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    <element id="xbio_SeriesAWarrantsMember" name="SeriesAWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_OtherWarrantsMember" name="OtherWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_PubliclyTradedWarrantsMember" name="PubliclyTradedWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_NonEmployeeStockOptionsMember" name="NonEmployeeStockOptionsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_JSOPMember" name="JSOPMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_NonVestedEmployeeStockOptionMember" name="NonVestedEmployeeStockOptionMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_Plan401KMember" name="Plan401KMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_OfficeSpaceMember" name="OfficeSpaceMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_DNaseITechnologyMember" name="DNaseITechnologyMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_ClinicalTrialServicesMember" name="ClinicalTrialServicesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_DrGenkinMember" name="DrGenkinMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_ExerciseOfPurchaseWarrantsValue" name="ExerciseOfPurchaseWarrantsValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_ExerciseOfPurchaseWarrantsShares" name="ExerciseOfPurchaseWarrantsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_IssuanceOfCommonStockFromCashlessExerciseOfPurchaseWarrants" name="IssuanceOfCommonStockFromCashlessExerciseOfPurchaseWarrants" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_ConversionOfSeriesBPreferredStockToCommonStock" name="ConversionOfSeriesBPreferredStockToCommonStock" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_WarrantsPolicyTextBlock" name="WarrantsPolicyTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_NonprogramExpenses" name="NonprogramExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_OtherSegment" name="OtherSegment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_DisclosureTable" name="DisclosureTable" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" />
    <element id="xbio_DisclosureLineElements" name="DisclosureLineElements" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_ContractualObligationAddition" name="ContractualObligationAddition" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_AccruedResearchCosts" name="AccruedResearchCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_IncomeTaxReconciliationOthersReconcilingItems" name="IncomeTaxReconciliationOthersReconcilingItems" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_EffectiveIncomeTaxRateReconciliationAdjustments" name="EffectiveIncomeTaxRateReconciliationAdjustments" nillable="true" xbrli:periodType="duration" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_OperatingLossCarryforwardsExpirationDate1" name="OperatingLossCarryforwardsExpirationDate1" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_WarrantsExpiredDate" name="WarrantsExpiredDate" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_WarrantsForfeitedShares" name="WarrantsForfeitedShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="xbio_WarrantsExercisedShares" name="WarrantsExercisedShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
</schema>
