Light sensitive hydrogels have been employed in a broad variety of settings and rely on light sensitive functionalities incorporated into the hydrogel network. Two well-known light sensitive moieties are the ortho-nitrobenzyl group (oNB) and its ortho-nitroveratryl analog. Although ortho-nitrobenzyl and ortho-nitroveratryl groups have been employed successfully many times in a variety of studies, they have low to very low quantum yields and during photocleavage toxic nitroso adducts are formed. Therefore we are curious to employ phenacyl based photo cleavable hydrogel crosslinkers (Figure and 1D), as these have a significantly higher quantum yield. Photo responsive phenacyl moieties have been applied to photocage thiols, control the degree of swelling in polymer coatings, induced light triggered folding of polymers chains and to photocage a drug such as chlorambucil. 26 Chemotherapy is one of the most important strategies to treat cancer. However, the administered dose of any particular drug is often low due to its toxicity and accompanying side effects. To mitigate these limiting factors and improve the efficacy of chemotherapeutic drugs, smart drug delivery systems are employed. Responsive hydrogel networks can be used for controlled delivery. Hydrogels are able to covalently or non-covalently store a variety of anticancer drugs and show triggered release in the human body. Alternatively, monoclonal antibodies or antibody-drug conjugates (ADC) are employed to selectively target malignant tumour cells and induce cell death. Controlled antibody release can improve therapy as the total administered dose is low, on target drug concentrations are high and systemic drug exposure is low which helps to reduce side effects. Release mechanisms rely on a variety of internal and external triggers, including hydrolysis, 30 temperature, ultrasound, (UV) light or enzymatic activity. Also, passive release mechanisms are employed to deliver antibodies from hydrogels, were the degree of hydrogel branching and crosslink density determine the release profile of the loaded proteins. Here, we present light cleavable dextran based hydrogels loaded with either doxorubicin, bovine serum albumin (BSA) or human Immunoglobulin G (IgG), which release their cargo when triggered by (UV-A/C) light. Photosensitivity in the Cerenkov irradiation window is introduced by crosslinking alkyne modified dextran with bis-azide phenacyl C1 or C2 using standard Cu-click conditions (Figure ).