODS: Ten paired gastrocnemius tendons were severed at their insertions on the calcaneal tuberosity and repaired with either two modified Krackow sutures or a modified three-loop pulley suture. Sutures were placed in the tendon ends and through diverging bone tunnels in the medial and lateral processes of the calcaneal tuberosity. Tensile loads required to (a) create a 3-mm gap and (b) induce construct failure were measured. RESULTS: The mean load to achieve a 3-mm gap was 77.22 ± 9.72 and 55.85 ± 9.91 N, and to result in construct failure was 106.88 ± 12.74 and 80.86 ± 12.23 N for the Krackow and three-loop pulley suture patterns, respectively. These differences were statistically significant (P < 0.001 and P = 0.001, respectively). CONCLUSION AND CLINICAL RELEVANCE: Two Krackow sutures were superior to the three-loop pulley pattern in both resistance to 3-mm gap formation and load to failure in a canine gastrocnemius avulsion model. The prevention of gap formation is critical for the success of tenorrhaphy. These results indicate that a suture pattern using two Krackow sutures may be clinically superior to the three-loop pulley suture pattern in the repair of canine gastrocnemius avulsion. Further work is required to determine if this superiority is mirrored in the repair of other tendon avulsion or laceration scenarios.